tag:blogger.com,1999:blog-60800712902359050562024-03-12T18:07:21.991-07:00Blather 'bout BikesJust a place for me to post in a single location my various musings and obsessions about bicycle technology.Tom Anhalthttp://www.blogger.com/profile/08175472546482777614noreply@blogger.comBlogger27125tag:blogger.com,1999:blog-6080071290235905056.post-65240644286909517882020-04-19T15:03:00.001-07:002020-04-19T15:20:58.505-07:00Some Additions to the Gravel Tire List<br />
Well, after my last round of roller testing, and the quite good performance of the Conti Terra Speed, I was curious about how the seemingly only slightly more "knobby" Terra Trail would perform. So, I bought one to test out. At the same time, an acquaintance from the Slowtwitch forum, Rob Pickels, informed me that he had a pair of the new tubeless-ready Challenge Gravel Grinder Pro HTLR (that's a mouthful!) tires that he decided not to use and would send to me if I was interested in testing them out. I had been curious about the GG Pro HTLR since it had come out, since some of the reports were that the coating used by Challenge to make the tire more air-tight was butyl...and if that was the case, I didn't have high hopes that it would perform as well as their non-TLR GG Pro. I was especially discouraged when I found out they were listing it as having 2 puncture resistant layers ("2xPPS"), which is what the non-TLR version had. It didn't make sense to me...if the tire is intended to be run with sealant, then a reasonable approach would be to eliminate one, or even both, of the puncture protection strips since they aren't as critical for a tubeless w/sealant approach, and all they do is slow down a tire.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiId0dtLOGsak2yjqUpHAzwYjcxeIiuGfEDsARFgViBNRHfR4v5kWokdR-EHMw5NmwoojYlVQ6ciIbbkz73ArJdIQniSj0-7o7Gy_NohVzgN9vlu7Ds5Zn4Gq94tUlv0dB83NDuVLe5c0o/s1600/20200418_115927.jpg" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="1600" data-original-width="900" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiId0dtLOGsak2yjqUpHAzwYjcxeIiuGfEDsARFgViBNRHfR4v5kWokdR-EHMw5NmwoojYlVQ6ciIbbkz73ArJdIQniSj0-7o7Gy_NohVzgN9vlu7Ds5Zn4Gq94tUlv0dB83NDuVLe5c0o/s640/20200418_115927.jpg" width="360" /></a>So, once I got my hands on Rob's tires, here's what I found: to my "feel", the coating used on both the outer sidewalls and inner surface of the appears to be more like a latex coating, rather than butyl (thank science!). Additionally, it looks like the HTLR beads have an additional "rub layer" coated with a black rubber (THAT could be butyl...and is there to address the cutting issues with rims like ENVEs). Lastly, on the inside of the casing there is NOT a red material layer like there is on the non-TLR models. I always assumed that was the PPS layers...and now I'm wondering if, in fact, the HTLR models actually eliminated the PPS layers? Take a look here: the tread and inside of the new HTLR is shown on top, while a well-worn non-TLR version is shown below (which had actually been run tubeless with sealant...shhhh...don't tell anyone ;-)<br />
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Well, that got me curious, so I poked around the Challenge website a bit and found some things out. Apparently, when one of their tires is listed as having a single "PPS", that layer is installed BETWEEN the tread and the casing layer. When a tire is designated as "2xPPS", that means an additional layer is installed on the inside of the casing, so that it would be between the casing and the tube. Aaah...so, that must mean that despite the sidewall labeling being marked as "2xPPS" on the new tire, they must have eliminated at least the inside layer.<br />
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With a bit more digging on the Challenge site, I then came across this graphic, and I think it explains what's going on:<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiAYHPj3DnLu9TcsXMM5t6G3YE4UXYX-7Ui-mM5VfSnjzO59T89SlHV1nB4KnfNvzulknofotAS7TPqhZ9RhlQoVinJW6S4-6KnOql7iKckDhodQ-BtdoC1LokGchSxv5aaupBi6En7zc4/s1600/Challenge+PPS.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="350" data-original-width="392" height="356" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiAYHPj3DnLu9TcsXMM5t6G3YE4UXYX-7Ui-mM5VfSnjzO59T89SlHV1nB4KnfNvzulknofotAS7TPqhZ9RhlQoVinJW6S4-6KnOql7iKckDhodQ-BtdoC1LokGchSxv5aaupBi6En7zc4/s400/Challenge+PPS.png" width="400" /></a></div>
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I think I see what's going on...the original HTLR tires must have been mis-labeled...OK, that makes sense.</div>
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Anyway...finally, here's how these 2 tires fared in the roller tests (again, full spreadsheet is located at the link to the right, or <a href="https://docs.google.com/spreadsheets/d/1TP2UiAIyAbK7iR2X0mlGWWB7aJkbOecfrCmimqwcdGk/edit?usp=sharing" target="_blank">here</a>):<br />
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<u>TIRE</u> <u>CRR</u> <u>POWER (pair @30kph)</u><br />
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<ul><a href="https://www.blogger.com/blogger.g?blogID=6080071290235905056" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a><a href="https://www.blogger.com/blogger.g?blogID=6080071290235905056" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a><a href="https://www.blogger.com/blogger.g?blogID=6080071290235905056" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a><a href="https://www.blogger.com/blogger.g?blogID=6080071290235905056" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a>
<li><span style="font-family: "arial" , "helvetica" , sans-serif;">Challenge Gravel Grinder Pro HTLR 700x36c .0041 29W</span></li>
<li><span style="font-family: "arial" , "helvetica" , sans-serif;">Continental Terra Trail 700x40c .0056 39W</span></li>
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<span style="font-family: arial, helvetica, sans-serif;">So, the Challenge GGPro HTLR tire basically rolled identically to the non-TLR GGPro. Seems like any additional rolling resistance from the sealing layers was offset by the elimination of one of the 2 PPS layers. That's a fair trade...</span></div>
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<span style="font-family: arial, helvetica, sans-serif;">On the other hand, I was slightly disappointed in the Terra Trail performance. I was hoping that the only change was to the outer tread blocks, but I have a feeling additional rubber was also added on the sidewalls. I was hoping it would roll somewhere in a slot ~halfway between the difference in what they actually rolled, but alas, that was not to be. To be fair though, I'm currently using that tire as a front, and I really appreciate the extra grip in loose dirt from the larger side knobs...it's just quite "buzzy" on pavement.</span></div>
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<span style="font-family: arial, helvetica, sans-serif;">I still wish both of these tires were actually slightly wider...more like 42-43mm measured, rather than the 36mm measured for the Challenge, and 39mm measured for the Terra Trail</span></div>
Tom Anhalthttp://www.blogger.com/profile/08175472546482777614noreply@blogger.com11tag:blogger.com,1999:blog-6080071290235905056.post-51400738572781074582020-03-15T18:30:00.002-07:002020-07-13T16:52:53.481-07:00Tubeless Tire Plugging<div class="separator" style="clear: both; text-align: center;">
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One of the things that has, in my opinion, slowed the adoption of tubeless tire technology in road bicycles has been the "hassle factor" of dealing with punctures that can't be effectively sealed while riding. The sealant inside the tires can typically do a great job of handling small punctures, such as those from "goat heads" or wires from radial car tires, but it's been my experience that for most punctures or cuts that are larger than ~1mm, the sealant just can't do the job without intervention. This is most likely due to the higher pressures and lower tire air volume in this application, as compared to other bicycle types such as MTBs, where tubeless technology is the default at present.<br />
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When I first started sampling road tubeless technology, the "intervention" mentioned above meant putting a spare inner tube inside the tire, with all of the mess (sealant) and hassle (tight tire beads) that entails. In fact, I was pretty discouraged in my first forays into running a tubeless road bike tire after 2 out of the first 3 rides on one resulted in cuts too big to seal and a struggle to install a tube. I really didn't "get it", especially when the performance/reliability of regular tires with tubes (latex, of course) inside them was quite good for me.<br />
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Anyway, sometime after that "experiment" with road tubeless, and about the time I started thinking about putting together an "all-road" bike, I came across this internet thread:<br />
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<a href="https://forums.mtbr.com/arizona/tubeless-repair-how-692120.html">https://forums.mtbr.com/arizona/tubeless-repair-how-692120.html</a><br />
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In it, you'll see a discussion of a technique that some mountain-bikers had adopted of carrying along small swatches of cotton cut from old t-shirts to use as a plug of sorts for large punctures and cuts which tubeless sealant couldn't solve alone. The technique involved carrying along a short piece of wheel spoke to "poke" the cotton swatch into the hole to allow the sealant to have something to congeal on. At one point in the thread, someone mentions using cotton string...and that got me thinking.<br />
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I had seen a small tire plug kit that is produced by Genuine Innovations that consists of a miniaturized version of a tire plug tool used for automotive/motorcycle use. This plug tool basically looks like a screwdriver handle and shaft, with the tip being a small, 2 prong fork. The idea is that when a puncture happens, you load the fork with one of the "strips of bacon" (short lengths of cord covered with a somewhat sticky rubber substance). You then insert the tool into the hole in the tire, give the tool a 90-180 degree twist (so that a small loop is formed inside the tire) and then pulled straight out. Knowing all of this...and then seeing the use of cotton with tire sealant, I began to wonder if simple lengths of cotton butcher's cord (like used for tying up roasts and the like for cooking) would work?<br />
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Well...it turns out it works, and quite well! In fact, this is now my first line of defense in dealing with a tubeless tire puncture that won't self-seal. I save the supplied "strips of bacon" for cases where either the sealant is dried out, or the conditions are too wet for the plain cotton thread to work.<br />
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<span style="background-color: #f4f8fb; box-sizing: border-box; font-family: "arial"; font-size: 14px;">Here's what a cotton butcher's cord plug ends up looking like inside the tire when working with Orange Seal:</span><span style="background-color: #f4f8fb; font-family: "open sans"; font-size: 14px;"></span><br />
<img src="https://i.imgur.com/djJVNEf.jpg" style="background-color: #f4f8fb; box-sizing: border-box; font-family: "Open Sans"; font-size: 14px; height: auto; max-width: 100%;" width="650" /><span style="background-color: #f4f8fb; font-family: "open sans"; font-size: 14px;"></span><br />
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<span style="background-color: #f4f8fb; box-sizing: border-box; font-family: "arial"; font-size: 14px;">Here's the sequence of how it got to that point:</span><span style="background-color: #f4f8fb; font-family: "open sans"; font-size: 14px;"></span><br />
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<span style="background-color: #f4f8fb; box-sizing: border-box; font-family: "arial"; font-size: 14px;">- Insert pre-cut cotton butcher's cord (or "bacon" strip) in tool. With cotton, this can be done in advance and the tool stored that way:</span><span style="background-color: #f4f8fb; font-family: "open sans"; font-size: 14px;"></span><br />
<span style="background-color: #f4f8fb; box-sizing: border-box; font-family: "arial"; font-size: 14px;"></span><img src="https://i.imgur.com/ypbUje0.jpg" style="background-color: #f4f8fb; box-sizing: border-box; font-family: "Open Sans"; font-size: 14px; height: auto; max-width: 100%;" width="650" /><span style="background-color: #f4f8fb; font-family: "open sans"; font-size: 14px;"></span><br />
<span style="background-color: #f4f8fb; box-sizing: border-box; font-family: "arial"; font-size: 14px;"><img src="https://i.imgur.com/Ahum8Oi.jpg" style="box-sizing: border-box; height: auto; max-width: 100%;" width="650" /></span><span style="background-color: #f4f8fb; font-family: "open sans"; font-size: 14px;"></span><br />
<span style="background-color: #f4f8fb; box-sizing: border-box; font-family: "arial"; font-size: 14px;"><br /></span>
<span style="background-color: #f4f8fb; box-sizing: border-box; font-family: "arial"; font-size: 14px;">- Insert tool into puncture hole</span><span style="background-color: #f4f8fb; font-family: "open sans"; font-size: 14px;"></span><br />
<img src="https://i.imgur.com/cftfwK0.jpg" style="background-color: #f4f8fb; box-sizing: border-box; font-family: "Open Sans"; font-size: 14px; height: auto; max-width: 100%;" width="650" /><span style="background-color: #f4f8fb; font-family: "open sans"; font-size: 14px;"></span><br />
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<span style="background-color: #f4f8fb; box-sizing: border-box; font-family: "arial"; font-size: 14px;">- Twist tool ~90-180 degrees about the shaft and remove by pulling it straight out of tire</span><span style="background-color: #f4f8fb; font-family: "open sans"; font-size: 14px;"></span><br />
<a href="https://i.imgur.com/18EwSoA.jpg" style="background-color: #f4f8fb; box-sizing: border-box; color: #0b4fa0; font-family: "Open Sans"; font-size: 14px; outline: 0px; text-decoration-line: none;" target="_blank" title="Click to view full sized image"><img src="https://i.imgur.com/18EwSoA.jpg" style="box-sizing: border-box; height: auto; max-width: 100%;" width="650" /></a><span style="background-color: #f4f8fb; font-family: "open sans"; font-size: 14px;"></span><br />
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<span style="background-color: #f4f8fb; box-sizing: border-box; font-family: "arial"; font-size: 14px;">- Trim excess cord with pocket knife (I have a tiny promotional knife I keep in the tool kit) being careful not to pull excessively on the cords. I've heard of other folks packing a mini nail clipper for the same purpose. You can see how quickly the cord soaks up and is "infused" by the sealant. That eventually dries to create the "plug".</span><span style="background-color: #f4f8fb; font-family: "open sans"; font-size: 14px;"></span><br />
<a href="https://i.imgur.com/BRHk74x.jpg" style="background-color: #f4f8fb; box-sizing: border-box; color: #0b4fa0; font-family: "Open Sans"; font-size: 14px; outline: 0px; text-decoration-line: none;" target="_blank" title="Click to view full sized image"><img src="https://i.imgur.com/BRHk74x.jpg" style="box-sizing: border-box; height: auto; max-width: 100%;" width="650" /></a><span style="background-color: #f4f8fb; font-family: "open sans"; font-size: 14px;"></span><br />
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<span style="background-color: #f4f8fb; box-sizing: border-box; font-family: "arial"; font-size: 14px;">- Here's what it looks like immediately after trimming and wiping excess sealant</span><span style="background-color: #f4f8fb; font-family: "open sans"; font-size: 14px;"></span><br />
<a href="https://i.imgur.com/yJaHLqj.jpg" style="background-color: #f4f8fb; box-sizing: border-box; color: #0b4fa0; font-family: "Open Sans"; font-size: 14px; outline: 0px; text-decoration-line: none;" target="_blank" title="Click to view full sized image"><img src="https://i.imgur.com/yJaHLqj.jpg" style="box-sizing: border-box; height: auto; max-width: 100%;" width="650" /></a><span style="background-color: #f4f8fb; font-family: "open sans"; font-size: 14px;"></span><br />
<span style="background-color: #f4f8fb; box-sizing: border-box; font-family: "arial"; font-size: 14px;"><br style="box-sizing: border-box;" /></span><span style="background-color: #f4f8fb; font-family: "open sans"; font-size: 14px;"></span>
<span style="background-color: #f4f8fb; box-sizing: border-box; font-family: "arial"; font-size: 14px;">- Here's what it looks like after a couple hundred miles.</span><span style="background-color: #f4f8fb; font-family: "open sans"; font-size: 14px;"></span><br />
<a href="https://i.imgur.com/uap9dM8.jpg" style="background-color: #f4f8fb; box-sizing: border-box; color: #0b4fa0; font-family: "Open Sans"; font-size: 14px; outline: 0px; text-decoration-line: none;" target="_blank" title="Click to view full sized image"><img src="https://i.imgur.com/uap9dM8.jpg" style="box-sizing: border-box; height: auto; max-width: 100%;" width="650" /></a><span style="background-color: #f4f8fb; font-family: "open sans"; font-size: 14px;"></span><br />
<span style="background-color: #f4f8fb; box-sizing: border-box; font-family: "arial"; font-size: 14px;"><br /></span>
<span style="background-color: #f4f8fb; box-sizing: border-box; font-family: "arial"; font-size: 14px;">So...I'm sure some are wondering: Why not just use something like the Dynaplug kit?</span><br />
<span style="background-color: #f4f8fb; box-sizing: border-box; font-family: "arial"; font-size: 14px;"><br /></span>
<span style="background-color: #f4f8fb; box-sizing: border-box; font-family: "arial"; font-size: 14px;">I guess I just find the Dynaplug thing to be a bit "excessive"...especially at ~10X the initial cost, and then even more so for recurring...</span><br />
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<a href="https://images-na.ssl-images-amazon.com/images/I/51AgHpmlL8L.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="320" src="https://images-na.ssl-images-amazon.com/images/I/51AgHpmlL8L.jpg" style="box-sizing: border-box; font-family: "Open Sans"; height: auto; max-width: 100%;" width="320" /></a></div>
<span style="background-color: #f4f8fb; box-sizing: border-box; font-family: "arial"; font-size: 14px;"><br /></span>
<span style="background-color: #f4f8fb; box-sizing: border-box; font-size: 14px;"><span style="font-family: "arial" , "helvetica" , sans-serif;">There are kits out there that are equally as effective as the Dynaplug (if not more so, with the ability to insert multiple plug strips if needed) for much less money. For example, here's a newer kit from Genuine Innovations that's only $15:</span><br style="box-sizing: border-box; font-family: "Open Sans";" /><span style="font-family: "arial";"></span><br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><span style="font-family: "open sans";">The replacement "bacon strips" are also very inexpensive...or, you can go even less expensive by merely buying a lifetime supply of cotton butcher's cord (i.e. a single roll) and using those with the Genuine Innovations tool.</span></span><br />
<span style="background-color: #f4f8fb; box-sizing: border-box; font-size: 14px;"><span style="font-family: "open sans";"><br /></span></span>
<span style="background-color: #f4f8fb; box-sizing: border-box; font-size: 14px;"><span style="font-family: "open sans";">Here's a few views of the kits I have in the tool pack on a couple of bikes:</span></span><br />
<span style="background-color: #f4f8fb; box-sizing: border-box; font-size: 14px;"><span style="font-family: "open sans";"><br /></span></span>
<span style="background-color: #f4f8fb; box-sizing: border-box; font-size: 14px;"><span style="font-family: "open sans";">The first one is all wrapped up in a small plastic baggie and inserted into a pocket of my seat roll. The 2nd one lives in the top tube pack on my all-road bike.</span></span><br />
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<span style="background-color: #f4f8fb; box-sizing: border-box; font-size: 14px;"><span style="font-family: "open sans";"><br /></span></span><span style="background-color: #f4f8fb; box-sizing: border-box; font-size: 14px;"><span style="font-family: "open sans";"><br /></span></span><br />
<span style="background-color: #f4f8fb; box-sizing: border-box; font-size: 14px;"><span style="font-family: "open sans";"><br /></span></span><span style="background-color: #f4f8fb; box-sizing: border-box; font-size: 14px;"><span style="font-family: "open sans";">Anyhow...that's how I handle those punctures now. It's definitely quicker than swapping in a tube.</span></span>
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<span style="background-color: #f4f8fb; box-sizing: border-box; font-size: 14px;"><span style="font-family: "open sans";"><br /></span></span>Tom Anhalthttp://www.blogger.com/profile/08175472546482777614noreply@blogger.com9tag:blogger.com,1999:blog-6080071290235905056.post-56535843613011613232020-02-16T15:41:00.001-08:002021-04-01T17:44:49.425-07:00Time to Share Some "Gravel Fun"<div class="separator" style="clear: both; text-align: center;">
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<b><i>*edit 18Feb2020: There's a late-breaking addition to the list after I recently completed a test on the new Continental Terra Speed. See the list below and in the spreadsheet</i></b><br />
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OK...yeah, I know...it's been awhile since I wrote something here :-)<br />
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But, it's a new year (relatively speaking) and I've got some stuff I'd like to finally share. So, below is my first go at presenting hard surface rolling resistance data on tires intended for mixed-surface riding, A.K.A "gravel riding". I'm sure I'll be opening myself up to criticism from certain corners of the interwebs for looking at this, but I'll discuss below some of my reasoning on the subject and try to put the information into the proper (usable) context.<br />
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So, without further ado, here's a quick list of what I've tested so far, in descending order of Crr (full spreadsheet is located at the link to the right, or <a href="https://docs.google.com/spreadsheets/d/1TP2UiAIyAbK7iR2X0mlGWWB7aJkbOecfrCmimqwcdGk/edit?usp=sharing" target="_blank">here</a>):<br />
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<u>TIRE</u> <u>CRR</u> <u>POWER (pair @30kph)</u><br />
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<a href="https://www.blogger.com/blogger.g?blogID=6080071290235905056" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a><a href="https://www.blogger.com/blogger.g?blogID=6080071290235905056" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a><a href="https://www.blogger.com/blogger.g?blogID=6080071290235905056" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a><a href="https://www.blogger.com/blogger.g?blogID=6080071290235905056" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a>
<li><span face=""arial" , "helvetica" , sans-serif">Continental GP5000S 700x23c .0029 20W</span></li>
<li><span face=""arial" , "helvetica" , sans-serif">Specialized Turbo Cotton 700x28c .0031 21W</span></li>
<li><span face=""arial" , "helvetica" , sans-serif">Continental GP4000S 700x23c (control) .0035 25W</span></li>
<li><span face=""arial" , "helvetica" , sans-serif">Challenge Strada Bianca Pro 700x30c .0036 25W</span></li>
<li><span face=""arial" , "helvetica" , sans-serif">Compass Snoqualmie Pass EL 700x44c .0036 25W</span></li>
<li><span face=""arial" , "helvetica" , sans-serif">Challenge Strada Bianca Pro 700x36c .0038 27W</span></li>
<li><span face=""arial" , "helvetica" , sans-serif">Challenge Gravel Grinder Pro 700x36c .0041 29W</span></li>
<li><span face=""arial" , "helvetica" , sans-serif"><i>Continental Terra Speed 700x40C .0043 30W*</i></span></li>
<li><span face=""arial" , "helvetica" , sans-serif">Compass Snoqualmie Pass 700x44c .0043 30W</span></li>
<li><span face=""arial" , "helvetica" , sans-serif">Panaracer Pari Moto 650Bx48c .0047 33W</span></li>
<li><span face=""arial" , "helvetica" , sans-serif">Challenge Gravel Grinder Race 700x42c .0047 33W</span></li>
<li><span face=""arial" , "helvetica" , sans-serif">Compass Bon Jon Pass 700x35c .0048 33W </span></li>
<li><span face=""arial" , "helvetica" , sans-serif">Challenge Gravel Grinder TLR 700x42c .0050 34W</span></li>
<li><span face=""arial" , "helvetica" , sans-serif">Panaracer Gravel King SK 700x32c .0051 35W</span></li>
<li><span face=""arial" , "helvetica" , sans-serif">Challenge Gravel Grinder TLR 700x38c .0051 35W</span></li>
<li><span face=""arial" , "helvetica" , sans-serif">Compass Steilacoom EL 700x38c .0056 39W </span></li>
<li><span face=""arial" , "helvetica" , sans-serif">WTB Byway 650Bx47 .0056 39W</span></li>
<li><span face=""arial" , "helvetica" , sans-serif">Challenge Gravel Grinder Race 700x38c .0057 40W</span></li>
<li><span face=""arial" , "helvetica" , sans-serif">Vittoria Terreno Dry 700x40c .0057 40W</span></li>
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<u>Explanation:</u></div>
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Before diving into the actual results, it would be good to review a few notes about some of the test conditions and how the results are reported:<br />
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<li>The tires listed above (unless otherwise noted) have been tested at a pressure predicted to correspond with a tire "drop" (i.e. deflection under load) of 15% of the inflated casing height. There will be more on how that pressure is calculated below. The reason for doing so is that the tires in this category can vary in size by quite a bit, and it makes sense to compare their performance in a more "apples to apples" condition than with a fixed pressure (as I have done previously with road tires of similar size to each other).</li>
<li>The power for a pair of tires is shown compared at 30kph, unlike the previous reporting for road tires at 40kph. This is to account for the generally lower average speeds encountered in mixed-surface riding. The spreadsheet reports values for 20, 30, and 40kph instead of the road spreadsheet reporting of 30, 40, and 50kph</li>
<li>The top 3 tires listed are basically road tires. The Continental GP5000, although a 23C tire is listed mostly because I haven't shown a result for that yet (and some information linked to below indicates that the performance of the larger sizes is basically identical when run at Berto pressure). The GP4000S is just shown as a "control" and comparison to my previous road only results (still linked at the right). Lastly, the 28C Specialized Turbo Cotton is also another road tire I haven't shown results for in the past...but, in this case, I consider it to be the first of tires I would consider for "light gravel" use (and have used it as such). On rims of 20-21mm internal width, those tires measure nearly 29mm wide.</li>
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<u>Discussion of Berto Pressure calculations:</u></div>
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Quite a long time ago, after discussing the subject with tire engineers, Frank Berto took on the task of measuring a range of tire sizes to determine the pressure required to result in a 15% deflection of the tire casing for a given load. The assumption was that this deflection point resulted in a consistent performance for a given tire size and load...and, if anything, was at least a good "starting point" for determining a preferred pressure. The results of those tests are shown in the chart by Berto above.<br /><br />
Because I wanted to use the charts for a wider range of tires and for sizes in between the shown lines for tire sizes, I decided to see if I could come up with a "universal" Berto pressure equation. To do so, I calculated the slope and intercept dependencies on tire size and wheel load. This resulted in a "pressure intercept" and "pressure slope" for each tire size curve. I then plotted these intercepts and slopes versus tire size in order to come up with a curve fit for each (and they were surprisingly linear). This exercise resulted in a "universal equation" to solve for pressure for any size and load. Now it's not necessarily predictive of actual pressures one would run (since that can be highly surface dependent) but it's a way to "normalize" for comparison purposes. That equation is embedded in the spreadsheet.<br />
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As an example, BicycleRollingResistance.com did a comparison of 4 different sizes of the Contintental GP5000 tires: <a href="https://www.bicyclerollingresistance.com/specials/grand-prix-5000-comparison">https://www.bicyclerollingresistance.com/specials/grand-prix-5000-comparison</a> , and in an interesting comparison there, the rolling resistance measured for all 4 sizes was within 1W when "normalized" to a measured 15% tire deflection. Perhaps ol' Frank was on to something ;-)<br />
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<img height="407" src="https://forum.slowtwitch.com/forum/?do=post_attachment;postatt_id=25384" width="640" /></div><br />
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Anyway...I think I'll just throw this info out there for now to hopefully stimulate some discussion, and will probably go into further depth on the subject in future blog posts (I promise!)</div>
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Tom Anhalthttp://www.blogger.com/profile/08175472546482777614noreply@blogger.com18tag:blogger.com,1999:blog-6080071290235905056.post-61804557473146218742017-03-19T15:58:00.002-07:002017-03-19T15:58:37.047-07:00Holy Moly...Vittoria Corsa Speed TLR<div class="separator" style="clear: both; text-align: center;">
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<span style="font-family: Arial, Helvetica, sans-serif;">Since their introduction, there's been a lot of "buzz" about the newest Vittoria tires which incorporate Graphene into their tread compounds. In particular, the Corsa Speed model has been touted in various locations as the fastest tire. Despite being only offered in one size (23C), it's intriguing in that it's the first "Tubeless Ready" tire on the market that utilizes the "open tubular" type of construction, with a flexible cotton-casing and a separately glued-on tread. I finally acquired a set of the Corsa Speed tires and put them to the rollers. So...are the fast? The answer to that is an emphatic "YES!"</span><br />
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<span style="font-family: Times, Times New Roman, serif;">To cut to the chase...I tested the Corsa Speed in 3 ways:</span></span><br />
<ol>
<li><span style="font-family: Arial, Helvetica, sans-serif;">First, on my standard test wheel (Mavic Open Pro) with a latex tube inside, 120psi.</span></li>
<li><span style="font-family: Arial, Helvetica, sans-serif;">Next, on a Jet6+ wheel with a latex tube, 100psi</span></li>
<li><span style="font-family: Arial, Helvetica, sans-serif;">Lastly, on the Jet6+ wheel set up tubeless, with 40ml of Orange Seal.</span></li>
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<span style="font-family: Arial, Helvetica, sans-serif;">As I've described in the past, I've found that the 120psi results on the Open Pro rim match the 100psi results on the Jet6+ rim, and this way I could confirm that once again while having a result (on the Open Pro) that can be more directly compared to the majority of tire test conditions in my spreadsheet. Here's the results:</span></div>
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<span style="font-family: Arial, Helvetica, sans-serif;">Vittoria Corsa Speed TLR 23C, latex tube, Open Pro (120 psi) = .0025, 23W for pair @ 40 kph</span></div>
<span style="font-family: Arial, Helvetica, sans-serif;">Vittoria Corsa Speed TLR 23C, latex tube, Hed Jet6+ (100 psi) = .0025, 24W for pair @ 40 kph</span><br />
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<span style="font-family: Arial, Helvetica, sans-serif;">Vittoria Corsa Speed TLR 23C, tubeless, Hed Jet6+ (100 psi) = .0025, 24W for pair @ 40 kph</span></div>
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<span style="color: #222222; font-family: Times, Times New Roman, serif;"><span style="background-color: white; font-family: Arial, Helvetica, sans-serif;">As you can see, the results are basically identical, with rounding differences in the 5th decimal place of the Crr estimate accounting for the 23W vs. 24W values in the estimated power for a pair of tires.</span></span><br />
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<span style="color: #222222; font-family: Times, Times New Roman, serif;"><span style="background-color: white;">The Corsa Speeds are the new champs on my list...and not by a small amount, but by a fairly significant jump! The next closest new tires are a full 3W behind for a pair at 40kph.</span></span></span><br />
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<span style="color: #222222; font-family: Times, Times New Roman, serif;"><span style="background-color: white;">As I described above, the Corsa Speeds are built in a traditional Vittoria Corsa manner, with a cotton-based casing and a separate tread. One of the things that's different about this particular tire is that there is a grey, flexible coating (feels to be a latex-based coating to the hand) not only on the sidewalls of the tire, but also on the majority of the inner surface as well. This most likely is done to help enhance the air sealing capabilities of the tire...and it seems that this particular construction for tubeless road tires might require more sealant being used on initial installation. I found that the air loss for the tire was unacceptable until I had inserted ~50-60ml of sealant. After that, the tire has held air perfectly fine.</span></span></span><br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjZajwNZ5RFl74tzhmK6QhRH508nMu4ICw3kVsHtGODwlRRdz5CFzF5zPuatLVqc4guVwc75ue1PzRKGJ4_MU-OVaDCLdyj9rSZ2OMfmRjTxwRq17zxsFITvs0AZpmkA0t2Op49rfR09iY/s1600/IMG_2215%255B1%255D.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><span style="font-family: Arial, Helvetica, sans-serif;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjZajwNZ5RFl74tzhmK6QhRH508nMu4ICw3kVsHtGODwlRRdz5CFzF5zPuatLVqc4guVwc75ue1PzRKGJ4_MU-OVaDCLdyj9rSZ2OMfmRjTxwRq17zxsFITvs0AZpmkA0t2Op49rfR09iY/s320/IMG_2215%255B1%255D.JPG" width="320" /></span></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span style="font-family: Arial, Helvetica, sans-serif; font-size: small;">Coating inside casing. Appears to be same as sidewall coating</span></td></tr>
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<span style="color: #222222; font-family: Times, Times New Roman, serif;"><span style="background-color: white;">This is a thin tire, and I'm not sure if it has any type of puncture breaker under the tread...and so most would be concerned about it's durability. To test that out, I've been running it as a rear tire on my road bike and have currently ~500 miles in "not so pristine" road conditions. We've had a good amount of rain this winter in Southern California, and the road shoulders are littered with debris right now. So far the only mishap has been a small staple that was picked up by the tire. I noticed the staple prior to a ride, and hadn't spun the tire before pulling it out. That was a mistake in that it took me a bit to get the sealant to work on the very small hole...but, eventually it held and the sealant has formed a nice plug in that area that is holding just fine.</span></span></span><br />
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<span style="color: #222222; font-family: Times, Times New Roman, serif;"><span style="background-color: white;">So far so good...I'm really liking this tire. I've also recently discovered a tubeless repair technique that I think will dramatically alter the "hassle factor" of dealing with a hole large enough for sealant to have a hard time plugging. I'll be going over that technique in a future blog post.</span></span></span><br />
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<span style="color: #222222; font-family: Times, Times New Roman, serif;"><span style="background-color: white;">There you go...a new "top dog" has been confirmed.</span></span></span>Tom Anhalthttp://www.blogger.com/profile/08175472546482777614noreply@blogger.com40tag:blogger.com,1999:blog-6080071290235905056.post-3827859480290378042017-03-06T21:31:00.000-08:002017-03-07T16:37:55.524-08:00Stinner Aero Camino - Hot Rod American Steel - Part I<i>Ever since my <a href="http://bikeblather.blogspot.com/2015/10/win-tunnel-playtime-part-2.html" target="_blank">"Win Tunnel Playtime"</a> series of posts on this blog, I've quite often been asked about the details of my personal bike shown there. Here's the story of how that bike came about and some insight into its design.</i><br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg8P1dbyF2qJV0QeP8R20-HRBD4oq4vzfCB20r5lijkfYSbq4tlarmr5B2G3I6R1SdXz1YDmEuqGLmAUQiXlGNE6-iNLVn8IpvZxEg3BODvCVPZQFsA3jRu5v04pRzeETh7QtkT_enwJCc/s1600/2016-03-26+10.14.38.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg8P1dbyF2qJV0QeP8R20-HRBD4oq4vzfCB20r5lijkfYSbq4tlarmr5B2G3I6R1SdXz1YDmEuqGLmAUQiXlGNE6-iNLVn8IpvZxEg3BODvCVPZQFsA3jRu5v04pRzeETh7QtkT_enwJCc/s400/2016-03-26+10.14.38.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Stinner Aero Camino: Road Art</td></tr>
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It was time to go to work. As I opened the door to the garage from my house, I saw the exterior roll-up door was half open. My heart went into my throat. Did I accidentally leave it open? Did I not watch it descend all the way when I closed it yesterday?<br />
<br />
I quickly scanned around the garage to see if anything was missing and immediately saw that my Cervelo S5 road bike was gone. My stomach turned into knots. How could I be so careless? I looked around some more and realized that also missing was my older aluminum Cervelo Soloist, along with the nearly identical model (same year, 2002) that was my son's first road bike. Shit. How did this happen?<br />
<br />
As soon as I hit the garage door button to fully open the door and it didn't move, I realized exactly what had happened. Thieves had cracked one of the garage door windows at the top of the door and pulled the door emergency release cord. Once the door was released from the track, that allowed them to easily roll up the door. After seeing that, I could kick myself...how could I have not realized that it was so easy to break into my garage? Great, now I get to have the "fun" of dealing with a police report and my homeowner's insurance...<br />
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One consolation to this event was that the dirtbags didn't completely clear me out of bikes. Our MTBs and my old commuter bike were still there, along with my first "real" road bike as an adult: a 1986 Bianchi Sport SX that I had originally bought brand new. It looked like I was going to be doing my road rides on "Violet" (so named due to the snazzy factory semi-metallic purple paint - officially called "Flaming Violet") for the near future. Violet is a Japanese built Bianchi: Tange steel tubed frameset, complete with downtube shifters. I figured that since she was my only road bike available, I'd put the best wheels and tires I had remaining on Violet, just to minimize any performance disadvantage of using a 30 year old bike on my road rides. I had a set of Zipp 101s I could use, along with a pair of Specialized Turbo Cotton 24C tires. With latex tubes inside, Violet was getting a new set of dancing shoes.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhqDeinp2yK4MaaSREp7T9grlZBvO11eYRRwTw5YoXLfX7hUKrwb9CQmbCfD7iH8nXv98LqfuXw5TNcTo3fdPN7Kr8fTdQBibdFcTk3Hunxk9qfYg8QN93TJjG4PqVAEhASOXEC7URn-Vs/s1600/2016-04-24+18.44.19.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="476" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhqDeinp2yK4MaaSREp7T9grlZBvO11eYRRwTw5YoXLfX7hUKrwb9CQmbCfD7iH8nXv98LqfuXw5TNcTo3fdPN7Kr8fTdQBibdFcTk3Hunxk9qfYg8QN93TJjG4PqVAEhASOXEC7URn-Vs/s640/2016-04-24+18.44.19.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">1986 Bianchi Sport SX "Violet" - After surviving the 2016 Belgian Waffle Ride</td></tr>
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A funny thing happened as I started riding around with Violet and her new shoes...I began to realize that aside from the weight (~22 lbs), this 30 year old bike wasn't slow. I was easily able to "hang" on the fast group rides, and it was only when the roads tilted up to a great degree did we slow down (relatively speaking)...but that could have been just as much the fault of my own mass as Violet's. I had originally thought that I was going to replace the S5 with a brand new model (the 2nd generation of that bike had just been released)...but now I started thinking about other options. One of those options was a custom frame built by a local framebuilder who had been making quite a name for himself after being awarded the <a href="http://2012.handmadebicycleshow.com/2012-news/2012/03/07/2012-nahbs-awards-winners/" target="_blank">NAHBS "Rookie of the Year" award</a> in 2012: Aaron Stinner, of <a href="http://www.stinnerframeworks.com/" target="_blank">Stinner Frameworks</a>.<br />
<br />
Thus began the project that became: The Stinner Aero Camino custom prototype.<br />
<br />
Once I realized that a narrow-tubed steel bike could "hang" with modern equipment, I was really intrigued about taking that understanding to the limit. Knowing that aerodynamic drag is the largest impediment to bike movement at any speed above ~15kph (9.3mph), is it possible to configure a custom steel bike to have excellent aerodynamics? Can we do it in a package that's closer in weight to more modern road bikes? Sure, the largest aero drag impediment for a cyclist is the rider themselves...but, once you have that sorted, next up is the bike.<br />
<br />
I had known of Aaron since he was a high school kid living literally just down the block from me. I remember seeing him coast past my house at the end of his training rides. He's hard to miss; tall and lanky. I had been aware that he had eventually decided to become a custom framebuilder, and had also been pleased to see his hard work result in his 2012 NAHBS award. It was also tough to miss Aaron's work when I saw it locally and had been impressed by the detail and creativity. One day I was doing a group ride and began discussing some of my ideas with Aaron's business partner of the time, and he really like some of the ideas I was floating. He suggested I contact Aaron and we start talking about the collaboration. So I gave Aaron a shout and he suggested I swing by the shop on one of my off days and we'd go for a ride and talk bikes.<br />
<br />
It didn't take long on that ride to realize that both Aaron and I were on the same page about the geometry and features that make for a good all-around road bike. Interestingly enough, it sounded as if it might end up being a carbon-copy of the geometry of Violet, but in an updated form. I emphasized that I wanted the result to be as "clean" aerodynamically as possible, especially at the front of the bike. This meant using a "known good" aero fork (I was able to source a 1st Gen Cervelo S5 fork) with an inset headset, along with internal cable routing. I wanted the cabling from the bars to enter the frame behind the headset, and Aaron and I discussed various ways to accomplish that. I suggested that we offset the leading edge of the downtube at the bottom bracket to form a "fish mouth" that would allow the cables to exit, which is something I "stole" from the Cervelo aluminum Soloist frame design. I even suggested that we might want to extend the downtube past the BB a bit, and then mount the rear brake below the chainstays. The extension would tend to "fair" the brake, and the opening would make running the internal brake routing very easy. In fact, I could run full housing all the way to the brake from the bars.<br />
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The only thing left to decide on was the main frame tubes and the stays. I didn't want a round down tube, and was open to "flattening" a tube to ovalize it. We decided to both do some research on what types of tubes were available that might fit the purpose. Perhaps there were some decent aerodynamically shaped steel tubes? For the top tube, Aaron wanted a flattened area near the head tube so that there would be more room for the cable stops/entries. For the stays, I left the chainstays up to Aaron's discretion (he recommended Columbus Life Oval stays), but told him I really had my eyes on some of the True Temper Velo tear-drop shaped seat stays that I had seen on some Yamaguchi track and road bikes. And I wanted them to be "dropped", or attached at the seat tube below the top tube to seat tube junction. This would effectively elongate the teardrop section with respect to the air flow direction.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em; text-align: left;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEilIF7OwJygwqsnzpXp0KnAgzfa2D5csiIVPR5Xj4QtyGguDQ9ZdwCt3JklAv-SjS6gAlfLaLku04DjBtbM0oC-zem0R_mpUKNGfl0nX2Vm5-vvp73ILPfU9XymsMvZ-gUhOgjZBorMwfo/s1600/yamaguchi-silver-road-5.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="424" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEilIF7OwJygwqsnzpXp0KnAgzfa2D5csiIVPR5Xj4QtyGguDQ9ZdwCt3JklAv-SjS6gAlfLaLku04DjBtbM0oC-zem0R_mpUKNGfl0nX2Vm5-vvp73ILPfU9XymsMvZ-gUhOgjZBorMwfo/s640/yamaguchi-silver-road-5.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">True Temper Velo Seatstays on a Yamaguchi road bike</td></tr>
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The only round tubes on the bike were going to be the head tube and the seat tube, the latter of which was selected to hold a standard 27.2mm seat post.<br />
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As we contemplated flattening the one end of the top tube, Aaron suggested that maybe we should take a look at the Columbus Max bi-oval tube for this purpose. This tube is typically used as a downtube, and on each end it is slightly flattened, with both ends flattened in a direction 90 degrees from each other. When run as a downtube, the horizontally flattened end is usually attached to the BB, with the vertically flattened end welded to the head tube. For this project, the idea was to "flip it around" and use it as a top tube, with the horizontally flattened end at the head tube, and the vertically flattened end at the seat tube area. This did a couple things: First, it gave us the flat area just behind the head tube to use for cable entry, the width of the tube at the head tube junction better matched up with the width of the 44mm wide head tube needed for the inset headset, and lastly, the width of the tube at the seat post end also matched up nearly perfectly with the diameter of the seat tube. It was a total win-win-win. For aesthetic reasons, it was decided to make sure that the top tube wasn't completely horizontal on it's centerline, since the flaring of the tube on each end would then make it appear the tube sloped up as it went rearward...so, a slight downward slope to the seat tube it was going to be!<br />
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That left just what to do about the downtube. At this point Aaron suggested I look at the Columbus Life Aero tube shape, which is more of an "egg" shape than a true air foil. After recalling an <a href="http://www.slowtwitch.com/mainheadings/techctr/frametube.html" target="_blank">old aero bicycle tube</a> test by John Cobb, in which one of the "aero" tubes tested faster overall when reversed (i.e. pointy end forward), I told him I wanted to do some quick CFD (Computational Fluid Dynamics) runs on the tube shape and that I might ask him to put the tube in "backwards" if the calculations held up. I'm sure he thought I was totally crazy...<br />
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<span style="font-family: inherit;"><span style="background-color: white;">It was the look at downtube shapes in the Trek Speed Concept white paper that gave me the idea of how to do the analysis I did :-) </span><br /><br /><span style="background-color: white;">Since I was doing this at home, I only used Solidworks Flow Simulation. I happened to have a copy at the time due to some mentoring I was doing with the local HS robotics team, but only had a not-so-powerful laptop to run it on, so the analyses were justifiably very simplified. I took a tracing of the tube shape... </span></span><br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj1dauRi3qRoHKeclNAGDHm2DhkWINBvZNUoykZaEQ22ZPbA5-N1SCKoOZY9CNd82VaxV0wN4agAcK69Cc5xwKxkJXiYAcHSzKI0XbmsuxIgkXvXBtq9vkyw0BZ8sRgbWIQ25raMREhqdI/s1600/downtube_trace.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="246" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj1dauRi3qRoHKeclNAGDHm2DhkWINBvZNUoykZaEQ22ZPbA5-N1SCKoOZY9CNd82VaxV0wN4agAcK69Cc5xwKxkJXiYAcHSzKI0XbmsuxIgkXvXBtq9vkyw0BZ8sRgbWIQ25raMREhqdI/s320/downtube_trace.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Columbus Life Aero tube tracing</td></tr>
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<span style="font-family: inherit;"><br /></span>
<br />
...and then modeled the tube in Solidworks...<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg7HOCwftRc-7dljAIuQmJPdrylQmaoFlt9kgglbImGR3Hr7ef12do4Rvl3jsQAoBpKOXhfLVPJBPXh7azZoaAf7ZfWPfpSaNk2EKGLJWY9vOs9nXb5b-PQznl5lf5Ox5MPLRYiNQvOEHU/s1600/DownTube.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="315" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg7HOCwftRc-7dljAIuQmJPdrylQmaoFlt9kgglbImGR3Hr7ef12do4Rvl3jsQAoBpKOXhfLVPJBPXh7azZoaAf7ZfWPfpSaNk2EKGLJWY9vOs9nXb5b-PQznl5lf5Ox5MPLRYiNQvOEHU/s320/DownTube.JPG" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Solidworks Sketch Details</td></tr>
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<br />
...and took a 2D slice of the downtube (and bottle, when modeled) in the plane of the air flow with the downtube at the appropriate angle for the frame design. That obviously "elongated" the shapes in the flow plane. Here's an example of one of the analysis outputs: <br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgQhzLyc1eXwp3DFWBqs-udO01axZBtw-mLpuFbUBqxqTEGHgop9hKNOaNQ3x3vKe1c_mwniVstwNP2NMnFaNFesYWh1D2apPQJzYKdjsdyQnmGAn14doWjQi3_kL44X7Jx9xFOjJUmnSY/s1600/DT_flow.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="387" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgQhzLyc1eXwp3DFWBqs-udO01axZBtw-mLpuFbUBqxqTEGHgop9hKNOaNQ3x3vKe1c_mwniVstwNP2NMnFaNFesYWh1D2apPQJzYKdjsdyQnmGAn14doWjQi3_kL44X7Jx9xFOjJUmnSY/s400/DT_flow.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Solidworks Flow Simulation 2D Result Plot</td></tr>
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To attempt to get a gauge of the affect of bottle AND tube together over the entire length, I merely summed the respective per unit length drag for the bare tube and the tube plus bottle and plotted them out over yaw. Here are my estimates for the power required for just the downtube at an apparent wind speed of 40kph. The round tube entries are for the same Columbus tube, just without the aero shaping (i.e. pre-formed tube diameter).<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7yoypwM5Ni8g0I3qcL5nZGwBOrTrpQbLHwmZj8Y6ZTxzECo2ASt7pbVqcZad5BYnZZUTE4r34ALjeWgSPGHy_7M6r8Gny4GLppa5SaOk620WtSjsK0d3jDbAcE252JWZGuMvrJZMMfcg/s1600/Options_drag.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="414" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7yoypwM5Ni8g0I3qcL5nZGwBOrTrpQbLHwmZj8Y6ZTxzECo2ASt7pbVqcZad5BYnZZUTE4r34ALjeWgSPGHy_7M6r8Gny4GLppa5SaOk620WtSjsK0d3jDbAcE252JWZGuMvrJZMMfcg/s640/Options_drag.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Estimated Power for Downtube @ 40kph</td></tr>
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The "front" and "back" nomenclature refer to running the Columbus tube with the wide end forward ("as designed") or with it backwards. There are some neat takeaways from that exercise...one of them being that the Columbus DT run "backwards" and WITH a bottle is faster than the equivalent round tube with no bottle at all...and another being that above 5 deg yaw, the same configuration ("backwards", w/bottle) is as fast or faster than the same tube configuration with no bottle. This was looking good!<br />
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Of course, the major assumption in all of this is that this isolated look at the downtube is valid for the bike design. That's where the fact that Trek first undertook a similar approach in the SC development made me feel a bit better about using the results to decide on the tube orientation I wanted to try in the custom build. The downtube orientation was settled..."backwards" it is!<br />
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In the mean time, Aaron was working on the details of the rest of the frame design, and here's what he sent me for approval:<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgKTHHDjv-jLpWDRU-kP-HSNI4OLPJhm2rF0em-bdGtI5I4_Knud6RUlUhMmDG74ILeHo5D-D1zNmrQHKb3Ua6Ehm9ZHZzhcz7JvR_SmLKFfmc3DvD6HhCwjlIscEwGwWbkTDe2r8hXXjE/s1600/Stinner_Geo.JPG" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="492" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgKTHHDjv-jLpWDRU-kP-HSNI4OLPJhm2rF0em-bdGtI5I4_Knud6RUlUhMmDG74ILeHo5D-D1zNmrQHKb3Ua6Ehm9ZHZzhcz7JvR_SmLKFfmc3DvD6HhCwjlIscEwGwWbkTDe2r8hXXjE/s640/Stinner_Geo.JPG" width="640" /></a></div>
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<u>Here's how the frameset shook out material-wise:</u><br />
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<span style="font-family: inherit;"><span style="background-color: white;">-Fork is first generation Cervelo S5 model </span><br /><br /><span style="background-color: white;"><u>Tube specs is as follows: </u></span><br /><br /><span style="background-color: white;">-Head Tube: 44mm with Chris King Inset HS </span><br /><br /><span style="background-color: white;">-Down Tube: Columbus Life Aero 42mm (run narrow end forward, simple CFD suggested that was faster, especially with bottle). DT is offset at BB to allow cables to exit and partially "fair" rear brake below BB. </span><br /><br /><span style="background-color: white;">-Top Tube: Columbus MAX bi oval (oriented with horizontal flat at HT, and vertical flat at ST, both to match tube widths better at HT and ST junctions) </span><br /><br /><span style="background-color: white;">-Seat Tube: True Temper HVERST1 </span><br /><br /><span style="background-color: white;">-Chain Stays: Columbus life Oval </span><br /><br /><span style="background-color: white;">-Seat Stays: True Temper Velo Seat Stays (teardrop shape designed by Yamaguchi) </span><br /><br /><span style="background-color: white;">-Bottom Bracket: BSA threaded </span></span><br />
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After all of this was determined, I green-lighted the start of the actual construction. We were going to build a custom steel "aero road bike"!<br />
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The only thing left to do at this point was to come up with a name for it. Aaron has a range of customizable production models that are traditionally named after local roads and trails that have inspired the various designs...and I had been contemplating suggesting a name for this fully custom frame soon after we began talking about the build.<br />
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You see...his shop is on a small industrial strip near the Santa Barbara Airport. Obviously, many of the street and place names in Southern California are in Spanish. The street name of the shop address is "Aero Camino", which in English is translated as "Aero Road". I thought that "Aero Camino" would be a perfect name...and happily, Aaron did too.<br />
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Next up: The build, the paint, and the assembly.<br />
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<i>Aaron Stinner and his crew from <a href="http://www.stinnerframeworks.com/" target="_blank">Stinner Frameworks</a> are going to be displaying all of their awesome wares this coming weekend at the <a href="http://www.2017.handmadebicycleshow.com/" target="_blank">North American Handbuilt Bicycle Show (NAHBS)</a> in Salt Lake City (March 10-12, 2017). If you happen to be there, stop by and say "Hi" to them and make sure you check out the impressive range of "stock" and custom bikes. Especially check out the paintwork...or, more accurately, the artwork.</i><br />
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<br />Tom Anhalthttp://www.blogger.com/profile/08175472546482777614noreply@blogger.com14tag:blogger.com,1999:blog-6080071290235905056.post-82636037035585477662017-01-22T11:22:00.000-08:002017-01-23T13:03:58.038-08:00Getting Caught Up IIYeah...it's been awhile. Lots of things happening in the last year.<br />
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Anyway, It's time to get caught up. Although this tire rolling resistance data was published last spring after I did a collaboration with Jon and Chris of Flo Cycling (<a href="http://flocycling.blogspot.com/2016/06/flo-cycling-a2-wind-tunnel-tire-study.html" target="_blank">see report here</a>), I have been remiss in adding it to the spreadsheet linked to on the right side of this blog. These are tires I roller tested for the Flo tire aero study, models of which I had not already tested. Here are the additions from that testing:<br />
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<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; font-size: 13.2px;">Continental GP4000SII 25C = .0031, 28W for pair @ 40kph</span><br />
<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; font-size: 13.2px;">Continental GP Attack</span><span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; font-size: 13.2px;"> 22C = .0033, 31W for pair @ 40kph</span><br />
<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; font-size: 13.2px;">Continental GP4000SII 23C = .0034, 31W for pair @ 40kph</span><br />
<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; font-size: 13.2px;">Schwalbe One Tubeless 25C = .0037, 34W for pair @ 40kph</span><br />
<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; font-size: 13.2px;">Schwalbe One Tubeless 23C = .0041, 38W for pair @ 40kph</span><br />
<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; font-size: 13.2px;">Felt TTR1 </span><span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; font-size: 13.2px;">23C = .0048, 45W for pair @ 40kph</span><br />
<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; font-size: 13.2px;">Continental Gatorskin 25C = .0048, 45W for pair @ 40kph</span><br />
<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; font-size: 13.2px;">Continental Gatorskin 23C = .0052, 48W for pair @ 40kph</span><br />
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<span style="color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif;"><span style="background-color: white; font-size: 13.2px;">The interesting points in there for me are the confirmation that the GP4000SII rolls the same as the previous GP4000S, plus how poorly the Gatorskin models roll at 17-20W worse than the GP4000SII for a pair at 40kph. Wow.</span></span><br />
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<span style="color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif;"><span style="background-color: white; font-size: 13.2px;">Additionally, in August of 2016, I finally got around to testing a pair of tires that Eric Reid had sent me. One was a brand new model of the Continental Force tire (I had only previously tested a lightly used one) and also a Continental GP TT tire. The latter is a tire that hasn't had much test data on it, so it's something I really wanted to see. Here are those results:</span></span><br />
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<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; font-size: 13.2px;">Continental GP Force 24C = .0030, 27W for pair @ 40kph</span><br />
<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; font-size: 13.2px;">Continental GP TT 23C = .0028, 26W for pair @ 40kph</span><br />
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<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; font-size: 13.2px;">That result for the GP TT makes it the new "top dog" for brand new tires I've roller tested. One caveat on that tire though...it measures much larger (24.6mm) than it's rated 23C on my narrow Mavic Open Pro rim, or nearly 2mm wider than a Continental SuperSonic 23C (22.8mm) on the same rim, and is only .0001 lower Crr (~1W difference at 40kph for a pair, or what I consider "tied").</span><br />
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<span style="color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif;"><span style="background-color: white; font-size: 13.2px;">Finally, in October of last year, I roller tested a couple of other tires. One was a newer version of the Continental 20C SuperSonic. I was interested to see if, like some of Conti's other tires, it had gotten any faster since I had last tested that model in 2012. It did. Here are the results:</span></span><br />
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<span style="color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif;"><span style="background-color: white; font-size: 13.2px;">Continental SuperSonic 20C =</span></span><span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; font-size: 13.2px;"> </span><span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; font-size: 13.2px;">.0030, 28W for pair @ 40kph</span><br />
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<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; font-size: 13.2px;">That's a fairly significant change from the previous measurement of .0034 for that tire, and corresponds to an improvement of ~3W @ 40kph for a pair, and is just as fast as many tires of MUCH greater width.</span><br />
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<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; font-size: 13.2px;">The other tire I tested in October was the Specialized S-Works Turbo Tubeless 26C model. This tire was interesting to me because it had been getting some "buzz" about how it was a super-fast tubeless tire (most aren't up to this point).</span><br />
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<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; font-size: 13.2px;">In this case, I tested it both with a latex tube inside, and then also set up tubeless, with Orange Seal sealant inside (~20ml). Both tests measured nearly exactly the same (within less than .0001 Crr) with the result being:</span><br />
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<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; font-size: 13.2px;">Specialized S-Works Turbo Tubeless 26C = .0032, </span><span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; font-size: 13.2px;">30W for pair @ 40kph</span><br />
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<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; font-size: 13.2px;">Although that's relatively fast for a tubeless tire, it's not the world-beater it had been hyped to be...especially considering that it's mounted width on my Hed Jet+ wheel for that testing was nearly 30mm!</span><br />
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<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; font-size: 13.2px;">Anyway...good to be back at it, and I've got some other fun stuff (not so much tire related, hopefully) to be sharing with all of you shortly. Again, all of these updated entries are in the spreadsheet link in the upper right of this page.</span><br />
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<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; font-size: 13.2px;"><i style="color: black; font-family: "Times New Roman"; font-size: medium;">edit 23Jan2017: After roller testing a newer version of the Continental SuperSonic in 2016 as described above, I decided to use the newer value in calculating the total power for the H3/Conti 20C SS combination in the chart shown in my last "Win Tunnel Playtime" post. With those changes, the chart looks as follows, and it appears the old H3 has some pretty good speed in it still with that tire:</i></span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgHBqwA1mp8IyOmPERvAdfzAbeHLqydgf0JkPewORDLC4yeMQXZ9OWXuBufrqQz_aCnfRc0qiDEFCpS1X-CbCUV8ZbZyuiFUaNOIuA8MioC2EoHKyn1Ac7ZY10tce1DfIglgcLRDTRscEQ/s1600/Ttl_Pwr_2.JPG" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="464" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgHBqwA1mp8IyOmPERvAdfzAbeHLqydgf0JkPewORDLC4yeMQXZ9OWXuBufrqQz_aCnfRc0qiDEFCpS1X-CbCUV8ZbZyuiFUaNOIuA8MioC2EoHKyn1Ac7ZY10tce1DfIglgcLRDTRscEQ/s640/Ttl_Pwr_2.JPG" width="640" /></a></div>
<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; font-size: 13.2px;"><i style="color: black; font-family: "Times New Roman"; font-size: medium;"><br /></i></span>Tom Anhalthttp://www.blogger.com/profile/08175472546482777614noreply@blogger.com19tag:blogger.com,1999:blog-6080071290235905056.post-61887988296282056422016-03-06T15:48:00.000-08:002017-01-23T13:00:49.724-08:00Win Tunnel Playtime - Part 3 (The "After Party")<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgbGE4poNXdGBVOsC8NtCzzCJ91G2atIx6SjKVzzAXISQ7t2kfu8punRgLXkDktr12CSqBe-KgdnZpvGG_ssB1DleOS8NpMGwgDbYA1EsA5sfDzn7vxyShPuTthpIo27320udW4aze5qT4/s1600/Roval_side.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-family: "arial" , "helvetica" , sans-serif;"><img border="0" height="350" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgbGE4poNXdGBVOsC8NtCzzCJ91G2atIx6SjKVzzAXISQ7t2kfu8punRgLXkDktr12CSqBe-KgdnZpvGG_ssB1DleOS8NpMGwgDbYA1EsA5sfDzn7vxyShPuTthpIo27320udW4aze5qT4/s400/Roval_side.JPG" width="400" /></span></a></div>
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<span style="font-family: "arial" , "helvetica" , sans-serif;">About a week after the fun session in the Specialized Win Tunnel (outlined in <a href="http://bikeblather.blogspot.com/2015/10/win-tunnel-playtime-part-1.html" target="_blank">Part 1</a> and <a href="http://bikeblather.blogspot.com/2015/10/win-tunnel-playtime-part-2.html" target="_blank">Part 2</a>), I received an email from Cam Piper which included "wheel only" data for the Roval CLX64 wheel and each model size of both the S-Works Turbo (22C, 24C, 26C, and 28C) and Turbo Cotton (24C and 26C) tires. At the time I visited I had asked about this data set, and although they had all the data, it wasn't easily collated into a single file. So, on the following Friday, Cam took on the (large) task of running and procuring a dataset for all of those tires in a single session. That data is summarized in the CdA vs. yaw angle plot below:</span></div>
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Roval CLX64 Wheel</span></h3>
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<span style="font-family: "arial" , "helvetica" , sans-serif;">As one can see, that's a really nice data set, especially the symmetry. Also, one can clearly see the effect of tire size on drag, especially with the S-Works Turbo sizes. In regards to size, it's important to note that the listed tire sizes typically "grow" by ~2mm when mounted to a wheel with such a wide interior bead width, such as the Roval CLX64 (nearly 21mm, if I recall correctly). For example, the 22C S-Works Turbo actually measured slightly >24mm wide when installed on that wheel.</span></div>
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<span style="font-family: "arial" , "helvetica" , sans-serif;">Not long after receiving this data, I also received a box from Specialized containing samples of each of the listed tires for me to roller test personally for Crr. Wow...that's a lot of tires to test, plus at the time I didn't have a bike capable of testing the 28C S-Works Turbo when mounted on a wide rim. Luckily, I was in the process of building up a "gravel bike" (based on a 26" rigid MTB frame...I digress...) and so eventually I could get the Crr data for that one as well. </span></div>
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<span style="font-family: "arial" , "helvetica" , sans-serif;">When the tires arrived, I realized that it may be time to revisit my tire testing protocol and tweak things to make the process more amenable to testing wider tires. When I started roller testing tires, I was mainly looking at TT tires and wheels of the time were still significantly narrower than they are today, so testing at 120 psi seemed reasonable. However, as rims and tires have gotten wider, I've been uncomfortable with pumping tires like 26C and 28C models up to 120 psi to test...and in fact, have had a couple cases where I couldn't get tires that wide to stay on the rims when inflated! Knowing that, while testing this batch of Specialized tires I decided to do some narrow (Mavic Open Pro) vs. wide (Hed Jet+) rim testing along with tests at 120 psi and 100 psi. To make a long story short, I found that in general, a tire will roll approximately the same on my rollers on a narrow Open Pro rim at 120 psi as it will on the extra wide Jet+ rim at 100 psi. That was a valuable thing to discover, and it means that my future tests will be run at 100 psi on a 20.5-21mm internal width diameter rim. I especially wanted to test all of these tires on a wide internal width rim for Crr so that it would best match the tires as mounted on the Roval CLX64 wheels used in the aero testing.</span><br />
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<span style="font-family: "arial" , "helvetica" , sans-serif;">The Crr results for the 6 Specialized tires are as follows:</span><br />
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<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; line-height: 18.48px;">Specialized S-Works Turbo 22C = .0041, 38W for pair @ 40kph</span><br />
<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; line-height: 18.48px;">Specialized S-Works Turbo</span><span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; line-height: 18.48px;"> 24C = .0036, 33W for pair @ 40kph</span><br />
<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; line-height: 18.48px;">Specialized S-Works Turbo</span><span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; line-height: 18.48px;"> 26C = .0035, 32W for pair @ 40kph</span><br />
<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; line-height: 18.48px;">Specialized S-Works Turbo</span><span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; line-height: 18.48px;"> 28C = .0035, 32W for pair @ 40kph (note: AC101 disc wheel)</span><br />
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<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; line-height: 18.48px;">Specialized Turbo</span><span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; line-height: 18.48px;"> Cotton 24C = .0029, 27W for pair @ 40kph</span><br />
<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; line-height: 18.48px;">Specialized Turbo</span><span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; line-height: 18.48px;"> Cotton 26C = .0028, 26W for pair @ 40kph</span><br />
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<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; line-height: 18.48px;">By comparison, here's the results for the "benchmark" GP4000S (tested on Open Pro @120psi):</span><br />
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<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; line-height: 18.48px;">Continental GP4000S 23C = .0034, 31W for pair @ 40kph</span><br />
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<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; line-height: 18.48px;">There are a couple of interesting takeaways in those results. First, I was somewhat surprised at the seemingly non-proportional "hit" in Crr the 22C S-Works Turbo took in comparison to the 24 and 26C sizes. It was also interesting that 28C size basically rolled the same as the 26C size, although that may be attributable to the fact the 28C was tested on a low profile, 32 round spoke disc brake wheel, while the 26C was tested on a Hed Jet6+ deep wheel with bladed spokes. One other interesting result is that in the Turbo Cottons, the 26C tire rolled only slightly faster than the 24C. This may mean that the Crr of that tire model is driven more by the tread composition (both tires appear to use the same width tread) than by the casing material properties. Lastly, these results appear to confirm that the S-Works Turbo tires in the 24C and 26C sizes are basically "tied" with the Continental GP4000S in terms of Crr (remember that I consider anything within .0001 of Crr to be "tied").</span><br />
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<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; line-height: 18.48px;">OK...so, if any of you have read some other blog posts of mine, you probably know where this is going. Yep...what does it mean when we combine the Crr and CdA results? Which of the tires above gives the best combination of rolling resistance AND aero for a particular application? </span><br />
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<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; line-height: 18.48px;">Well, to truly get at that answer requires some fairly detailed modeling, such as that performed by <a href="http://bestbikesplit.com/">BestBikeSplit.com</a>, for example. However, it's possible to at least get an inkling of which tire may give the best combo using some simple assumptions. In this case, I made the assumption that the wheel load is 38kg (~45% of my typical "all up" mass of 85kg, typical of a front wheel for me) and a ground speed of 35 kph (~22 mph). Figuring out the power for each tire at that speed is easy, and is merely Crr x Speed x Mass x gravity.</span><br />
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<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; line-height: 18.48px;">The expected power for the aero drag is slightly more difficult...and involves using the apparent wind speed expected for the particular ground speed AND yaw angle. It's probably easier to explain with some vector diagrams (and I'll do that if the interest is shown), but suffice to say that if your ground speed is 35 kph AND you have a non-zero yaw angle, then the apparent wind acting on the rider is going to be greater than 35 kph. It's important to remember that the results coming from a wind tunnel are the CdA (or sometimes grams of drag) in the body axis of the wheel, or bike, for a given APPARENT wind speed (typically set to ~30mph for better resolution). So, what that means is that there is some trigonometry that needs to be undertaken for non-zero yaws for the power calculation. In this simplified analysis, it's also an assumption that any sidewind is a "pure" crosswind, or oriented 90 degrees to the riders travelling path. Thankfully, the data acquisition setup at the Specialized Win Tunnel already does that trigonometry for us. This is sometimes referred to a "beta correction" in wind tunnel parlance.</span><br />
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<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; line-height: 18.48px;">So, I set up a spreadsheet to handle all of that, and here's the expected combined power for a single wheel with a 38kg load, travelling at 35 kph.</span><br />
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<span style="background-color: white; color: #222222; font-family: "arial" , "tahoma" , "helvetica" , "freesans" , sans-serif; line-height: 18.48px;">Roval CLX64, 38kg load, 35 kph ground speed</span></h3>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhnSvY8jcZ-YkUFfMfzhrJlcHo_9U6gcp6prG9RrjzINxiwkYFMlTBWg-4W5iR2FmHdIH2Jf8i3A8gg2iacB5w5jp_W1vlbrf4tj_najDnZkYo8Epz0Cx6_J-e3fIFgjFYJCvWkxdWEoiU/s1600/Tires_Total_Pwr_2.JPG" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="462" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhnSvY8jcZ-YkUFfMfzhrJlcHo_9U6gcp6prG9RrjzINxiwkYFMlTBWg-4W5iR2FmHdIH2Jf8i3A8gg2iacB5w5jp_W1vlbrf4tj_najDnZkYo8Epz0Cx6_J-e3fIFgjFYJCvWkxdWEoiU/s640/Tires_Total_Pwr_2.JPG" width="640" /></a></div>
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<span style="font-family: "arial" , "helvetica" , sans-serif;">So, what can we take from that plot? As I've said previously, "Low rolling resistance can make up for a LOT of 'aero sins' " (<a href="http://bikeblather.blogspot.com/2013/04/why-tire-crr-matters.html" target="_blank">Here</a>, and <a href="http://bikeblather.blogspot.com/2013/08/even-more-crr-resultsand-another.html" target="_blank">here</a>)...and that plot above helps bring that home. Although the S-Works Turbo 22C tire was the clear leader in the CdA plot, when combined with the expected Crr of the tires, it actually isn't as good as any of the other tires at 10 degrees and below of yaw angle. In my view, the Turbo Cotton tires are the clear winners in the combined power plot, with the edge going to the 24C version, at least in my mind. The total power at 0 and 5 degrees are basically identical, but the 24C has a slight edge at 10 degrees. At 15 degrees, the 2 tires are tied again.</span></div>
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<span style="font-family: "arial" , "helvetica" , sans-serif;">In looking at the S-Works Turbo tires only, it appears that the best overall of the bunch is the 24C model, with the 26C nearly tied with it.</span><br />
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<span style="font-family: "arial" , "helvetica" , sans-serif;">Now obviously, that's the results for that given load and ground speed. For different wheel loads, the Crr contribution is going to vary proportionally up and down relative to the load, and for different ground speeds, the aero proportion is going to vary with the cube of the ground speed up and down. So, for lighter and/or faster riders than what is assumed, the aero effects will be relatively more important, while for heavier and/or slower riders the Crr effects will be relatively more important.</span></div>
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<span style="font-family: "arial" , "helvetica" , sans-serif;">After calculating these results, of course I also applied them to the wheel and tire combos that were taken during my Win Tunnel visit. To remind everyone of the CdA plot of all of the combos looked, here it is again:</span></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjqipdu6-CvnmaennnTngCVinzMCQwYqIqxqKwxY0HLZXPGYp3dtddEMN4JnCf6QpNcjwLVeZg52lCoVf1cQI-JfBqY-Q8RWlfWOEAyCTQRVZeYQlmcEjVLdUVmVj7wzpX6wG1Erd_VZeY/s1600/AllWheels.JPG" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="464" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjqipdu6-CvnmaennnTngCVinzMCQwYqIqxqKwxY0HLZXPGYp3dtddEMN4JnCf6QpNcjwLVeZg52lCoVf1cQI-JfBqY-Q8RWlfWOEAyCTQRVZeYQlmcEjVLdUVmVj7wzpX6wG1Erd_VZeY/s640/AllWheels.JPG" width="640" /></a></div>
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<span style="font-family: "arial" , "helvetica" , sans-serif;">Combining that plot with the Crr results like we did above, results in the following overall expected power plot:</span></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEitlXf2SoGAxmSgWamidMTLQPWO650VNPfw32RAiDEhzz3j5Bn_dSIdJYg-LlPbYEEuuxULqvR8EaMDAC0wqyyymhSCIxwmR3AJpExelwkK5lVaDq8HfbX0Nz3_a-P_YIrl9mx-r4JQek0/s1600/All_Wheels_Total_Pwr_2.JPG" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="462" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEitlXf2SoGAxmSgWamidMTLQPWO650VNPfw32RAiDEhzz3j5Bn_dSIdJYg-LlPbYEEuuxULqvR8EaMDAC0wqyyymhSCIxwmR3AJpExelwkK5lVaDq8HfbX0Nz3_a-P_YIrl9mx-r4JQek0/s640/All_Wheels_Total_Pwr_2.JPG" width="640" /></a></div>
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<span style="font-family: "arial" , "helvetica" , sans-serif;">I think I'll just leave that there without further comment...Enjoy!</span><br />
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<span style="font-family: "arial" , "helvetica" , sans-serif;">The spreadsheets containing the data and calculations can be viewed here:</span><br />
<span style="font-family: "arial" , "helvetica" , sans-serif;"><a href="https://docs.google.com/spreadsheets/d/1KYjws700q6aWCrdMjFXeUrQrWAtMwbuVVVjtg9m6ebo/edit?usp=sharing" target="_blank"><br /></a></span>
<span style="font-family: "arial" , "helvetica" , sans-serif;"><a href="https://docs.google.com/spreadsheets/d/1KYjws700q6aWCrdMjFXeUrQrWAtMwbuVVVjtg9m6ebo/edit?usp=sharing" target="_blank">- Roval CLX64 plus Specialized Tires</a></span><br />
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<span style="font-family: "arial" , "helvetica" , sans-serif;"><a href="https://docs.google.com/spreadsheets/d/1xCdKjHnIsHSOUJrADghGhXM_jYm90v9HYgsu1fEYAL0/edit?usp=sharing" target="_blank">- All wheels from Win Tunnel Visit</a></span><br />
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<i>edit 23Jan2017: After roller testing a newer version of the Continental SuperSonic in 2016, I found that it had significantly improved the Crr in comparison to the c2012 version I had previously tested. So, I decided to use the newer value in calculating the total power for the H3/Conti 20C SS combination in the chart above. With those changes, the chart looks as follows:</i><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi_AEsdUND4MByO8mWuH5uwSTV3CGLGXhGo3Ag9gVLoNENhmub9pP2lh362YRfirt3_sx955i3ExzNSJU3xj7t5ohjgkqahizJTeC2LB90LqBpNF17z9hIadYWkXtB3X4fc7HwP2rOzmJQ/s1600/Ttl_Pwr_2.JPG" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="464" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi_AEsdUND4MByO8mWuH5uwSTV3CGLGXhGo3Ag9gVLoNENhmub9pP2lh362YRfirt3_sx955i3ExzNSJU3xj7t5ohjgkqahizJTeC2LB90LqBpNF17z9hIadYWkXtB3X4fc7HwP2rOzmJQ/s640/Ttl_Pwr_2.JPG" width="640" /></a></div>
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Tom Anhalthttp://www.blogger.com/profile/08175472546482777614noreply@blogger.com13tag:blogger.com,1999:blog-6080071290235905056.post-8697060717052915152015-10-25T18:46:00.000-07:002016-03-05T13:22:30.093-08:00Win Tunnel Playtime - Part 2<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiXrcY2OSN4YxLoltTkoHgUs4MEE2sEL0uRIKZD9TqSkR6x-NJxfzGUBIM8LFSA25RuICwzjxHQKGShUprrM4-Tr0UiWypG05ImmkV6MZc_crvHjtXlLHVPdbkBcugGtenbu_X3v3wTyeQ/s1600/Front_164853_160+%25282%2529.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="368" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiXrcY2OSN4YxLoltTkoHgUs4MEE2sEL0uRIKZD9TqSkR6x-NJxfzGUBIM8LFSA25RuICwzjxHQKGShUprrM4-Tr0UiWypG05ImmkV6MZc_crvHjtXlLHVPdbkBcugGtenbu_X3v3wTyeQ/s640/Front_164853_160+%25282%2529.jpg" width="640" /></a></div>
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In the previous blog post (<a href="http://bikeblather.blogspot.com/2015/10/win-tunnel-playtime-part-1.html" target="_blank">Win Tunnel Playtime - Part 1</a>), I described how this particular adventure came about, and I presented the bulk of the data collected, which was the result of a large amount of wheel and tire testing. In this post, I'll be covering the remaining testing we did on that day. In short, we did a small number of bike-only runs, varying the front wheel on the bike. This was done in an attempt to see how the differences in drag compared to the wheel-only runs for changes in front wheels. Most of the testing was done using my personal bike (a <a href="http://www.stinnerframeworks.com/" target="_blank">Stinner Frameworks</a> custom steel road frame), and for comparison sake, we also tested a brand new <a href="http://www.specialized.com/us/en/bikes/road/venge" target="_blank">Specialized Venge ViAS</a> which just happened to be available <smirk>.<br />
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So...let's get to it. Shown below is a summary plot of all of the bike-only runs. As a bit of explanation, the combinations tested were as follows:<br />
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<li>Stinner with Hed Jet6+ wheels and 24C Specialized Turbo Cottons. Specialized Virtue bottle. This setup represents my own personal rig, set up in what I like to call "crit mode".<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhmhIhCRZxoaPGloWLiRkRhZboZHebzSUWCMlTBQ2iOxhKyVw8-RMqpSx5-r_V-F4vVmYN0Ix9wexkK4zNqgtsxmUwHAXp3adF8svliZaBhecO6fKw6z7H7HNkOOgryFFRTY5Gi6MWvdwo/s1600/Right_150057_116.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhmhIhCRZxoaPGloWLiRkRhZboZHebzSUWCMlTBQ2iOxhKyVw8-RMqpSx5-r_V-F4vVmYN0Ix9wexkK4zNqgtsxmUwHAXp3adF8svliZaBhecO6fKw6z7H7HNkOOgryFFRTY5Gi6MWvdwo/s400/Right_150057_116.jpg" width="400" /></a></div>
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<li>Same as #1, with front wheel swapped for a Roval CLX64 with a 22C Specialized S-Works Turbo tire.<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiwq1Q6_UpfH4ZAHA9ADecbtdNX9mqIWZCh8HV_CjFYkB5s3qcZAIj50KpLto-Y_8TVPA0_VPuhsuP6cL81SV_lDh3Dk5Wqpuhg3PAm0RmzlBm7m2H6pNWa1l3Ad9CvrC-oqXN4v9b0hts/s1600/Right_151418_123.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiwq1Q6_UpfH4ZAHA9ADecbtdNX9mqIWZCh8HV_CjFYkB5s3qcZAIj50KpLto-Y_8TVPA0_VPuhsuP6cL81SV_lDh3Dk5Wqpuhg3PAm0RmzlBm7m2H6pNWa1l3Ad9CvrC-oqXN4v9b0hts/s400/Right_151418_123.jpg" width="400" /></a></div>
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<li>Same as #1, but with front wheel swapped for Flo 90 with 23C Continental Super Sonic tire.<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhqDuN9Wlo7QR9hUtVw-VaJQ5khcBdajoXH-jfT7N14gQGkpRS8b4SExMZ477FsmHDwvsm2NBrrclIY8e6t6l9OANI8iZJzmbdlc_XygfHGjdCNbfi1c44QY5A3irGPUQIxTVhd-zSD_e4/s1600/Right_152549_130.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhqDuN9Wlo7QR9hUtVw-VaJQ5khcBdajoXH-jfT7N14gQGkpRS8b4SExMZ477FsmHDwvsm2NBrrclIY8e6t6l9OANI8iZJzmbdlc_XygfHGjdCNbfi1c44QY5A3irGPUQIxTVhd-zSD_e4/s400/Right_152549_130.jpg" width="400" /></a></div>
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<li>Same as #3, but with round bottle and bottle cage swapped over from Venge ViAS frame on downtube (low location).<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi2Pl31Sg4h4Gc-P41px6vQ_aJ0sKYGDGnsHJXC9oYzeZPEXRreOK4IjQOeeRS1zQ6e_T6TNoRPQH6obqdnsQQ1eXveLA0rKKztyHQ8Ns35YGHAT6VriKJFuEvY6VmCM03rL_0lZrxAl0c/s1600/Right_154039_137.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi2Pl31Sg4h4Gc-P41px6vQ_aJ0sKYGDGnsHJXC9oYzeZPEXRreOK4IjQOeeRS1zQ6e_T6TNoRPQH6obqdnsQQ1eXveLA0rKKztyHQ8Ns35YGHAT6VriKJFuEvY6VmCM03rL_0lZrxAl0c/s400/Right_154039_137.jpg" width="400" /></a></div>
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<li>Venge ViAS with Roval CLX64 wheels, 22C Specialized S-Works Turbo front, 24C rear. Round bottle on downtube.<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh51TtOx8Hm8Jb4Hc995hY1Uif4M9PiBxS-tJH_YPINCidCar-ohWDbzYlNhQdPRoJcsovAAT1NGOEvRFrDoeVHB4ZjZLnR3Wu3bo1C00cjylay7V9aSiptlIo0R6izKEwYhpypRPpHYjc/s1600/Right_160014_144.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh51TtOx8Hm8Jb4Hc995hY1Uif4M9PiBxS-tJH_YPINCidCar-ohWDbzYlNhQdPRoJcsovAAT1NGOEvRFrDoeVHB4ZjZLnR3Wu3bo1C00cjylay7V9aSiptlIo0R6izKEwYhpypRPpHYjc/s400/Right_160014_144.jpg" width="400" /></a></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiFNa6V3dZD05E3zow4Z7s6S93z7Fa9k5vjA7U8237y7adsqQvldn7wkGc4jLq0P14KnHAHOfqm8KWvNrHf-nt3T6JS-qjq139GS0qCoBx3wio9SH2zpvxS1l0_cDSYBgmPzNqnaL_JBxw/s1600/BikeAlone.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="460" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiFNa6V3dZD05E3zow4Z7s6S93z7Fa9k5vjA7U8237y7adsqQvldn7wkGc4jLq0P14KnHAHOfqm8KWvNrHf-nt3T6JS-qjq139GS0qCoBx3wio9SH2zpvxS1l0_cDSYBgmPzNqnaL_JBxw/s640/BikeAlone.JPG" width="640" /></a></div>
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Aside from how impressively low the drag is for the Venge ViAS in that chart above, what is particularly interesting is how those 3 upper plots (with the same bottles on the bike) compare to each other, AND to the wheel-only data. To do that comparison, I looked at the differences seen between those particular combinations of wheels and tires during the wheel-only testing and compared them to the bike testing. Those comparisons are summarized in the following 3 charts.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEip3gSv2jYWbeELrnlBkp7JW_b_mO99udMPmod5UatgvDOkCKhfZEG1juEHPLyIIQb6WLvyoWeW6TacoNvAMW_7Dj4wMQrAOd7P8Z-A5KFaVdqB7yY0nQhS08nt0M7v3rk_yythy4Bhez4/s1600/Wheel+Diff+Roval+v+Jet6.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="306" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEip3gSv2jYWbeELrnlBkp7JW_b_mO99udMPmod5UatgvDOkCKhfZEG1juEHPLyIIQb6WLvyoWeW6TacoNvAMW_7Dj4wMQrAOd7P8Z-A5KFaVdqB7yY0nQhS08nt0M7v3rk_yythy4Bhez4/s640/Wheel+Diff+Roval+v+Jet6.JPG" width="640" /></a></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh8VPyk6q8rx_gGVDjjebrj_szSKuByCEJo1tjp-3Surbc84mOc_BFxVpXhhvbeTURGGGjvZ4R-AZIpmsV1gmu3MYDHT6lnHMuvjEPd-VB1hdRFAq0dXGd28RmB9NV86cqSAdf4rkkbmv4/s1600/Wheel+Diff+Roval+v+Flo90.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh8VPyk6q8rx_gGVDjjebrj_szSKuByCEJo1tjp-3Surbc84mOc_BFxVpXhhvbeTURGGGjvZ4R-AZIpmsV1gmu3MYDHT6lnHMuvjEPd-VB1hdRFAq0dXGd28RmB9NV86cqSAdf4rkkbmv4/s640/Wheel+Diff+Roval+v+Flo90.JPG" width="640" /></a></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjHr5APlmIifhRApG-IZ1AVNFyVCtM2Q3H6V48Hhps5JPqSZb8q1ZZwv3CirAJfRcDhy1QGECkMtsEdJIWI-qgczYeISdKOA6RM_SsfgbocZjNuwySfybEjePwntt5fw8lfkUOPFNMoqS4/s1600/Wheel+Diff+Flo90+v+Jet6.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="298" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjHr5APlmIifhRApG-IZ1AVNFyVCtM2Q3H6V48Hhps5JPqSZb8q1ZZwv3CirAJfRcDhy1QGECkMtsEdJIWI-qgczYeISdKOA6RM_SsfgbocZjNuwySfybEjePwntt5fw8lfkUOPFNMoqS4/s640/Wheel+Diff+Flo90+v+Jet6.JPG" width="640" /></a></div>
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What we can see from the above is that in most cases the differences in drag observed from wheel only data are within 0-.002 m^2 of the differences observed when those same wheels are swapped for the front wheel in a bike. There are a couple of differences that vary by .003m^2 in that data, but overall I'd have to say that the "predictive" utility of how a front wheel will perform within a bike based on wheel only data is pretty good.</div>
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Now we get to the part where we put a "floppy human" (me!) on board and see what happens. Due to time constraints, for this portion of the data gathering we only took 2 yaw data points (0 and 10 degrees), which each consisted of 60s of sampled data. Since the Venge ViAS was there (and in my size!) of course I made sure to get a set of runs in on that. Since the Venge was the last bike from the bike-only runs and was already mounted to the tunnel balance platform, that was the first up.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgg57ebtB-a4-SeRCCfuwJEfpVKjx-b1rthY-RIpOhcZD3Ol53eONimerL5CJK0xkRYAB_F7XiG2mTBg_wqDxT6OJBqcwwq3IkIKKs4AF3aeN9KPTs5dKIg5T_4QpMmL4-xEO5JGyxQ9-E/s1600/Right_161941_149.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgg57ebtB-a4-SeRCCfuwJEfpVKjx-b1rthY-RIpOhcZD3Ol53eONimerL5CJK0xkRYAB_F7XiG2mTBg_wqDxT6OJBqcwwq3IkIKKs4AF3aeN9KPTs5dKIg5T_4QpMmL4-xEO5JGyxQ9-E/s400/Right_161941_149.jpg" width="400" /></a></div>
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Next was the Stinner with the Hed Jet6+ and Turbo Cotton tires (in my "crit setup")</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi61KMn7odzJqUFJHSPPcHwvU8SkwnWEJJ0ASlm6-Pxabx1MwBAiuOqQRsfrrNXzZQ9QMSTuTkUGD6vBcUKrmF6AiwXwEl-nLGMNu7Q2ZZNBqFujf3tTSVbhhqWZbmiA3KpY67hct8ZVVk/s1600/Right_163338_153.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi61KMn7odzJqUFJHSPPcHwvU8SkwnWEJJ0ASlm6-Pxabx1MwBAiuOqQRsfrrNXzZQ9QMSTuTkUGD6vBcUKrmF6AiwXwEl-nLGMNu7Q2ZZNBqFujf3tTSVbhhqWZbmiA3KpY67hct8ZVVk/s400/Right_163338_153.jpg" width="400" /></a></div>
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And finally, we swapped the front wheel for the Roval CLX64 and 22C S-Works Turbo.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgfQx11BWaVmZ7rt9f6v9eYcrZczMen7REYxMxg5tefm4EyaE0SrJvNlDICGeEbyzuIZYh4SZAumOW74ICbkcGlMvf9jNlcVlu_yslf_6-4Jsd4xkc-wFAw-I-PHNZGv8fGHZv9uRrrlFU/s1600/Right_164358_157.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgfQx11BWaVmZ7rt9f6v9eYcrZczMen7REYxMxg5tefm4EyaE0SrJvNlDICGeEbyzuIZYh4SZAumOW74ICbkcGlMvf9jNlcVlu_yslf_6-4Jsd4xkc-wFAw-I-PHNZGv8fGHZv9uRrrlFU/s400/Right_164358_157.jpg" width="400" /></a></div>
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Here's how that all played out:</div>
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As you can see, the difference at zero yaw between the Roval wheel and the Jet 6+ (as configured) was ~.003 m^2, which compares pretty favorably with the ~.002-.003 m^2 observed in the wheel-only and the bike-only testing for those combinations. </div>
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At 10 degrees of yaw, the difference appears to be somewhat larger, with the bike-with-rider testing showing a difference of ~.012 m^2 whereas the bike and wheel-only testing was more like .006-.007 m^2 of difference observed.</div>
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What's truly interesting though, is how closely the overall drag was brought together between the Stinner and the Venge ViAS when a rider is on board. At zero and 10 degrees of yaw, the drag difference appears to be less than half of what was observed in the bike-only testing. This puts my overall drag when on the Stinner to within .004-.006 m^2 of what it was on the Venge ViAS at zero and 10 degrees of yaw. Obviously, there must be something going on with bike interactions near the rider. Also, it's important to point out that the comparison between the bikes wasn't completely "apples to apples" since the water bottles were different. However, the Venge ViAS is designed to be basically "bottle neutral", so that's not too big of a factor. Another difference was that the bars were not identical, neither in model or in width. But again, the bars on the Stinner, although slightly narrower (40 vs. 42 for the Specialized bar) also have drops which are deeper...so, that probably ends up being a "wash" in the bike-only testing.</div>
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So...another large dump of data...with a few good conclusions. It appears that when making changes to the "leading edges" of the bike equipment (such as wheels, forks, bars, etc) drag differences observed in component-only and bike-only testing "hold" when applied to testing with a rider on board, at least for near zero yaw. However, that probably can't be said for pieces of the puzzle that are further back in the flow and interact more closely with one another.</div>
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As always, if you have any questions, just fire away in the comments...oh, and the data for this portion of the testing is found here: <a href="https://docs.google.com/spreadsheets/d/1NtLLrcpF5CeAX_S09qLfOzKlAegCFkA_o2UYPaQyf0g/edit?usp=sharing" target="_blank">Bike and Rider data</a></div>
Tom Anhalthttp://www.blogger.com/profile/08175472546482777614noreply@blogger.com17tag:blogger.com,1999:blog-6080071290235905056.post-60965549338425971942015-10-05T12:57:00.000-07:002015-10-06T09:27:49.831-07:00Win Tunnel Playtime - Part 1<div class="separator" style="clear: both; text-align: center;">
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgQn3Hd5jr7LA5Zmd7PAcLv5OefhiwGRpige-zuY57tXsjCDoACgxYqW9YXsOjLR1lhGdWhAeWSHcp8AMnNoWw32-e_Z0YzINj69cE4FjoPa5KyDl6JVB5J15SufOlmc34P6hA28iaWkvA/s1600/IMG_1105%255B1%255D.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="298" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgQn3Hd5jr7LA5Zmd7PAcLv5OefhiwGRpige-zuY57tXsjCDoACgxYqW9YXsOjLR1lhGdWhAeWSHcp8AMnNoWw32-e_Z0YzINj69cE4FjoPa5KyDl6JVB5J15SufOlmc34P6hA28iaWkvA/s400/IMG_1105%255B1%255D.JPG" width="400" /></a></div>
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As I mentioned in my last post, thanks to the generosity of <a href="http://www.specialized.com/us/en/location/" target="_blank">Specialized</a>, Chris Yu, and Cam Piper (both pictured above), I recently had the opportunity to spend a day in Morgan Hill, CA at Specialized's Win Tunnel facility. You're probably asking "How did THAT happen?" (something I asked myself repeatedly)...and well, it's a long story. I had met Chris Yu a few years back when I had the opportunity to observe the wind tunnel testing of my friend and professional triathlete, Jordan Rapp. At the time, Specialized had recently opened their "Win Tunnel" facility and I had a great time watching the proceedings and trying not to be too annoying in peppering Chris and Mark Cote with questions. Since that time, Chris and I had "conversed" on various forums, and even swapped a few emails.<br />
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Earlier this year, Chris had sent me an email asking if I was interested in participating in one of their <a href="https://www.youtube.com/playlist?list=PLcmaLnqmqDnmn_bCR0RJ-soSCDKCKR97t" target="_blank">videos</a> that they occasionally produce. I jumped at the opportunity and said "Sure!" and we planned on doing something in the July/August time frame. Well...one thing led to another, and the planned purpose of the video was changed...and then it turned out the video team wasn't going to be available on the dates we had planned. No worries though. As Chris explained to me, the tunnel time was already blocked out, and it turns out that like most forward thinking companies based in the SF Bay area (i.e. Google, Apple, etc.) Specialized allows their engineers time to "play", or pursue subjects that may not have an immediate application...on the thought that this "playtime" may spark some unexpected innovation. Chris told me we could brainstorm and come up with some things to look at, and like most tests, we'll most likely come up with some answers, but also some good additional questions to pursue. Sweet. How could I say no?<br />
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Due to the VERY large amount of data collected, what you'll see here in Part 1 is mostly the results of the morning of testing on that day in the Specialized Win Tunnel. I came up with the idea of trying a host of wheel and tire combinations, and then following it up with some of those same wheels and tires in bare bike tests...and then finally, I was hoping to get into the tunnel on a bike myself for a few runs. Shown below are the wheel/tire results. Part 2 (coming later) will show the remainder of the data. The idea was to see what sort of info could be gleaned about how wheel and tire combos are affected by the tire mounted (especially width) and if the differences observed "carried through" to both bare bike testing and testing with a rider. It was an "ad hoc" plan and group of equipment, but I figured at a minimum I would be getting a crash course in wind tunnel testing and the difficulties of doing so.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgouxu2IPlPojLshgyHWSk9OmlU9vYt-s0izrv5oTE94L_aAxYQpUqMpNIFNBI_w79cCMyTfxN-NrHkngJnq8KCAlrQpIyGJzAzPn4IDubUtSuTD-MQ6VejWVmF0Y_kxcXS_WQP_Ng2gko/s1600/Wheel+Matrix.JPG" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="100" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgouxu2IPlPojLshgyHWSk9OmlU9vYt-s0izrv5oTE94L_aAxYQpUqMpNIFNBI_w79cCMyTfxN-NrHkngJnq8KCAlrQpIyGJzAzPn4IDubUtSuTD-MQ6VejWVmF0Y_kxcXS_WQP_Ng2gko/s640/Wheel+Matrix.JPG" width="640" /></a></div>
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What you see above is the test matrix I put together for the wheel and tire testing. The wheels listed in the column on the left are the ones I would had available to me, and run the gamut from shallow to very deep. Across the top are listed the tires. Knowing that there was a limited time for the wheel/tire runs, I decided to go for a mix of tires on the wheels, with the one I was most interested in seeing was the one in the first column, the new S-Works Turbo 22C model. The greyed cells are the combinations tested, with the number in front of the hyphen the order in which they were to be tested. I wanted to make sure we weren't wasting time waiting for a tire to be swapped for a run. The number after the hyphen is the measured width, as mounted.<br />
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So, let's get to the data...but, before we do that, I want to point out how difficult it is to get "clean" data using equipment this sensitive. Seemingly small things can throw some of the results off...which is why it's good to have guys with tons of experience running the show. For example, when we ran the first runs using a "known" wheel/tire combo (the Roval CLX64 with S-Works Turbo 22C), Cam immediately noticed that the positive yaw values seemed "off"...and it was traced to simply an end cap on the wheel fixture not being fully seated. Anyway, after 11 runs, here's how the data looked as a whole.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhkFkQ_KDaV6VijECOh5X_mWbedpQlS6vLU-nyoDFUhR1z_mJbH6IG6Sr932MEsT2WGf6EUPBHNBwrj1RRETyBQnp6JVlqMVw1IEEaEhNx7wh6d7oFhTDSRuVP99vYLOZPV1iSuELD9iR4/s1600/AllWheels.JPG" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="464" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhkFkQ_KDaV6VijECOh5X_mWbedpQlS6vLU-nyoDFUhR1z_mJbH6IG6Sr932MEsT2WGf6EUPBHNBwrj1RRETyBQnp6JVlqMVw1IEEaEhNx7wh6d7oFhTDSRuVP99vYLOZPV1iSuELD9iR4/s640/AllWheels.JPG" width="640" /></a></div>
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The big takeaway there is that the Roval CLX64 w/S-Works Turbo 22C truly is the "benchmark" for this grouping of wheels and tires tested. The Jet 6+, also with the S-Works Turbo 22C tire, basically matches it, although at the positive 15 deg point there appears to be an asymmetry (which should probably be investigated - Is it the wheel? Fixture? Tire?). <br />
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Looking closer at just the Jet 6+ runs, here's how they looked:<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgf7SmbUl1QAn2HR9q4TpL4wjYWQdXm1u3ExJj8O1pDjyxO4jCWbzjdWiomal62NTMHMDcjSghD0yafY3XFYk44yQUM4BlygmhWmkTtpVPRTQV-Pmus2AyzvjCwgYtr7lZf6N5WBlBSki8/s1600/Jet6Plus.JPG" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="464" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgf7SmbUl1QAn2HR9q4TpL4wjYWQdXm1u3ExJj8O1pDjyxO4jCWbzjdWiomal62NTMHMDcjSghD0yafY3XFYk44yQUM4BlygmhWmkTtpVPRTQV-Pmus2AyzvjCwgYtr7lZf6N5WBlBSki8/s640/Jet6Plus.JPG" width="640" /></a></div>
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Another thing to note about the above data is that the Turbo Cotton 24C tire tested was my own personal tire with ~700 miles of front wheel use at that point. As can be seen, the wider 24C tire gives up some drag, not only at zero yaw, but especially so at the higher yaw angles. However, don't forget that the Turbo Cotton tires have VERY good Crr properties, so when we look at this data in an "overall speed" context, the differences may not be as large. THAT analysis will be done in a later blog post.<br />
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Another wheel tested was my personal Zipp 101 wheel. For this one, I wanted to see the effects of tire width for such a shallow wheel, so the comparison was between the S-Works Turbo tires in both the 22C and 24C sizes. As you can see, the 2mm wider tires results in a fairly fixed offset across the range of yaw angles tested:<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg6jiv8-RltPgcpUrpfvE1Vge1t-RWQipij8UL2ElRq1mW4TmlnNnHx2Vp_-fj1CWs5boK82HToh8qSPg7iw2BtviZSCWM1afBzXqCxQcV43jGK7uP1VsUP2w5u402JprHXf69VvERNE_g/s1600/Zipp101.JPG" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="464" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg6jiv8-RltPgcpUrpfvE1Vge1t-RWQipij8UL2ElRq1mW4TmlnNnHx2Vp_-fj1CWs5boK82HToh8qSPg7iw2BtviZSCWM1afBzXqCxQcV43jGK7uP1VsUP2w5u402JprHXf69VvERNE_g/s640/Zipp101.JPG" width="640" /></a></div>
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One of the things I wanted to check out in the wheel/tire testing was how well the venerable Specialized Trispoke/Hed H3 wheel performs vs. more modern wheels...plus, I wanted to see how well it worked with a VERY narrow tire, like it was designed around. As such, I took a brand new "out of print" Bontrager Aero TT 19C tire and compared it to the 20C Veloflex Record (that the wheel owner used as a tire) and also a 20C Continental Supersonic. As can be seen below, as compared to the Roval "benchmark", the older wheel leaves a bit to be desired, especially at yaw angles above 5 degrees. To be fair, this data doesn't include "power to rotate", which some claim can be a significant advantage for the Trispoke/H3. In any case, I think it's fair to say that of the tires tried, the 20C Continental Supersonic is probably the best combination of aerodynamics and Crr for that particular wheel.<br />
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Lastly, we looked at my personal Flo 90 front wheel, comparing the aero performance between a Continental Attack 22C, a Continental SuperSonic 23C, and an S-Works Turbo 22C tire. The surprising result there (for me, at least) was how well the SuperSonic tire performed out to 10 degrees of yaw as compared to the other slightly narrower tires. Combine that aero performance with the excellent Crr of that tire, and it looks to be a tough combo to beat as a front wheel application (I'll have more on the aero+Crr combos in a later blog post). It's also important to note how well the Roval CLX64 wheel performed vs. a wheel 26mm deeper!<br />
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That's about it for now for this blog post. There's a ton of data I'd like to go through, and I figured it was high time I started sharing some of this stuff. I wanted to throw this stuff out there first to generate discussion. I'll have more analysis later.<br />
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For those interested, the entire data set can be found in this spreadsheet here: <a href="https://docs.google.com/spreadsheets/d/11Wl--7pWryJsX6Ctn_bqmDbkaH7hErc2dSkyY6KBFl4/edit?usp=sharing" target="_blank">Wheel Aero Data</a>Tom Anhalthttp://www.blogger.com/profile/08175472546482777614noreply@blogger.com18tag:blogger.com,1999:blog-6080071290235905056.post-81361225791488840462015-09-07T16:26:00.001-07:002015-09-07T16:30:10.602-07:00Getting Caught Up...Yeah...I know...it's been about a year since I posted to this blog. Lots of "life" happening here. Anyway, I recently had an unbelievable opportunity to "play" with Chris Yu and Cam Piper at the Specialized "Win Tunnel", and before getting into and (over?)analyzing the data from that adventure (we're talking wheel and tire combos, bare bikes, and even rider-on testing!), I thought it would be good to get my Crr spreadsheet up to date. I did test a few tires over the past year...not many...with the majority of what's been added being various flavors of Continental tires.<br />
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The spreadsheet linked to in the upper right corner of this blog page has had the following entries added:<br />
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Continental Supersonic 23C (New) = .0029, 27W for pair @ 40kph<br />
Continental Attack 22C (~140 miles, "magic tire") = .0029, 27W for pair @ 40kph<br />
Continental Force (used) = .0034, 32W for pair @ 40kph<br />
Continental Attack 22C (ave. of 2 new) = .0036, 33W for pair @ 40kph<br />
Continental Attack 22C (1 of 2 above, 118mi) = .0036, 33W for pair @ 40kph<br />
Clement Strada LGG Gumwall 25C = .0045, 42W for pair @ 40kph<br />
Kenda Kountach 25C = .0049, 45W for pair @ 40kph<br />
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So...a bit of discussion about those results above, especially in regards to the Attack models. As of now, I've tested a total of 4 Attack tires, with 3 of them being new and all of the new tires rolling ~the same at .0035-.0036. Even when taking one of those tires and putting ~120 miles on it, the Crr did not appear to change appreciably. However, there was one Attack that was sent to me with what was claimed to have only ~140 miles on it...and that one rolled SIGNIFICANTLY faster at .0029. That's the one I call the "magic" tire. Knowing this, I would have to say that for anyone who wishes to run a Conti Attack as a TT/Tri tire, I would highly recommend roller testing the particular tire to make sure you have one of the lower Crr versions. For me, the majority of the Attack tires I've rolled have all been significantly slower. It might take quite a few tials...<br />
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The other interesting data point is the used Conti Force tire. I had previously rolled another lightly used Force tire at .0029, as opposed to this particular one at .0034. Again, like with the Attacks, it appears the Crr for these tires from Conti is highly variable.<br />
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The new 23C Continental Supersonic tested out at what I had previously estimated a new one would based on a well-used version I tested back in July of 2014, at .0029 vs. .0027. That ties it with the excellent Specialized S-Works Turbo Cotton 24C.<br />
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Well...that's about it for now. The spreadsheet is updated with the tires I've tested in the past year. Look for a couple of posts soon on my Specialized adventure!Tom Anhalthttp://www.blogger.com/profile/08175472546482777614noreply@blogger.com5tag:blogger.com,1999:blog-6080071290235905056.post-56645551037017702212014-10-29T11:48:00.000-07:002020-05-04T16:26:11.833-07:00An Oldie, but a Goodie...Field Testing Frame Differences with a Power Meter<br />
I originally posted this back in 2008 on the Slowtwitch.com forum and
is an example of the types of equipment differences that can be
determined with careful field testing. Here's the link (click on the title below) to the full
thread on Slowtwitch...it's long but informative, and there's some
pretty good "back and forth" with a few <i>skeptics</i>:<br />
<br />
<h2 style="text-align: center;">
<a href="http://forum.slowtwitch.com/gforum.cgi?post=1802183;#1802183" target="_blank">Something Borrowed...Something Fast!</a></h2>
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So take this guy and his position: <br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgwHBmUCoUSu1l3wLWbjhr-r9hy3hkY38wpl18C5Jt0l9YAcl9MngERfX7Kyl66RxSn44YyJhPzO_xZzyyPT4Yw0Q3lPU3RGRZRKzb0gB1iM7-FcT-fOtGJvkvogca8sRMGDsB2NXTFhFI/s1600/3096-large_MonTT908.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" data-original-height="400" data-original-width="499" height="512" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgwHBmUCoUSu1l3wLWbjhr-r9hy3hkY38wpl18C5Jt0l9YAcl9MngERfX7Kyl66RxSn44YyJhPzO_xZzyyPT4Yw0Q3lPU3RGRZRKzb0gB1iM7-FcT-fOtGJvkvogca8sRMGDsB2NXTFhFI/s640/3096-large_MonTT908.jpg" width="640" /></a></div>
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...and put him on this guy's bike and adjust it so that they fit identical. <br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEikhZJSUfozi0ZtkeTDt7dyWeQQzqiPhqRH8u800EewUSvcwbYw9Fi8uLiiX7R81UeUrm-KNelSXKQmKrzfffw16PrynLtJ70VhMCrUU4XlJQlZbGXxISi3zI-HZ07_do66vdCUERqmTBc/s1600/11400.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="800" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEikhZJSUfozi0ZtkeTDt7dyWeQQzqiPhqRH8u800EewUSvcwbYw9Fi8uLiiX7R81UeUrm-KNelSXKQmKrzfffw16PrynLtJ70VhMCrUU4XlJQlZbGXxISi3zI-HZ07_do66vdCUERqmTBc/s640/11400.jpg" width="640" /></a></div>
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<br />
Then,
let the first guy test both of these "back to back" using the same 404
wheelset with PT SL hub and cover....Any guesses on what the aerodynamic
drag differences (if any) one would see? <br />
<br />
Using RChung's most excellent methodology described here: <a href="http://anonymous.coward.free.fr/wattage/cda/indirect-cda.pdf" target="_blank">Method to the madness</a><a href="http://anonymous.coward.free.fr/wattage/cda/indirect-cda.pdf" target="_blank"> </a><br />
<br />
Here's the results for the P2K with the 404 wheels (the wheels on the P3C above): <br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjB5Qc0y9QhiVZWbCijW8KFL1OACm71pmrCZe6A1OhrmQ3L5jN03PveXN6Fmozd4_N986TkG0NmmZO2oy8uX48KJ_T6lmHsZxM-1idneMXtpmJWlJNSvBxNfeSZgrCKmgpfdpKAoc44VNU/s1600/P2Kanalysis.PNG" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" data-original-height="998" data-original-width="1280" height="498" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjB5Qc0y9QhiVZWbCijW8KFL1OACm71pmrCZe6A1OhrmQ3L5jN03PveXN6Fmozd4_N986TkG0NmmZO2oy8uX48KJ_T6lmHsZxM-1idneMXtpmJWlJNSvBxNfeSZgrCKmgpfdpKAoc44VNU/s640/P2Kanalysis.PNG" width="640" /></a></div>
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And here's the results for the P3C:<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg2pB9m11zaHOG7xLnjENZPh8VL2QlaVRfyteOy3QrMWqpl3wGQa74IzwHfXqXWsP5tb6iSkvnANcAghV8e1nt1BBEJVVIGq3Pvh5Cdw9qAhN_nA-u1HOISMESSLSE7nTdnUEZMBzF0Yu0/s1600/P3Canalysis.PNG" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" data-original-height="998" data-original-width="1280" height="498" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg2pB9m11zaHOG7xLnjENZPh8VL2QlaVRfyteOy3QrMWqpl3wGQa74IzwHfXqXWsP5tb6iSkvnANcAghV8e1nt1BBEJVVIGq3Pvh5Cdw9qAhN_nA-u1HOISMESSLSE7nTdnUEZMBzF0Yu0/s640/P3Canalysis.PNG" width="640" /></a></div>
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<br />
So...what's the bottom line? <br />
<br />
Well...taking
the same rider, the same wheels, the same basebars and brake levers,
and with the seat and extensions adjusted to deliver the same
positions...at basically zero yaw conditions I apparently measured a
drag difference of ~.023 m^2 of CxA (or Cda, whichever you prefer - .228
m^2 for the P2K and .205 for the P3C). Using Doc C's "rule of thumb",
that basically equates to ~2.5s per km of time savings. <br />
<br />
With
only an extremely small amount of crosswind however (I could just barely
detect it on my skin, not enough to even move leaves on trees), the
drag on both setups drops significantly, with the P3C setup dropping
more at .190 m^2 vs. the P2K's .220 m^2 for a growing difference of ~.03
m^2. That translates to a difference of ~3 seconds per km...or a full 2
minutes over 40K. <br />
<br />
Can you imagine comparing the difference
between a P3C (or even the P2K) against a frame that actually increases
in CxA with increasing yaw, which is actually fairly common? </div>
<br />Tom Anhalthttp://www.blogger.com/profile/08175472546482777614noreply@blogger.com4tag:blogger.com,1999:blog-6080071290235905056.post-1948850389274622682014-09-07T17:14:00.000-07:002014-09-08T18:03:44.558-07:00New Zipp Tangentes - Speed, Course, and SLSpeed - the Crr results<div abp="1229" class="separator" style="clear: both; text-align: center;">
<a abp="1230" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEibcqsB4-LDf0xayF8qVRXjkeXaFKWD9Ofz4iiW-gRG4a2Xn1Y1ea1y3EIDb4pc-92S2SEvW6GjArNQ5mAVJCP5EZOHLMNzdeoEUbIlGXqm8HaIlStSSCF7eGAFp3O2eFDxdYdw32qH5no/s1600/Tangente.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img abp="1231" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEibcqsB4-LDf0xayF8qVRXjkeXaFKWD9Ofz4iiW-gRG4a2Xn1Y1ea1y3EIDb4pc-92S2SEvW6GjArNQ5mAVJCP5EZOHLMNzdeoEUbIlGXqm8HaIlStSSCF7eGAFp3O2eFDxdYdw32qH5no/s1600/Tangente.jpg" height="333" width="400" /></a></div>
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A bit over a week ago, Zipp announced at Eurobike the release of their entirely new tire line; specifically, the Tangente Speed and Course clincher models (in 23C and 25C versions for both) along with the Tangente SLSpeed Tubular models (a 24C and a whopping 27C version). Below you'll find my roller testing results for these new tires. The Speed models are based on a 220tpi nylon casing and forgo an under the tread puncture belt, while the Course models use a 127tpi nylon casing and use puncture belt. The SLSpeed tubular models use a similar tread that is glued to a 320tpi cotton tubular casing with a latex tube inside and they also feature a puncture belt.</div>
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The previous Tangente models from Zipp were apparently very good from an aero standpoint. From a rolling resistance standpoint however, they were "less than stellar"...especially in this day of tire companies understanding the value of low Crr tires and their effect on performance and "comfort". So, one of the main drivers of this new tire development was in lowering the Crr of their tire offerings. On this point, I'd have to say that they've succeeded, in that Course models are basically tied with the current "industry standard" Continental GP4000S 23C from a Crr standpoint, with the Speed models being slightly faster. Their new tubular models, the Tangente SLSpeed, are also very low rolling resistance, with the 24C model basically tied with the benchmark Schwalbe IronMan Tubular, and the 27C (with the helping of its extra wide casing) taking over the current top spot for a "brand new" tire on the overall list of tires I've tested.</div>
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So, here's the nitty-gritty data for these tires, including data for the Schwalbe IM tubular, my "benchmark" GP4000S 23C tire, and the old model Tangente tubular. All of the clincher data for this round was performed on a Zipp Super 9 clincher disc, with the tubulars all tested on Zipp 900 tubular discs for consistency. In rank order from lowest Crr to highest:</div>
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Zipp Tangente SLSpeed 27C Tubular = .0028, 26W for pair @ 40kph, width = 26.8mm</div>
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Zipp Tangente Speed 25C Clincher = .0030, 28W for pair @ 40kph, width = 24.8mm</div>
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Zipp Tangente SLSpeed 24C Tubular = .0032, 29W for pair @ 40kph, width = 23.5mm</div>
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Schwalbe IronMan Tubular 22C = .0032, 30W for pair @ 40kph, width = 21.7mm</div>
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Zipp Tangente Speed 23C Clincher = .0033, 31W for pair @ 40kph, width = 23.8mm</div>
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Continental GP4000S 23C = .0034, 32W for pair @ 40kph, width = 24.8mm</div>
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Zipp Tangente Course 25C Clincher = .0035, 32W for pair @ 40kph, width = 24.7mm</div>
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Zipp Tangente Course 23C Clincher = .0035, 33W for pair @ 40kph, width = 23.8mm</div>
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Old Zipp Tangente 23C Tubular = .0045, 41W for pair @ 40kph, width = 22.4mm</div>
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<a abp="1251" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh-SKq65JFP1E8kUsDZ27itQYTGCKiHNNf3lfrH388Fr2pWdLbAOWSY1SghVBVc1QauCJ4XrNAshpE_KoCvaHbN2I301rYZLSxaDiVpA6A9lvHoa438riHi0Wb_MedesRu_0crBjqan4hc/s1600/Crr_bars.JPG" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img abp="1252" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh-SKq65JFP1E8kUsDZ27itQYTGCKiHNNf3lfrH388Fr2pWdLbAOWSY1SghVBVc1QauCJ4XrNAshpE_KoCvaHbN2I301rYZLSxaDiVpA6A9lvHoa438riHi0Wb_MedesRu_0crBjqan4hc/s1600/Crr_bars.JPG" height="235" width="640" /></a></div>
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So...what are the takeaways here? Well, I think it's fair to say that Zipp accomplished their goal of significantly improving the Crr of their tires, which can be easily seen by the comparison to the old Tangente tubular. Even the slowest of the new tires would save ~7W for a pair at 40kph, with the faster tires requiring more than 10W less at 40kph. That's significant. Also, in comparison to the GP4000S, the 25C Course model is basically tied with it, both in Crr and in actual tire width (at ~24.7mm) with the 23C Course model being only slightly slower (within the error margin of the testing). The 23C version of the Speed models tested out slightly faster than the GP4000S (again within the margin of error) but measures a full 1mm narrower when mounted on the same rim. That should help its aero properties. The 25C Speed model, however, is significantly lower Crr than the GP4000S saving a predicted 4W for a pair at 40kph, while measuring out at the identical width.</div>
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On the tubular front, the new 24C Tangente SLSpeed tire rolls just slightly better (within .0001 Crr) of the Schwalbe IronMan tubular, which is not surprising considering their similar construction (tread glued to a 320tpi cotton casing). The 27C Tangente SLSpeed tire rolls VERY fast, but its extra wide 26.8mm mounted width is going to result in an aero hit. I'd call that one a "rear use only"...but only as long as it can be shown that the width doesn't "give back" aerodynamically the gains that are made in Crr.</div>
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Well, that's the Crr results. What remains to be seen is how these tires perform aerodynamically. But, as I've said before, and we've seen recently with tires like the Specialized Turbo Cotton, low Crr can "make up for a lot of aerodynamic sins".</div>
Tom Anhalthttp://www.blogger.com/profile/08175472546482777614noreply@blogger.com16tag:blogger.com,1999:blog-6080071290235905056.post-73571160936904532952014-08-29T15:59:00.000-07:002014-08-29T15:59:26.578-07:00Some more Conti Crr dataI often get asked about how some of the other Continental tires roll, such as the Attack/Force models, and the 23C version of the SuperSonic tire. Well, thanks to Eric Reid (who sent me a new Attack and a slightly used Force) along with Thomas Gerlach (who sent me a VERY well used 23C SuperSonic) I know have a couple of those data points.<br />
<br />
To be clear on the SuperSonic, when I say very well used, I mean VERY well used...according to Thomas, this tire has ~600-1000 miles on it of rear tire used. When mounted on my Mavic Open Pro test rim and inflated to 120 psi, I measured a flat section on the tread that was a full 7mm across. In other words, it was near "end of life" ;-)<br />
<br />
So, without further ado, here are their results:<br />
<br />
Continental Supersonic 23C (WELL worn) = .0027, 25W for pair @ 40kph<br />
Continental Attack 22C = .0035, 32W for pair @ 40kph<br />
Continental Force 24C = .0029, 27W for pair @ 40kph<br />
<br />
By comparison, here's the results for the "benchmark" GP4000S:<br />
<br />
Continental GP4000S 23C = .0034, 31W for pair @ 40kph<br />
<br />
My suspicion is that a new 23C Supersonic would probably test out closer to .0030. The worn Crr result puts it currently at the top of my Crr chart, but with a hefty asterisk.<br />
<br />
The result for the Attack model shows it to roll about the same as (or just slightly worse than) the GP4000S, but with its narrower profile (22.7mm vs. 24.2mm) it should be slightly more aerodynamic. The Force model rolled very well, although it too had a small amount of miles on it. It basically put it in a tie, or slightly behind the top mark for a brand new tire I've tested, the Specialized Turbo Cotton. However, it also measured a fairly wide 25mm on my narrow test rim. On a wider rim, such as a Zipp Super9 disc, it would most likely measure as much as 26mm.<br />
<br />
The spreadsheet linked to in the upper right of this blog has been updated to include these results.<br />
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<br />Tom Anhalthttp://www.blogger.com/profile/08175472546482777614noreply@blogger.com2tag:blogger.com,1999:blog-6080071290235905056.post-77395228138401974632014-07-15T00:00:00.000-07:002014-07-15T00:02:48.273-07:00There's a new Sheriff in town...<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhDFTVfY5hfOUDZyOx1J8WYUe-ABPCIPdQQS2G7cb8nyEOVpBRM4hbSQ7q_vbB3wmZahVD7PvVb5Lsfv3pbRdVC_seSDmaEzQe0VnLgRaiDKY1qaZGmlFnBidVugVyHhgRU5icnhI5qy7w/s1600/2014-06-28+09.56.00.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhDFTVfY5hfOUDZyOx1J8WYUe-ABPCIPdQQS2G7cb8nyEOVpBRM4hbSQ7q_vbB3wmZahVD7PvVb5Lsfv3pbRdVC_seSDmaEzQe0VnLgRaiDKY1qaZGmlFnBidVugVyHhgRU5icnhI5qy7w/s1600/2014-06-28+09.56.00.jpg" height="300" width="400" /> </a></div>
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If you check the link to the overall Crr spreadsheet in the upper right of this blog, you'll see that there's a new top entry. It's the tire pictured above, the Specialized Turbo Cotton 24C which was introduced today. It sits firmly at the top of my list of production tires I've personally tested on the rollers, with a predicted on-road Crr of .0029, as compared to the Crr of .0031 for a trio of tires that used to be in a virtual tie (the Vittoria EVO Open Corsa Triathlon 22C, the Vittoria EVO Open Corsa Slick 23C, and the Schwalbe IronMan 22C Tubular).</div>
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The fact that it's so well rolling is not surprising considering it's construction. Like those other 3 tires, it's based on a 320tpi cotton casing. The main difference from those other tires is, of course, the tread that's glued onto it, which in this case is made from Specialized's proprietary Gripton material that they introduced last year with the S-Works Turbo tire. I've found this compound to truly live up to it's name, as can probably be guessed by the amount of wear on the labeling in the picture above.</div>
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OK...great...so it rolls really well (~4W less for a pair @40kph as compared to the "benchmark" Continental GP4000S) and rides/handles great, but is it aero? Or, at least "aero enough"? As I've written before, Crr can make up for a great deal of aerodynamic "sins" <a href="http://bikeblather.blogspot.com/2013/04/why-tire-crr-matters.html" target="_blank">http://bikeblather.blogspot.com/2013/04/why-tire-crr-matters.html</a> . Is the Turbo Cotton at least aero enough to take advantage of its ultra-low Crr to make it a good choice when aero is of a concern? Apparently...yes.</div>
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In interactions with the folks at Specialized, I was given a spreadsheet that shows the drag data for a test run taken with Zipp 404FC clinchers in a Venge road bike. The tires tested were the S-Works Turbo, the Turbo Cotton, and the Continental GP4000S 23C, which has been shown to have excellent aerodynamics on a variety of wheels. The plot of CdA vs. yaw angle is shown below:</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi-tFVjYRy3-ZhrYYC0LX9DSyEnNUzl7DRl-j-dD_yZKjXA5FINvOBlfj4XJZGoN-6TYoYLdK92pr0dD4eJWC_lbTc10J7juYlb0zzVVM9KGErm6Y-CSBGp3nOXytA3miM5DJDHLrP2JlY/s1600/CdAs.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi-tFVjYRy3-ZhrYYC0LX9DSyEnNUzl7DRl-j-dD_yZKjXA5FINvOBlfj4XJZGoN-6TYoYLdK92pr0dD4eJWC_lbTc10J7juYlb0zzVVM9KGErm6Y-CSBGp3nOXytA3miM5DJDHLrP2JlY/s1600/CdAs.JPG" height="368" width="640" /></a></div>
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As you can see, it shows that the Turbo Cotton is basically tied with the GP4000S at low yaw angles (up to 5deg), but then the GP4000S results in up to .010 m^2 lower CdA at 15deg of yaw. It's also interesting that the S-Works Turbo appears to be more aero than the Turbo Cotton. This could perhaps be because of the "lip" at the interface of the glued-on tread and the casing on the Turbo Cotton.</div>
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Another way of looking at this is by combining the Crr results with the aero results. Here's what the combined power would be for 40kph (85kg load). As can be seen, the low Crr certainly helps the Turbo Cotton beat the GP4000S all the way out to 10deg, while at 15deg of yaw the Conti actually beats it by ~3-5W. Above 15deg, the margin narrows again.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjmij1A8eA1hA1AcOTXRChEE8AWLcl2Y8YfLPkKMiwJJ8B0iWC_QXh8hqHxXga_iZy1XPauodRBDCWnd_13hyphenhyphen6In3vYNWVDrIvZ4xEBAt-tgIAoG_x0_h9P0v6meOgyV87GGdJe-af7cKk/s1600/Total+Power+vs+Yaw.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjmij1A8eA1hA1AcOTXRChEE8AWLcl2Y8YfLPkKMiwJJ8B0iWC_QXh8hqHxXga_iZy1XPauodRBDCWnd_13hyphenhyphen6In3vYNWVDrIvZ4xEBAt-tgIAoG_x0_h9P0v6meOgyV87GGdJe-af7cKk/s1600/Total+Power+vs+Yaw.JPG" height="452" width="640" /></a></div>
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Well...it's pretty fairly obvious what I would do with this right? Time to analyze the combined aero+rolling drag for a weighted average of yaw angle, like was done in the blog post I linked to above. In short, here's how that turned out (using the Crr from my own roller measurements):</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhjJazWP9HR3pBGL2mBdIkPzcQRCfnLKNBAKkFu0Nudqy5TWE3zGfVejNDrA7l_OG45bQDXXiaS58vBPJzpUTVpMszJ_qKapQ3DABU-Nt2Pt0aK_vY4_CzeK_2YCqkcq1LMWnwvloWnTaU/s1600/SW_Cotton_Drag.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhjJazWP9HR3pBGL2mBdIkPzcQRCfnLKNBAKkFu0Nudqy5TWE3zGfVejNDrA7l_OG45bQDXXiaS58vBPJzpUTVpMszJ_qKapQ3DABU-Nt2Pt0aK_vY4_CzeK_2YCqkcq1LMWnwvloWnTaU/s1600/SW_Cotton_Drag.JPG" height="380" width="640" /></a></div>
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What does that mean? Well, using the Mavic generated wind yaw angle weighting (as in the previous analyses), it shows that the excellent Crr of the Turbo Cotton tire overcomes the lesser aerodynamic performance at higher yaw angles (as compared to the GP4000S), at expected apparent wind speeds up to >50 kph. And it stays faster than the S-Works Turbo all the way up to apparent wind speeds of 60kph. Fairly impressive.</div>
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I've ridden a pair of these tires on my road bike for the past few weeks...and I have to admit that I've found my new favorite "all around" tire for racing. It's a no-brainer selection for road races and crits due to its naturally (because of the construction) good ride quality and cornering grip (because of the tread compound). I've yet to TT on these tires...but it's pretty tempting. They seem to work fairly well for Tony Martin for that purpose. Then again, I have a feeling Tony Martin's average apparent wind yaw angle is pretty darned low :-)</div>
Tom Anhalthttp://www.blogger.com/profile/08175472546482777614noreply@blogger.com3tag:blogger.com,1999:blog-6080071290235905056.post-67057774756060407492014-07-06T23:03:00.001-07:002014-07-06T23:13:04.858-07:00Crank Length? Whatever...(within reason)<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjboNBvZ-vYodYOp0DfZwUaq9oEFaDnRlJQSw-lv_TF0EEZhxUp84QWTR1PQBc_JmxGxTZ2-c3VWz3JikMDp_cX9XcZo9fX1ZiHQLC30SS-S4vykSrLPhCThO2oy4j94kglYOufdOkkQd0/s1600/zcranks.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjboNBvZ-vYodYOp0DfZwUaq9oEFaDnRlJQSw-lv_TF0EEZhxUp84QWTR1PQBc_JmxGxTZ2-c3VWz3JikMDp_cX9XcZo9fX1ZiHQLC30SS-S4vykSrLPhCThO2oy4j94kglYOufdOkkQd0/s1600/zcranks.jpg" height="400" width="375" /></a></div>
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Discussions about bicycle crank length have been a fairly hot subject recently. There's a trend in TT/Tri circles to use shorter than "normal" crank lengths. This is done to allow folks to either open up the distance between their torso and leg at the top of the pedal stroke (to be better able to produce power) and/or allow them to lower the angle of their torso relative to the ground in an attempt to get more aerodynamic. Sometimes it's done for both. One thing that is commonly brought up is questions about how using shorter (or longer) than normal cranks affects sustainable power output. Does it...or not?<br />
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There's a lot of data out there showing that wide variations in crank length do not have significant effects on power output, such as the work done by Jim Martin at the University of Utah, summarized here: <a href="http://www.plan2peak.com/files/32_article_JMartinCrankLengthPedalingTechnique.pdf">http://www.plan2peak.com/files/32_article_JMartinCrankLengthPedalingTechnique.pdf</a><br />
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From that presentation, "170mm cranks would compromise the power output of the shortest and tallest riders by AT MOST 0.5%. For example 6 watts out of 1200"<br />
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Another takeaway: "Crank length and pedaling rate influence metabolic cost and efficiency only by influencing pedal speed."<br />
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How can that be? Doesn't it logically make sense that for an optimum setup, a person needs a crank length proportional to their leg length? For example, there are websites out there that claim to identify the "ideal" crank length for a given person (<a href="http://www.nettally.com/palmk/crankset.html">http://www.nettally.com/palmk/crankset.html</a>). However, one thing that most folks miss on that site is that the lengths of cranks recommended with that method uses an underlying assumption with no apparent basis, i.e.<b> "The standard crank length of 170mm is optimum for a cyclist with a 31-inch inseam." </b>The entire method is anchored in that assumption...and yet, the Martin study summary I linked to above shows that power production is relatively unaffected over a wide range of crank lengths for a wide range of leg lengths. Is there an optimum? Perhaps...but, even if there is, the Martin data shows that varying from that optimum (even by relatively large amounts) doesn't appreciably affect power output.<big><big><br /></big></big><br />
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But, doesn't a shorter or longer crank affect your "leverage"? Sure...but that difference in leverage can be compensated for elsewhere in the drivetrain. The crank isn't the ONLY lever between your foot and the ground. The gears themselves, along with the rim and tire diameter are also "levers", which can be varied. One thing to keep in mind is that physiologically, our muscles have a preferred shortening speed, which results in a preferred foot speed at the pedal. I'm not talking about cadence...I'm talking about the tangential velocity that the foot travels at during the power production (i.e. downstroke) phase of the pedal cycle. <br />
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<u>The Challenge:</u><br />
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A little over a month ago, in a discussion on the Wattage Google Group about the effects of differing crank lengths, the following was posted in response to the idea that changing crank lengths could be "compensated" by varying gearing selections:<br />
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<i>"The gearing argument has been raised many times. It's usually raised and
argued a lot by people not on the big side of the spectrum, ie people
that are already on somewhat ideal cranks.<br /><br />My counter argument is this:<br /><br />If
you are riding say 170mm cranks and you firmly believe that gearing can
wholly make up for cranks of the wrong size. I encourage you to take
the "Pepsi Challenge" that challenge is this:<br /><br />1: Go TT up your
favorite 15 minute or longer hill at LT or greater power (by HILL I mean
something with average grade 6% or greater) with your current setup and
time it a few times. <br />2: Then put on crank arms that are only 87.5%
in length of your current setup. That would be 148.75mm if you are
currently riding 170s. You now have my proportional experience setup of
me riding 175mm cranks.<br /> Take your own medicine and re-gear
appropriately. Now ride that setup for a few weeks and go TT up your
favorite hill a few more times and time it. <br /><br />If you can show me you can do the same time with your medicinal gearing going full tilt, then I'll happily eat some humble pie.<br /><br /><br />I've
offered that challenge for a few years now, and suprisingly enough NO
ONE HAS TRIED IT. Go figure. News flash, I and many other long legged
people that have actually taken that "pepsi challenge", have come to the
very real conclusion the longer arms are faster. Now we can quibble
over why they are, but that's kinda irrelevant, fact is they are.<br /><br />So
I really challenge you or anyone else who is of normal size to take
that challenge and see what it's REALLY like to be riding something so
far out of what for what your body needs. Been over 5 years since I
first offered that challenge, and I'm still waiting for someone of
"normal" size to try it out...patiently.<br /><br />cheers,<br />-kieran"</i><br />
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<i><a href="https://groups.google.com/forum/#!msg/wattage/kVyNPWvOq7M/iNP0DIn-QWUJ">https://groups.google.com/forum/#!msg/wattage/kVyNPWvOq7M/iNP0DIn-QWUJ</a> </i><br />
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Not being one to shy away from a challenge like that...especially since the one doing the challenging is someone I know...I decided to take it up. Luckily, I have a friend (Greg Steele, of Beehive Bicycles in Salt Lake City <a href="http://www.beehivebicycles.com/">http://www.beehivebicycles.com/</a>) who let me borrow a set SRM cranks with the adjustable length option.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj_XZxmYA7gQB2Mr0zkc2gIf0IRNcgPv2mKIOR5TgASNn9NrJy5aK0HCUSIowK8YXXpYiyFF-4MGOYkHJNDjAlaHYHXiTvkO49g3LdK4Fay_UYUNzVynraHzPsWySX4jLA53w0l0SWcgKs/s1600/2014-06-21+12.15.51.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj_XZxmYA7gQB2Mr0zkc2gIf0IRNcgPv2mKIOR5TgASNn9NrJy5aK0HCUSIowK8YXXpYiyFF-4MGOYkHJNDjAlaHYHXiTvkO49g3LdK4Fay_UYUNzVynraHzPsWySX4jLA53w0l0SWcgKs/s1600/2014-06-21+12.15.51.jpg" height="400" width="300" /></a></div>
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These cranks allow for an adjustment range of 150-190mm. To do the testing, I decided to use the first 2 miles of a local ~8% average grade hill. From the Kirby Palm "method", I used as the first test a setting of 175mm since that's what his formula claims is the "optimum" for my 32" inseam (as measured per his instructions). In order to ensure that my lowest gearing was as equivalent as possible, I chose a 12-25 cassette for use the 175mm cranks. Since the crank length was pretty close to my normally used 170mm, all I did for adjustments was lower the saddle slightly. After setting everything up, off I went to the hill and give it "full stick" for my baseline. Here are the results:<br />
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Time = 12:50, Power = 289W, Cadence = 73 rpm, HR = 170bpm<br />
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For the short crank length, I wanted to use something that was equivalent, or below, the "87.5% below optimum" in the challenge above. For that, I chose 150mm, which is actually only 85.7% of the "optimum" 175mm length. In order to assure nearly equivalent low gearing, I chose a 12-30 cassette to pair with my 39T small ring.<br />
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Now then, when making such a large change in crank length, it's important to make sure to maintain the relationships between the saddle, the bars, and the foot during the "power", or downstroke part of the pedal cycle. As such, when I adjusted the crank length from 175mm down to 150mm, I did 2 things with the saddle. First, I raised the seatpost such that the distance between the portion of the saddle I rest my sitbones on and the pedal at max extension was the same distance, but I ALSO moved the saddle rearward on the rails so that in the end it was a full 25mm further rearward relative to the center of the BB than when the cranks were set at 175mm. This was done to keep the relationship between my lower leg and the pedal equivalent at the "3 O'clock" portion of the pedal stroke. Because of the movement in the saddle (both up and rearward), that also meant I need to move the bars the same directions to keep the bar to saddle relationship as close as possible. Luckily, I had a stem handy that was short enough, and with a high enough rise so that I could do this with a fairly simple stem swap. It wasn't the exact dimensions required, but it was close enough. Shown below is an overlay of the 2 setups.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh_v5afgVgCJtDQYLCszD5tc10pZXToBP4wsml9FJX6kgkgjTjHgxzfcTUV_BG4JqhqbuLBBYg0IrkVvXnq76C1v4lpls963vc65MbD9HmP7wkmu1TZy88ns0n6knBx405Z11QF28EeFqQ/s1600/150on175.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh_v5afgVgCJtDQYLCszD5tc10pZXToBP4wsml9FJX6kgkgjTjHgxzfcTUV_BG4JqhqbuLBBYg0IrkVvXnq76C1v4lpls963vc65MbD9HmP7wkmu1TZy88ns0n6knBx405Z11QF28EeFqQ/s1600/150on175.jpg" height="328" width="400" /></a></div>
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So...after making the setup change a few days after the baseline run, I then ventured out to the test hill and with the only "accomodation" being the ~15 minute ride over there, I did a run with the 150s. Here are the results for that:<br />
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Time = 12:50, Power = 286W, Cadence = 84 rpm, HR = 171bpm<br />
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Or...basically the SAME time, power, and HR as the 175mm crank length run. As expected, the cadence increased so that my tangential pedal speed and average pedal force were the same. This can be easily seen with a <a href="http://www.trainingandracingwithapowermeter.com/2010/04/other-quad_24.html" target="_blank">Quadrant Analysis</a> plot of each run. <br />
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175mm Crank QA</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjh1iNsW-3M11mINTkfUy_wjxYqLzEJ9fP2XjvpP2o2tPly1SawkUbtZlhXFIVg8AwkPGMgeALQHFk38nVpmljGfipZWU125Cq0hodxsuKbVzkqYWS3IRee-prNUsQwAYierDUQvijSHu8/s1600/QA175.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjh1iNsW-3M11mINTkfUy_wjxYqLzEJ9fP2XjvpP2o2tPly1SawkUbtZlhXFIVg8AwkPGMgeALQHFk38nVpmljGfipZWU125Cq0hodxsuKbVzkqYWS3IRee-prNUsQwAYierDUQvijSHu8/s1600/QA175.png" height="287" width="400" /></a></div>
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150mm Crank QA</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEikI8JV2Oi6ghqgqg8fdyeM58ATXgYTZOuYGR38S8c64F9tX0QJobrWyaRECECvR4ly6tDd4kOWycF5zYyyVFkD-PnlkWCdZThVr89oJlU8PcIRrTNy-8HE1HRwFFkgkS_qNLt01tq12T8/s1600/QA150.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEikI8JV2Oi6ghqgqg8fdyeM58ATXgYTZOuYGR38S8c64F9tX0QJobrWyaRECECvR4ly6tDd4kOWycF5zYyyVFkD-PnlkWCdZThVr89oJlU8PcIRrTNy-8HE1HRwFFkgkS_qNLt01tq12T8/s1600/QA150.png" height="286" width="400" /></a></div>
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Pretty much identical, no?</div>
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Anyway...so what does this all mean? It means that determining an "optimal" crank length for bicycling isn't very important. Instead of worrying about it from that standpoint, just understand that a wide range of lengths are acceptable, and use it as a "lever" (pun intended) for other things, such as fitting issues. One thing you might want to be wary of is going too large, in that that actually can start causing problems at the top of the pedal stroke and/or prevent the most aero position for a given event. It's somewhat hard to go "too small" (within reason) on crank length...just make sure you're geared adequately for the course profiles.</div>
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Oh...and it also means Kieran needs to eat some "humble pie"....nom, nom, nom ;-)</div>
Tom Anhalthttp://www.blogger.com/profile/08175472546482777614noreply@blogger.com25tag:blogger.com,1999:blog-6080071290235905056.post-57675381304068842492013-12-09T10:51:00.001-08:002013-12-09T10:51:42.212-08:00A Compendium of Tubeless Crr Results (plus getting up to date with some Vittoria and Specialized results)Well...it's been awhile since I posted. Sorry about that...but, after setting up a wheel for road tubeless as a part of the last post on the Schwalbe Ironman tires, I decided to try to get my hands on as many road tubeless tires as I could to see if there were any "gems" in the bunch. In the past, the road tubeless offerings all tended to have less than stellar Crr results (mostly due to the butyl air barrier layers applied), but the Schwalbe IM offering showed that there might be some road tubeless offerings finally getting their Crr down there. So, to start, here's how they stacked up, with a Continental GP4000S (latex tube) in there for comparison:<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjPKKFriFWJNUyb24O0HYg7KWsaq7AnDA7PhI0YrGwm6BlJXqY_FHMrVGCcvRvncXFC3HQoF2mBiRjTmTUt_zcH9UMUXXs-f4fLtfSHcS-3xfthlUAs12BASybknGS22L6nTJ0Wy8ENiDk/s1600/Tubeless+Crr.PNG" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjPKKFriFWJNUyb24O0HYg7KWsaq7AnDA7PhI0YrGwm6BlJXqY_FHMrVGCcvRvncXFC3HQoF2mBiRjTmTUt_zcH9UMUXXs-f4fLtfSHcS-3xfthlUAs12BASybknGS22L6nTJ0Wy8ENiDk/s640/Tubeless+Crr.PNG" width="627" /></a></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh5MAnzX3vBPSWKWWzfsLoKQcjS2ejQS0uhrKg0WnjkeiFIDokIE2Ku6OZ8f9j5uEAgDsa9LXddc0Z3h009yw0QUVfurTNFjbehbGUi6mJjD8AjYCcoZfr03Cz3MbToEAhDDlBufwJEc5s/s1600/Tubeless+Power.PNG" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh5MAnzX3vBPSWKWWzfsLoKQcjS2ejQS0uhrKg0WnjkeiFIDokIE2Ku6OZ8f9j5uEAgDsa9LXddc0Z3h009yw0QUVfurTNFjbehbGUi6mJjD8AjYCcoZfr03Cz3MbToEAhDDlBufwJEc5s/s640/Tubeless+Power.PNG" width="548" /></a></div>
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Now then, as you can see, some of those tires compare favorably to the "benchmark" Continental GP4000S, but I also think it's important to keep in mind the measured widths. In this case, all were measured on a Zipp 101 rim (internal bead width = 16.25 mm):<br />
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IRC Roadlite Tubeless 25C = 26.8mm<br />
Continental GP4000S 23C (latex tube) = 24.7mm<br />
Schwalbe IM Tubeless 22C = 23mm<br />
IRC Formula Pro Light Tubeless 23C = 24.6mm<br />
Hutchinson Galactik Tubeless 23C = 22.5mm<br />
Hutchinson Atom Tubeless 23C = 21.8mm<br />
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As you can see, the IRC Roadlite Tubeless 25C measures nearly 27mm across when mounted on the Zipp rim...that's HUGE. It makes for a great road/training tire, especially on the rear, and in fact that's what I've been using for that purpose for the last few months. For front tire usage, especially due to it's narrower width and aerodynamic features, the Schwalbe appears to be the best of the bunch. The Hutchinson tires are narrow, but their Crr values are not so great...plus, it was my experience that the Hutchinson tires were significantly more difficult to mount (tight beads) than the Schwalbe or IRC tires. As for the IRC Formula Pro Light...that one is a bit of an enigma for me. It's Crr is in the "decent" range (not great, but not horrible either) but it seems to be the most fragile of the bunch. I used it for a short time as a rear tire and quickly suffered punctures large enough to not allow the sealant to work...and I think there are better choices for front tires...so, I'm not sure where I would actually prefer using that tire. That's a bit disappointing really, because I think that it's unique latex based air barrier layer is the way to go for tubeless applications.<br />
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<u>Tubeless Thoughts</u><br />
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After having ridden and played around with road tubeless offerings over the last few months, I've come to the conclusion that the purported "advantages" of running tubeless tires (with sealant) in road applications are really only realized if the vast majority of your punctures are from relative small items (i.e. 1mm or less). Anything larger than that, and the air volume is too small and the pressures too large, for the sealant to effectively seal AND let you continue riding...with cuts or punctures larger than 1mm, you will most likely end up having to pull over and swap in a tube anyway. So, if most of your problems with flatting are due to things like goatheads or "michelin wires", then tubeless with sealant is a really good way to go. If you instead have problems with things like "pinch flats" (from hitting sharp edges or objects) you can actually get a significant improvement in performance just from using latex tubes and/or larger width tires. Sure, latex tubes take some unique setup considerations for reliable use, but they're really no more of a hassle than setting up a tubeless tire using sealant...and in some ways they're easier on a day to day basis.<br />
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<u>Vittoria and Specialized Results</u><br />
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Over the past few months, I've been testing some tires for Greg Kopecky and Slowtwitch.com for inclusion in some review articles he's written. An example is seen here (<a href="http://www.slowtwitch.com/Products/Things_that_Roll/Tires/Specialized_Road_Tires_2014_3982.html">http://www.slowtwitch.com/Products/Things_that_Roll/Tires/Specialized_Road_Tires_2014_3982.html</a>). Listed below are some additional tire results that I'm adding to the overall Crr spreadsheet linked to in the upper right of the blog.<br />
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<br />Tom Anhalthttp://www.blogger.com/profile/08175472546482777614noreply@blogger.com10tag:blogger.com,1999:blog-6080071290235905056.post-54953509266711738972013-08-30T14:59:00.000-07:002015-11-14T08:34:49.630-08:00Schwalbe Ironman Tires - A Clincher, A Tubeless, and A Tubular<div class="separator" style="clear: both; text-align: center;">
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<i>Update Note: Since the testing of these tires and the publishing of this post, it's come to my attention that Schwalbe has apparently discontinued using latex tubes within their tubular tires. As such, one should expect the tubular version of the IM tire to roll significantly slower than tested below; in the range of 2-4W slower per tire. The tire tested will now be listed in my spreadsheet summary as "Out of Print" - 14 Nov 2015</i><br />
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Earlier this year, Schwalbe announced a set of tires marketed towards the triathlon/TT crowd...in fact, they're branded with the Ironman logo, so it's not too hard to figure out the target market ;-)<br />
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Anyway, the interesting thing about this announcement was that it wasn't just a single tire, but actually 3 tires: a clincher, a tubeless, AND a tubular model. The design goal for this line of tires was to come up with the best combination of tire properties (i.e. Crr, aero, and durability) for going fast (and far) against the clock. For aero, the tires are sized at 22C and have a noticeable parabolic shape. Additionally, there's a pattern molded into the sides of the tire that is intended to act much like the boundary layer trip features we've seen on tires like the Mavic CXR offerings.<br />
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Luckily, I was able to get my hands on a set of these tires and was able to put them on the rollers to see how they do. Upon first inspection, the clincher and the tubeless tires appeared to be virtually identical, with the tubeless model appearing to have an extra layer molded to the inside (most likely an air barrier layer), so I expected the tubeless to roll slightly worse than the clincher model with a latex tube. The tubular model is actually a traditional style "sew up" (i.e. a casing with glued on tread, not a 1 piece vulcanized model) with what appears to be a fairly high TPI casing with the a tread cap glued on that looks and feels just like the clincher and tubeless models.<br />
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So...how did they roll? Here's the answers:<br />
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Schwalbe Ironman Tubular (22C) = .0031<br />
Schwalbe Ironman Tubeless (22C) = .0035<br />
Schwalbe Ironman Clincher (22C) = .0041<br />
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Interestingly enough, it appears that the tubeless version has LOWER Crr than the clincher, even with the clincher using a latex tube. I find that very curious...that means there must be something different about the compounding or the casing with the tubeless, because there's no way an added butyl air barrier layer should be lower loss than a latex inner tube. In fact, at the time of the testing, the Schwalbe Ironman tubeless model was the fastest rolling tubeless tire I had tested, or even as compared to the tubeless tires Al Morrison has tested in the past.<br />
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Curious about what some miles would do to the Crr on the tubeless model, I left it on my rear wheel for just over 300 miles and then retested with the result of:<br />
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Schwalbe Ironman Tubeless - w/335 miles = .0033<br />
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Now THAT is the fastest tubeless model tire I've tested to date (I've got a bunch of tubeless tires I've been testing and I'll post a "compendium" soon), and the only one close to it is significantly wider (25C vs. 22C).<br />
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But, the real eye-opener of the group was the tubular model. Obviously, we know that the type of tire construction used (high TPI casing, latex tube, etc.) makes for a fast rolling tire. But, to be able to pull that off with a relatively thick tread cap glued on means that there must be some "magic sauce" in the tread compound. Of course, the performance of that tire also begs the question of why they just don't make an "open tubular" version of the tire for the clincher market instead of the current clincher...<br />
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So, it appears that they've done a good job on the Crr front. The clincher is on par with tires like the Michelin Pro 4s, the tubeless is pretty fast (slightly faster or slower than a Conti GP4000S, depending on miles), and the tubular is smoking fast as well. If the aerodynamics comes close to other tire models, these tires would definitely be an intriguing option for TTs and triathlons, especially for folks who plan on going pretty fast and/or in low yaw conditions (because of the relative narrowness) .<br />
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Also, as one extra data point on latex vs. butyl, I tested the clincher with a butyl tube instead and here's how it rolled:<br />
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Schwalbe Ironman Clincher (22C) = .0046<br />
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Once again, this shows that a butyl tube "costs" ~3W per tire as compared to latex...just sayin' :-)<br />
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The latest overall charts:<br />
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<br />Tom Anhalthttp://www.blogger.com/profile/08175472546482777614noreply@blogger.com16tag:blogger.com,1999:blog-6080071290235905056.post-76569330349558525882013-08-10T18:00:00.001-07:002013-08-11T07:11:25.722-07:00Even more Crr results...and another example of why Crr matters, Mavic editionI did a short bit of roller testing yesterday. The main incentive for that was I was able to get my hands on a prototype set of the new Mavic CXR60C clincher wheels and I was itching to see how well the new CXR clincher tire rolls. Back in May I attended the press introduction for the CXR60 wheel line on behalf of <a href="http://slowtwitch.com/">Slowtwitch.com</a>. You can see my review of the wheels at that time here: <a href="http://www.slowtwitch.com/Products/Things_that_Roll/Race_Wheels/Mavic_unveils_Cosmic_CXR60__3624.html">Mavic CXR60 Intro</a>.<br />
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At the time of the press introduction, none of the attendees were able to ride the clincher version of the wheels, so a big question mark in my mind was how well the tires performed from a rolling resistance standpoint. From the wind tunnel results, obviously the wheel+tire system performed excellent in regards to aero drag, but I already had experience with the tubular CXR tires and found them to be slow...so much so that they basically "wasted" the aerodynamics. More on that later.<br />
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In any case, here's the results from yesterday's roller testing:<br />
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Mavic CXR clincher protoptype (23C) = .0036<br />
Challenge Triathlon clincher (23C) = .0034<br />
Challenge Triathlon w/Panaracer R'Air = .0042<br />
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Besides the Mavic tires (I tested 2 and they were nearly identical) I also tested a Challenge Triathlon clincher. Both the Mavic and the first run of the Challenge Triathlon were run with latex tubes, and then I decided to run the Challenge tire again after swapping out the latex tube for a Panaracer R'Air tube. This tube is a butyl based tube that is advertised to be compounded to be more flexible like a latex tube and I was curious to see if it made any difference in the rolling resistance. It did...but just barely (~1W for a pair @ 40 kph)...and that improvement is definitely not worth the cost of the tubes, especially considering one can get a latex tube for the same price.<br />
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The Mavic tire's Crr of .0036 is a very respectable result...much better than I was anticipating based on what I had measured for the tubular and what the Mavic engineers had claimed the difference was between the tires. By comparison, the average Crr I've measured for brand new Continental GP4000S tires is only slightly better at .0034, and is significantly better than the Michelin Pro4 Service Course Comps at .0041. Don't forget...for this testing (and the uncertainties involved) I consider anything within .0001 of Crr to be basically "tied".<br />
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At the end of the Slowtwitch.com article I linked to above, I had created a chart showing the combined affects of Crr and aero drag like I outlined in a previous blog post (<a href="http://bikeblather.blogspot.com/2013/04/why-tire-crr-matters.html">Why Crr Matters...</a>) Shown below is how that chart looks with the measured Crr for the CXR60C prototype tires.<br />
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It's fairly obvious from that chart that the CXR60C is the fastest wheel+tire system that Mavic makes. In fact, the difference for a single front wheel at an expected apparent wind velocity of 40 kph is on the order of 5-6W on average in favor of the CXR60C over both the CXR80 and the CXR60T tubular wheels.<br />
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The latest published version of the roller testing Crr spreadsheet can be found in the link at the upper right under "pages". <br />
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<br />Tom Anhalthttp://www.blogger.com/profile/08175472546482777614noreply@blogger.com7tag:blogger.com,1999:blog-6080071290235905056.post-83868501492865552352013-08-04T12:42:00.004-07:002013-08-04T14:37:27.856-07:00Aero Field Testing using the "Chung Method" - How sensitive can it be?<br />
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As some of you may know, I've been field testing bike stuff and positioning with a power meter for 4 or 5 years now. My method of choice is Robert Chung's "Virtual Elevation", or VE protocol, sometimes known as the "Chung Method". He has a great presentation on it here: <a href="http://anonymous.coward.free.fr/wattage/cda/indirect-cda.pdf">http://anonymous.coward.free.fr/wattage/cda/indirect-cda.pdf</a> . When I first read Robert's info, I wrote up a spreadsheet that I've used since then to analyze everything from position changes to tire air pressure effects. Of course, since I wrote that spreadsheet for my own use, it's not exactly the most "user friendly" (Hey, I know what I'm supposed to do, I wrote it! ;-)...but, don't worry, everyone else is in luck since Andy Froncioni (the main tech guy behind <a href="http://alphamantis.com/">Alphamantis</a> and the <a href="http://ero-sports.com/">ERO</a> facility that recently opened at the indoor track in Carson) added a version of the same calculations (called "Aerolab") to the freeware power meter analysis software, <a href="http://goldencheetah.org/">Golden Cheetah</a>.<br />
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So, the question with this type of testing usually comes down to just how sensitive can it really be...especially as compared to something like a wind tunnel? Admittedly, there are some limitations to this type of testing, the main one being (at present time) that the results are mostly limited to zero yaw conditions, but as we saw in one of my previous blog posts, the most common yaw angles a TT'er or triathlete encounters are usually centered around zero yaw. Using the tool to make evaluations at zero yaw still can hold a significant benefit for someone interested in improving/testing bicycle aerodynamics.<br />
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A couple years ago, Dr. Andrew Coggan published a blog post titled "<a href="http://www.trainingandracingwithapowermeter.com/2010/10/challenge-to-cycling-aerodynamicists.html">A Challenge to Cycling Aerodynamicists</a>" in which he described a field test he undertook to take up something he coined the "Tom Compton Challenge". In short, it's an effort using known geometric shapes to try to determine the "sensitivity" of the aerodynamic field testing method.<br />
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Well, last year I discovered that my preferred field testing venue for VE runs had suffered some "traffic rerouting" that had made it much less appealing for the purpose (part of that "discovery" occurred when Andy sent his test setup to me to try and the results from my first course were very mixed due to excess vehicle interference after the nearby roads had been modified). So, I started scouting around for an alternative course and luckily found one that is much closer to my home (I can ride there in just a few minutes) and that has laps that are significantly shorter than the old course (shorter laps = shorter test run time). Both of these courses are best described as a sort of "extended halfpipe", an "out and back" course having a U-shaped elevation profile that allows for turnarounds to be taken at low speeds and thus avoid braking. Since identifying the new course, and having done just a few tests on it, one thing I wanted to do was to repeat the type of testing that Andy did and attempt to characterize the potential "sensitivity" of the course using the VE method.<br />
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Using Andy's setup as a guide, I set about figuring out what sorts of objects I could use for the test. I took a quick trip to the nearby Michael's craft store and acquired some styrofoam spheres, 2", 3", and 4" in diameter.<br />
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In my garage I had an appropriate length of 1/2" diameter wooden dowel, and short work with a hand drill on the spheres and I had a setup that placed the spheres well out to the side where they should be in clear air while riding. Also shown in the pic above on the left is a small washer which I placed on the end of the dowel during the first run instead of a sphere. I did that to act as a "cap" and make it more likely that the flow over the end of the cylinder stayed perpendicular. Here's how the dowel and sphere setup looked after being zip-tied to the basebar of my TT bike.<br />
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The hole in each sphere ended up being a nice friction fit, so swapping between spheres was a very simple process. <br />
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All runs were recorded with my trusty old yellow-cap PT Pro wheel mounted on the rear, with a cover in place to turn it into a de facto disc. I prefer to use a PT for my aero field testing since it eliminates the uncertainty of variations in drivetrain resistance across the gearing, plus the PT's "coasting zero" feature allows me to have the power meter zero while soft-pedaling (i.e. turning the pedals slowly while freewheeling) down the descents of the course at least once per lap. That helps to minimize any power meter drift during the runs.<br />
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So, with the test rig sorted out, it was time to head out to the test course and do some runs! To minimize wind and traffic effects, I prefer to head out to the course early on a Saturday or Sunday morning...before the small neighborhood that the course road services begins to wake up and starts moving around. A couple weekends ago, I headed out on a Sunday morning and rode over to my test course in 5 minutes, taking a small musette bag with the spheres, a notebook, and a couple of small tools I might need. Starting at 6 am, I did the runs in the following order:<br />
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<li>Rod only (w/washer "endplate")</li>
<li>3" sphere</li>
<li>2" sphere</li>
<li>4" sphere</li>
</ol>
I mixed the runs up like that since I suspected that the "rod only" and 2" spheres may be close to the same measurement (part of the rod is covered up by the sphere) and I wanted to make sure there was a good separation between the cases. I actually didn't sit down and calculate out the expected differences in CdA beforehand. I wanted to first determine what the VE analysis showed as the differences from the baseline (run #1) and then see how close to the calculated values the VE runs were. I did this because the method I use for determining the CdA using VE is a visual "leveling" procedure, and so there's a bit of "judgement" involved in determining what value best "fits" the overall plot to being level, and I didn't want that judgement being affected by any predetermined knowledge of what the expected differences should be.<br />
<br />
Once I returned home, it was time to download the PT files into the computer and do the VE analysis. As I described above, although it can be done in GC's Aerolab feature, I prefer to use my own home-brewed spreadsheet, mostly because I find it easier to expand the vertical scale to get a better handle on the leveling procedure, but also because I've recently added a feature that varies the on-road Crr as a function of the ambient temperature. In order to use the spreadsheet, the following inputs are required:<br />
<ol>
<li> Total Mass - Easy to get just by stepping on a scale with bike in hand</li>
<li>Weather Conditions - this means air temp, dew point temp, and barometric pressure (to determine air density). Luckily, there's a personal weather station listed on <a href="http://www.wunderground.com/">Weather Underground</a> literally less than a block from my test course that has updates loaded every 5 minutes. Using that station also allows for a cross-check on ambient wind conditions to make sure it stayed calm during the test runs.</li>
<li>Assumed Crr - For this, I use a weighted average of the front and rear tire Crr that I've determined from roller testing. The spreadsheet then compensates for the expected Crr due to the difference in the test ambient temperature and the 20C temperature to which my Crr results are normalized.</li>
</ol>
As an example of the spreadsheet and what the VE profile plot ends up looking like, shown below is a snapshot of the first run from the testing:<br />
<br />
<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgI-SZ24-qsHEdhvvw9Kqcufu2CXcuPhRXvmR_9dXoPFZquNwnEc0zvYplLf7apxmLrjTfGUztwHoPyRHkXNNDiULapIGT1XOkZh15o3-axWnSx18fvnFbERSgaQjiRSz1kqeY-OUcLUY4/s1600/Run_1_snap.JPG" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="462" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgI-SZ24-qsHEdhvvw9Kqcufu2CXcuPhRXvmR_9dXoPFZquNwnEc0zvYplLf7apxmLrjTfGUztwHoPyRHkXNNDiULapIGT1XOkZh15o3-axWnSx18fvnFbERSgaQjiRSz1kqeY-OUcLUY4/s640/Run_1_snap.JPG" width="640" /></a></div>
<br />
OK then, let's get to the results. Using the procedure outlined above, my best determination for the measured CdA from the runs was as follows (in order that runs were performed):<br />
<ol>
<li>Rod only = .2484 m^2</li>
<li>3" sphere = .2498 m^2</li>
<li>2" sphere = .2486 m^2</li>
<li>4" sphere = .2510 m^2</li>
</ol>
Now, how does that compare to what should be expected for those shapes? To determine that, I made a spreadsheet that calculated the expected CdA changes based on the typical values of Cd (in the Re number range of interest) for a sphere and a cylinder (sphere = 0.47, cylinder = 1.17) and their respective cross-sectional areas based on my actual measurements. As mentioned above, when I compared the "rod only" run to the sphere runs, I had to subtract the portion of the rod that was covered by the cylinder from the CdA calculation. I then took those expected changes in CdA and added them to the measured CdA from the "rod only", or baseline run to determine the expected CdAs for the runs with the spheres. Here's how they compared:<br />
<br />
<u>Run # - Sphere</u> <u>Measured CdA (m^2)</u> <u>Calculated CdA (m^2)</u> <u>Difference (m^2)</u><br />
<br />
2. - 3" sphere .2498 .2501 .0003<br />
3. - 2" sphere .2486 .2488 .0002<br />
4. - 4" sphere .2510 .2518 .0008<br />
<br />
<br />
Another way of looking at it is the expected and measured differences from the baseline:<br />
<br />
<u>Run # - Sphere</u> <u>Meas. Diff. from Baseline(m^2)</u> <u>Calc. Diff. from Baseline (m^2)</u> <br />
<br />
2. - 3" sphere .0014 .0017<br />
3. - 2" sphere .0002 .0004<br />
4. - 4" sphere .0026 .0033<br />
<br />
<br />
One last way of looking at this is from the perspective of expected change from from the previous run. Here's how that worked out:<br />
<br />
<u>Run # - Sphere</u> <u>Meas. Diff. from Previous (m^2)</u> <u>Calc. Diff. from Previous (m^2)</u> <br />
<br />
2. - 3" sphere .0014 .0017<br />
3. - 2" sphere -.0012 -.0013<br />
4. - 4" sphere .0024 .0029<br />
<br />
Not bad, huh? I've always said that when using this technique I consider measurements that are within +/-.001 m^2 to be basically "tied", and the above appears to bear that assumption out as being fairly conservative. It also gives me confidence that with careful technique I should be able to <i>easily</i> detect CdA differences on the order of .003-.005 m^2 and greater.Tom Anhalthttp://www.blogger.com/profile/08175472546482777614noreply@blogger.com7tag:blogger.com,1999:blog-6080071290235905056.post-74539713329657516272013-04-19T19:04:00.000-07:002013-08-10T08:45:26.601-07:00More Continental GP4000S testing...including a 20C<br />
I recently had the opportunity to test additional 23C Continental GP4000S tires, along with a retesting of my original sample after having been ridden ~200 miles as a rear wheel. I figured this would help give a good indication of both the repeatability of the roller testing and also an idea of the consistency across different tires of the same models. Here's how it went:<br />
<br />
<ul>
<li>04/05/13 - New tire with ~20 miles of use - Crr = .00336</li>
<li>04/14/13 - Same tire after ~200 miles of use - Crr = .00343</li>
<li>04/14/13 - Tire used in Flo aero tests - Crr = .00344</li>
<li>04/17/13 - New tire, fresh out of box - Crr = .00334</li>
</ul>
<br />
So, across those 4 samples, we get an average of .00339 (I'd round to .0034, which happens to be the result and number of digits I report in the spreadsheet) and a standard deviation of .00005.<br />
<br />
If I'm doing my stats right, then this means there's a 99% confidence range of .0033-.0035.<br />
<br />
Granted, this is a fairly small sample set, but it matches pretty well with my "gut feel" that the measurements reported in my <a href="https://docs.google.com/spreadsheet/pub?key=0AuJYBb4ZA401dDZtY2JWMG42UVFqSm8ybjVURDM0eHc&output=html">Crr spreadsheet </a>should be considered to have a tolerance of around +/- .0001, and that tires listed within .0001 of each other are basically "tied".<br />
<br />
I also acquired 20C Continental GP4000 in the black color. My intention there was to first confirm that the black color GP4000 20C tires have the "Black Chili" tread compound (They do...it says so right on the package), and additionally to see how well it rolls. The idea was that since it has a similar shape and tread markings as the 23C tire, then it possibly would work as well aerodynamically on narrow rims as the 23C tire appears to do on the wider rims.<br />
<br />
The result? 20C Continental GP4000 (Black) - Crr = .0041<br />
<br />
That's basically the same as what I found the old 19C Bontrager AeroWing TT tire to exhibit (.0043), in which case, I think I'd still prefer the 20C Continental SuperSonic (Crr = .0034) tire for narrow rims, especially for front wheel uses. As we learned in my last blog post, it would take a LOT of aerodynamic advantage to make up for that much of a Crr difference.Tom Anhalthttp://www.blogger.com/profile/08175472546482777614noreply@blogger.com5tag:blogger.com,1999:blog-6080071290235905056.post-13696095478794978672013-04-08T19:42:00.002-07:002013-04-19T18:28:01.545-07:00Why Tire Crr matters...<i>...and why you need to look at BOTH the aero drag of a wheel/tire combination AND the tire rolling resistance to help determine what is "fastest" (i.e. Low Crr can make up for a lot of aero "sins")</i><br />
<br />
(<i>update 04/14/13: Added Michelin Pro4 Service Course to chart after roller testing. See chart and discussion below)</i><br />
<br />
<span style="font-weight: normal;">Five years ago, Damon Rinard (when he was working at Trek) made a <a href="http://forum.slowtwitch.com/gforum.cgi?post=1741343;search_string=zipp%20aero%20data;#1741343" target="_blank">post</a> to the Slowtwitch triathlon forum </span><span style="font-weight: normal;">where he described calculating a rough average of aero drag combined with rolling resistance. The data he used was from some wind tunnel testing he had done with various tires on the same rim (a Bontrager ACC - 50mm deep) and he combined this with the expected "on road" rolling resistance from roller testing. He did this because he found that different tires made a large difference in the aerodynamic drag of the wheel/tire system, and that simply choosing tires based on low rolling resistance OR low aero drag performance might not be the right approach. </span><br />
<br />
<span style="font-weight: normal;">I thought that was a neat approach and reverse engineered some of his data and expanded the idea to look at the effects of varying wind speed. In order to do so, I needed to scale the aero drag (taken at 30mph tunnel speed) to different apparent wind speeds using the ratio of V^2/(30mph^2) - since drag force varies with the square of wind velocity. That value was then summed with the rolling resistance force, which is constant, and then the total combined aero and rolling drag was plotted as a function of expected apparent wind speed. </span><br />
<span style="font-weight: normal;"></span><br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiPGMO8hRWs4FGxzadrnG_yUr-iwpZ9N7chiVl-F0_G8EjCT7eoB9OX6U9xzH6V3xv4hxcBA1mP1WorRdV2OT4WMgwdgaD7FLsGqwHycYU-Ok3wBoKas36624DL52yQ70UWd6ab74lMIRc/s1600/TireTotalDragL.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="272" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiPGMO8hRWs4FGxzadrnG_yUr-iwpZ9N7chiVl-F0_G8EjCT7eoB9OX6U9xzH6V3xv4hxcBA1mP1WorRdV2OT4WMgwdgaD7FLsGqwHycYU-Ok3wBoKas36624DL52yQ70UWd6ab74lMIRc/s400/TireTotalDragL.jpg" width="400" /></a></div>
<span style="font-weight: normal;"></span><br />
<span style="font-weight: normal;"></span><br />
<span style="font-weight: normal;"></span><br />
<span style="font-weight: normal;">Interestingly, when Trek/Bontrager released the R4 Aero tire a few years later (after Damon had left Trek to work for Vroomen/White Design) they included a plot very similar to the one I had created back in 2008:</span><br />
<br />
<span style="font-weight: normal;"><br /></span>
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://media.bontrager.com/images/spotlight/201206_r4_aero/r4_aero_total_drag_force.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="http://media.bontrager.com/images/spotlight/201206_r4_aero/r4_aero_total_drag_force.png" width="400" /></a></div>
<span style="font-weight: normal;"></span><br />
<span style="font-weight: normal;"></span><br />
<span style="font-weight: normal;">To use that chart, you need to have an idea of what your general "race speed" is going to be and then figure out what the maximum apparent wind speed (i.e. the vector sum of the ambient wind speed at wheel level and the bike ground speed) you'll encounter. Then you can see what the <i>average</i> total force you'll be expecting from a particular combination. Now then, that's talking about the retarding force...if you want to know the <i>power</i> required for the different combinations, or the power differences between combinations, then you need to multiply the drag force value by the ground speed to get the rate of doing work (i.e. power) on that total drag force. Make sense?</span><br />
<br />
<span style="font-weight: normal;">One of the main takeaways from that exercise above I got was that looking at JUST aero drag or JUST Crr wasn't telling the whole story. It's very easy to "waste" a wheel/tire combination's low aero drag by using a slow rolling tire...and vice versa. But, the other takeaway I got is that really low Crr can "make up" for a lot of less than ideal aero drag performance</span><br />
<br />
<span style="font-weight: normal;">Well, for the plot above, the aero drag component was taken as just a simple average of the 5, 10, and 15 degree yaw angle drags. After seeing the plot below last fall (taken from the Mavic material given out at the CXR80 tire/wheel system introduction), I realized this type of estimate could be updated using a weighted average instead of a straight average. The weighting would be from the expected % time spent at each yaw angle. Obviously, we want to choose a combination based on it's performance under the conditions we expect to mostly see in our races. If we don't see large yaw angles very often, it might not be worth it to worry about differences in performance at those higher yaw angles between the equipment choices we are contemplating.</span><br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgrZqomphoey5quNELqiz1K4otcpveR89tq4M1pMdaR3HGh_ZJG2ip3jt9mtlgiV1t5lJ7fhCseSGhFX0Ka2BS8EH2VRKWLBc6qlF5wrp5MbAgQaaa666Vm46LR37lNWTStpME5Kz3BpPQ/s1600/MavicWeighting.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="235" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgrZqomphoey5quNELqiz1K4otcpveR89tq4M1pMdaR3HGh_ZJG2ip3jt9mtlgiV1t5lJ7fhCseSGhFX0Ka2BS8EH2VRKWLBc6qlF5wrp5MbAgQaaa666Vm46LR37lNWTStpME5Kz3BpPQ/s400/MavicWeighting.JPG" width="400" /></a></div>
<br />
<span style="font-weight: normal;">According to Mavic, the data taken above is from actual measurements (they built a "wind vane" type rig and attached it to a bike) from a large number of rides under varying conditons and courses. Although it may not represent the actual yaw angle distribution for any one particular ride (those will likely be skewed one direction or the other, depending on the course and conditions) but it does represent what one would expect over a large number of rides. As such, it should be a good tool for determining a good "all around" wheel/tire system choice. </span><br />
<br />
<span style="font-weight: normal;">Now then, what we need to update things further is some good aero data showing the drags at various yaw angles for different tire/wheel combinations. It would be really helpful if the data happened to be for tires which I've already roller tested and have an idea of the predicted "on road" Crr.</span><br />
<br />
<span style="font-weight: normal;">Well, we're in luck. The guys at Flo wheels went to the A2 tunnel last week and did just that on their new Flo30 wheel. They tested the Michelin Pro4 Service Course, the Conti GP4000S, the Bontrager R4 Aero, and the Vittoria Open Corsa EVO Tri. The last 2 were tires that I actually loaned them after Chris Thornham had contacted me asking if I knew of a good place to find the Bontrager tires. I happened to have a nearly new one handy and also offered to loan one of my Vittoria tires as well. Here's the blog post describing their tunnel visit and the aero data they took: <a href="http://flocycling.blogspot.com/2013/04/flo-cycling-flo-30-wind-tunnel-results.html">Flo30 Aero</a></span><br />
<br />
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhfmqtKZFJb3BLbHu6zG7uh1WW7o0e5GGC0mUYVRyfgGUCO515LZm3PDkYua6xKPn6GSfr-Zw2oJx4_FN08sj2WbIiUdfjYZqzLxbwXUtDTSYZ-_w-3x9NH_s5V9sDcQOzAwnZ2QBf5ZqFk/s1600/Screen+Shot+2013-04-05+at+5.17.54+PM.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="302" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhfmqtKZFJb3BLbHu6zG7uh1WW7o0e5GGC0mUYVRyfgGUCO515LZm3PDkYua6xKPn6GSfr-Zw2oJx4_FN08sj2WbIiUdfjYZqzLxbwXUtDTSYZ-_w-3x9NH_s5V9sDcQOzAwnZ2QBf5ZqFk/s400/Screen+Shot+2013-04-05+at+5.17.54+PM.png" width="400" /></a>As can be seen in their data, the GP4000S was the clear winner aerodynamically, with the R4 Aero close behind it. The one tire that doesn't look too hot is the Vittoria. Although it stays fairly close to the other tires up to ~7.5 degrees of yaw angle, after that the drag goes way up. However, we know from my roller testing (<a href="http://bikeblather.blogspot.com/2013/04/more-roller-testing-results.html" target="_blank">Crr chart</a>) that it's Crr <i>is</i> slightly lower than the other 2 tires, so it <i>might</i> be able to make up for that, especially at lower yaw angles.<br />
<br />
<br />
So, let's take a look. What is shown below is the result of taking a weighted average (using the Mavic probabilities for the weighting) of the drag values reported for the 3 tires that I have Crr data on (I'm working on getting a Michelin to roller test as well) combined with the Crr of each tire. I've used the values of Newtons for the drag force (since it's an <i>actual</i> force unit, as opposed to grams) so that the drag force results can be simply multiplied by the expected ground speed (in meters/second) to quickly calculate the power (W). (If you want to convert the values to grams, then just divide by 9.81 m/s - gravity - and multiply by 1000)<br />
<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgQUuG71OBsFSStG7ArvgIM0RM2d413biOdDumwrCd3pxWvon2tq21uPylumLTkQSxTGpaDfzlkzCEECkf1a5u7AB3NBdlGImJ1upNutrGNBVxCy9ny_f0EG0vz54NdeNcCWt51GyZLSbU/s1600/Flo30_Tires.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="180" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgQUuG71OBsFSStG7ArvgIM0RM2d413biOdDumwrCd3pxWvon2tq21uPylumLTkQSxTGpaDfzlkzCEECkf1a5u7AB3NBdlGImJ1upNutrGNBVxCy9ny_f0EG0vz54NdeNcCWt51GyZLSbU/s400/Flo30_Tires.JPG" width="400" /></a></div>
<br />
<br />
(Note: the above chart assumes a wheel loading of 38kg and represents a single front wheel) <br />
<br />
There's some interesting things going on in that chart. To understand what's going on there, it's helpful to realize that the "steepness" of each curve is controlled by the aero drag (it varies with the square of the wind velocity), while where the line sits vertically in the chart is controlled by the rolling resistance values (a constant force).<br />
<br />
Despite the apparently poor showing of the Vittoria EVO Tri tire aerodynamically, at lower expected apparent wind speeds it actually performs slightly better than the other 2 tires shown; up until ~27 km/hr where it's curve crosses the GP4000S curve. As compared to the R4 Aero tire, that crossover doesn't happen until expected apparent wind speeds of ~35 km/hr. At the apparent wind speeds that I expect to see during my TT'ing (~45km/hr) the GP4000S is obviously the leader, with the R4 Aero in second, but the Vittoria still has a predicted <i>average</i> combined drag force that's only .21N higher than the GP4000S. At the expected ground speed of ~42km/hr (i.e. 11.7 m/s), that results in a total power difference of just 2.5W. That's really not a very large amount, especially considering how much worse the Vittoria appeared to perform aerodynamically.<br />
<br />
Now then, you might be asking "why is that?" Simply put, a lot of it has to do with the fact that the yaw angles where the largest differences in aero performance occur are also the yaw angles that are weighted less in the aero drag average due to their lower probability of being experienced. Another interesting thing is that the differences in Crr between the Vittoria tire and the other 2 isn't very large (all within .0004 of each other), but that's enough to overcome a seemingly significantly worse aero performance.<br />
<br />
So far we've been talking about this subject in terms of races like TTs and triathlon bike legs where the front wheel is seeing "free air"...but, what about other types of bike racing? Well, when you're in a group and drafting, the apparent wind speed is going to be lower, along with the fact that the yaw angle distribution will narrow as well...and thus, that makes the Crr component all that more important. If you ever find yourself in the situation of riding up a false flat in a group while using poor rolling tires, you'll understand what I'm talking about here. Rolling resistance is actually a higher priority than wheel aerodynamics in road racing, in my humble opinion.<br />
<br />
For one last plot, I took the data from the rest of the Flo wheels that were subsequently tested with the GP4000S tire. That plot is shown below, and as expected at lower expected apparent wind speeds, the wheels are closer together in performance than with higher expected apparent wind speed.<br />
<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjh6uPhEtuaQYe3BOvoiZ_Hvob1jAUe__wPWoJ7qGaeE7bTVR8JiX0U3c5malxYclenhMPuZgDSju2i5s45IHdcBFG0Tb9kR4jvK2KT3PUg-LxUgvSGh1lkatJ-3mmi4FB0opjNM0LoQA4/s1600/FloWheels.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="175" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjh6uPhEtuaQYe3BOvoiZ_Hvob1jAUe__wPWoJ7qGaeE7bTVR8JiX0U3c5malxYclenhMPuZgDSju2i5s45IHdcBFG0Tb9kR4jvK2KT3PUg-LxUgvSGh1lkatJ-3mmi4FB0opjNM0LoQA4/s400/FloWheels.JPG" width="400" /></a></div>
<br />
<br />
There we are...I hope that helps to understand some of the tradeoffs involved with choosing tires and wheels for cycling. Of course, there are other properties further involved in these sorts of tradeoffs, such as durability and "grip", but those other properties are tough to combine into a chart like the above...and so are left up to the user to weigh separately.<br />
<br />
<i>Update 04/14/13:</i><br />
<i>The guys at Flo were nice enough to send me the Michelin Pro4 Service Course tire used in the aero testing above and so I got a chance to run it on the rollers. The resultant Crr was .0043. They also sent the Continental GP4000S used in their testing and it rolled identically to my own version of that tire at .0034. Using that, I was able to update the Total Drag Force chart to include the Michelin on the Flo 30. The interesting thing about the curve for the Michelin is that despite it's aerodynamics being fairly close to the GP4000S and the Bontrager R4 Aero (especially with the yaw weighting) on the Total Drag Force chart it NEVER overcomes the "hit" it takes on rolling resistance, even out to expected apparent wind speeds of 60kph. Once again, the importance of Crr comes to the fore...</i><br />
<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjn6RBloL-z0rZDwCXVlqZWACssczrl86LW_RGI2N7cqzWS3aPzxYfGsMz8R7tXPjYAiC88mSCT-rcnYh3fCLk4zUrMUBH5MQpkeWBRAmULP7bLJLyJAwAt5lqyPgTP-aay_5ltUhb4TZk/s1600/Flo30_Tires_wMPr4SC.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="165" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjn6RBloL-z0rZDwCXVlqZWACssczrl86LW_RGI2N7cqzWS3aPzxYfGsMz8R7tXPjYAiC88mSCT-rcnYh3fCLk4zUrMUBH5MQpkeWBRAmULP7bLJLyJAwAt5lqyPgTP-aay_5ltUhb4TZk/s400/Flo30_Tires_wMPr4SC.JPG" width="400" /></a></div>
<i> </i> Tom Anhalthttp://www.blogger.com/profile/08175472546482777614noreply@blogger.com16tag:blogger.com,1999:blog-6080071290235905056.post-36370884222771136952013-04-05T16:12:00.001-07:002013-08-10T08:43:32.639-07:00More Roller Testing ResultsWell, I happened to recently acquire a Continental GP4000S tire for a very reasonable price, and in light of the recent Flo aero testing, I decided it would be a good time to throw it on the rollers and see how it does. I also had a couple of well used "training/all condition" tires a friend loaned me so I tested those as well. Wow...some of those training tires REALLY sap the power!<br />
<br />
Anyway, here's the predicted on-road Crr for the 3 tires I tested today:<br />
<br />
Continental GP4000S 23C = .0034<br />
Specialized All Condition Pro II 23C = .0062<br />
Specialized All Condition Armadillo Reflect 25C = .0077<br />
<br />
The overall Crr chart now looks like this:<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhyy7YKMhHr6RFqLmtw4VEtOmBp8nUqDO_ttOlF0iRDtN1tzd1ik8lgHn85PNs5BzECC2cK-4sP_JxGAT5y9cpmDhfDO0k5BV7FR2eTsyra6uoLiXA0txVwBjDS-CMwEqntX2lduxpzHX8/s1600/TireCrr.JPG" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="411" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhyy7YKMhHr6RFqLmtw4VEtOmBp8nUqDO_ttOlF0iRDtN1tzd1ik8lgHn85PNs5BzECC2cK-4sP_JxGAT5y9cpmDhfDO0k5BV7FR2eTsyra6uoLiXA0txVwBjDS-CMwEqntX2lduxpzHX8/s640/TireCrr.JPG" width="640" /></a></div>
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<a href="http://www.blogger.com/blogger.g?blogID=6080071290235905056" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a><a href="http://www.blogger.com/blogger.g?blogID=6080071290235905056" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a>And here is the predicted power for 2 tires at 40kph (85kg total load):<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh175ivi0-wlRZf4Jy9dtCsCInKgn3mbF1JuGEYwHhTOJaPCCU0h-O8Thg34cQMOppqUCtnypjVC54ETbVc0geNfRz_4VqIs8RIf6AipqRm1dqAVsJFEy64qDbxRKpm1rO_Cs233Z8EvlA/s1600/TirePower.JPG" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="489" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh175ivi0-wlRZf4Jy9dtCsCInKgn3mbF1JuGEYwHhTOJaPCCU0h-O8Thg34cQMOppqUCtnypjVC54ETbVc0geNfRz_4VqIs8RIf6AipqRm1dqAVsJFEy64qDbxRKpm1rO_Cs233Z8EvlA/s640/TirePower.JPG" width="640" /></a></div>
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As always, the entire spreadsheet is saved here: <span style="font-family: Verdana, sans-serif;"><span style="font-size: x-small;"><span style="font-size: small;"><a href="https://docs.google.com/spreadsheet/pub?key=0AuJYBb4ZA401dDZtY2JWMG42UVFqSm8ybjVURDM0eHc&output=html" target="_blank">Crr Spreadsheet</a></span></span></span><br />
<br />Tom Anhalthttp://www.blogger.com/profile/08175472546482777614noreply@blogger.com16tag:blogger.com,1999:blog-6080071290235905056.post-21930517612717768942013-02-19T15:37:00.000-08:002013-08-10T08:42:37.411-07:00Tire Crr Testing on Rollers - The Chart..and a "how to"<div class="separator" style="clear: both; text-align: center;">
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiSZjoMctAxc3M7ETMs39jJveVryHZIkAjLThwu4JmlJFI86dA1WxPBxt6YBg7XZVJvd9-1dlLn-ZqHxNBSjCVrar-DFg_p5PvaqevMarMREEpBZKm0sF_66D7NE9N6GLgf6yt1dJEUfbM/s1600/2013-02-16+16.58.04.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiSZjoMctAxc3M7ETMs39jJveVryHZIkAjLThwu4JmlJFI86dA1WxPBxt6YBg7XZVJvd9-1dlLn-ZqHxNBSjCVrar-DFg_p5PvaqevMarMREEpBZKm0sF_66D7NE9N6GLgf6yt1dJEUfbM/s400/2013-02-16+16.58.04.jpg" width="400" /></a></div>
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<span style="font-family: Verdana, sans-serif;">In my last post I outlined the "<a href="http://bikeblather.blogspot.com/2013/02/tire-crr-testing-on-rollers-math.html" target="_blank">math behind the madness</a>" of testing the rolling resistance of bike tires on home rollers. In this one, I'll be showing the results of some of that testing I've personally done over the past year or so. I'll also go through a few tips and tricks I've learned in doing this sort of testing...just in case anyone else is crazy enough to try some of this potentially mind numbing testing.</span><br />
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<span style="font-family: Verdana, sans-serif;">OK, I know a few of you are out there are "champing at the bit" to see the results, so without any further ado, here's a chart showing my estimates for the power to roll a pair of various tires I've tested (on a "real road" and for an 85kg bike plus rider mass):</span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjgDiXGUsIpfGVHZQO_6yXhJ8cPzl9kIILWSPok-msHgzk9f_8Y7Y2u9ILpcRrEUkqPp31Fd5Q16It8CMTtVEpLgBeeDh67GisBRssKaNCbKFzL9alm7DwQfBn5NjTSznlyWKH3Cs0M6P8/s1600/TirePower.JPG" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="443" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjgDiXGUsIpfGVHZQO_6yXhJ8cPzl9kIILWSPok-msHgzk9f_8Y7Y2u9ILpcRrEUkqPp31Fd5Q16It8CMTtVEpLgBeeDh67GisBRssKaNCbKFzL9alm7DwQfBn5NjTSznlyWKH3Cs0M6P8/s640/TirePower.JPG" width="640" /></a></div>
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<span style="font-family: Verdana, sans-serif;">Here's the same chart, but showing the estimated "on road" Crr values:</span></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjEqVGQSnJxfjVlk9nZmG8PdymKfXAMoZzCwWGxLmkAN6RPPCEU73fc-Yl5mlZnCfHO7dQBYN3idY9fmz1yWvChd82n4zd8yBRyKiZkw4FaZ7m7gEwsaP4MTJNu4XIMLMnnfXqK8VoRzlg/s1600/Crr+Chart.JPG" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="377" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjEqVGQSnJxfjVlk9nZmG8PdymKfXAMoZzCwWGxLmkAN6RPPCEU73fc-Yl5mlZnCfHO7dQBYN3idY9fmz1yWvChd82n4zd8yBRyKiZkw4FaZ7m7gEwsaP4MTJNu4XIMLMnnfXqK8VoRzlg/s640/Crr+Chart.JPG" width="640" /></a></div>
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<span style="font-family: Verdana, sans-serif;">As can be seen, that's a fairly wide range of power requirements. The wrong tire choice can easily "cost" a rider 10-15W of power to go a given speed. When choosing tires, I commonly think of a scene from "Indiana Jones and the Last Crusade" where the Templar Knight guarding the Holy Grail says "...you must choose, but choose wisely...". After all, when you're done with a race and you lose by seconds, or inches...you would hate to have the following be said about your tire choice:</span></div>
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<span style="font-family: Verdana, sans-serif;"><u><b>The Setup:</b></u></span></div>
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<span style="font-family: Verdana, sans-serif;">OK, now that we've got that all out of the way, I thought I'd describe a bit about the setup I use for doing this sort of testing. As you can see in the pic at the top of this blog post, it's a fairly simple affair consisting of a set of 4.5" diameter Kreitler rollers, a front fork stand, and a bike equipped with a power meter (and a power meter head unit). That's really basically it. A couple of other pieces of equipment that are crucial for getting consistent results, in my experience, are:</span></div>
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<li><span style="font-family: Verdana, sans-serif;">A means to measure ambient temperature</span></li>
<li><span style="font-family: Verdana, sans-serif;">A means to measure rear wheel load</span></li>
<li><span style="font-family: Verdana, sans-serif;">A separate speed sensor and magnet (NOT on the wheel, but on the roller - see below) </span></li>
<li><span style="font-family: Verdana, sans-serif;">A notebook and pen</span></li>
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<span style="font-family: Verdana, sans-serif;">For measuring the ambient air temps during the test, I use my trusty Brunton ADC Summit, which I place at about axle level somewhere near the side of the rear wheel of the bike during the testing.</span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjsyHTB3-yGdD2CZUqB0LOan5Mv1sQ2dGhv6eqbN7pnYCkUKcnOvvjUhODboCvXKznnAl-74V7qCD91YvoDspO_TZuZIR5Jts4eiZ2CPCxvuYSm0NuZruJwbPVqd3Y_E09zvHI_ZzmBvuQ/s1600/2013-02-01+12.02.59.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjsyHTB3-yGdD2CZUqB0LOan5Mv1sQ2dGhv6eqbN7pnYCkUKcnOvvjUhODboCvXKznnAl-74V7qCD91YvoDspO_TZuZIR5Jts4eiZ2CPCxvuYSm0NuZruJwbPVqd3Y_E09zvHI_ZzmBvuQ/s400/2013-02-01+12.02.59.jpg" width="300" /></a></div>
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<span style="font-family: Verdana, sans-serif;">To measure the rear wheel load of the setup, I actually just use a digital bathroom scale which I've checked against known weights and typically is within 0.5 lbs of the actual weight. In order to make that rear wheel load measurement, I mount the fork in the fork stand, and in stead of placing the rear wheel on the rollers, I stack the scale on top of some wood scraps and place the rear tire on the scale. I stack it so that the rear axle is the same height off the ground as it would be on the rollers. As it turns out, a couple of scrap pieces of 3" square wooden post and the thickness of my scale put that measurement to within 1/4" of what it is on the rollers. Perfect.</span><br />
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<span style="font-family: Verdana, sans-serif;">Now then, let's talk about the speed sensor I mentioned above. One of the most important things to get an accurate measure of in this testing is the actual "ground speed" during the test. This can be done with a wheel mounted magnet and speed sensor, BUT that requires determining and changing the wheel rollout number for EACH tire tested. In my experience, that can be a bit problematic...especially due to the curved contact patch that is present on the rollers. It's very hard to get an accurate and consistent measure of wheel rollout that way. To solve that problem, I realized that instead of triggering a speed sensor on the wheel, I could instead attach a magnet to the end of one of the rear drums and then use a speed sensor triggering off of the drum. All I needed to do was to carefully measure the diameter of the metal drum (which will NOT be changing from test to test) and use THAT as the ground speed measurement for the testing. Here's what that looks like:</span><br />
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<span style="font-family: Verdana, sans-serif;">That's just a small rare-earth magnet attached to the end cap of the roller with double-sided tape, and a Garmin ANT+ speed/cadence sensor taped to the roller frame.</span></div>
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<span style="font-family: Verdana, sans-serif;">Lastly, the notebook and pen are where I write down the date, what tire I'm testing, the size, the ambient temps during the testing, the power meter zero offset numbers, and the actual measured tire width as mounted.</span><br />
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<span style="font-family: Verdana, sans-serif;"><u><b>The Protocol:</b></u></span><br />
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<span style="font-family: Verdana, sans-serif;">Alright, so everything is set up and we've gathered all the stuff needed. What's next? How do I do this? Well, here's a quick rundown of how I go about doing a tire Crr test (in "10 easy steps"!) This isn't the <i>only</i> way to do it, but it's how I've settled on things after doing this testing for a while:</span><br />
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<li><span style="font-family: Verdana, sans-serif;"><i>Mount the tire on the test wheel - </i><span style="font-size: x-small;">Most of my testing is done with my old yellow-cap PT wheel with a Mavic Open Pro rim. I started out testing with this wheel in order to get both a hub and crank power to determine the level of typical drivetrain losses in the setup. I wanted to know that for the occasions when I would be testing tires (such as tubulars) which I couldn't mount to the clincher PT wheel. Since I'm mainly interested in tires for time trials and road racing, I'll test them using a latex inner tube. Testing by others has shown that using a butyl tube can cause 10-15% higher Crr than with latex. </span></span></li>
<li><span style="font-family: Verdana, sans-serif;"><i>Pump the tire to the test pressure -</i> <span style="font-size: x-small;">What pressure to use is really up to you. I chose to do all of my testing with 120psi. The reason I chose that value was mainly so that I could compare my results more easily to the results of others, most notably the testing done by Al Morrison. Understand that on a perfectly smooth surface, the higher the pressure you pump tire up to, the lower the measured power requirements will be...however, that will only be true on the rollers, or on flat surfaces that are just as smooth. On "real roads", i.e. roads with typical roughness, that isn't necessarily the case and there will tend to be a pressure above which higher pressures actually will make you slower overall. Anyway, the key here is to pick a pressure and stick with it through your testing so that you are comparing tires on an equivalent basis. <span style="font-size: x-small;"> </span></span></span></li>
<li><span style="font-family: Verdana, sans-serif;"><span style="font-size: x-small;"><span style="font-size: x-small;"><i><span style="font-size: small;"><span style="font-size: small;">P</span>lace the wheel in the test bike<span style="font-size: small;"> - </span></span></i><span style="font-size: x-small;">Install the rear wheel in the test bike and place the chain in the chosen gear for the testing. I do my testing in a 53x13 gear for consistency. If it<span style="font-size: x-small;">'s not in there already, install the fork into the fork mount.</span></span></span></span></span></li>
<li><span style="font-family: Verdana, sans-serif;"><i>Measure the rear wheel load -</i> <span style="font-size: x-small;">This is done how I described above. I'll usually only do this once during a session, and for me I've found it's typically within a pound or two each time (my body weight tends to be fairly stable). This doesn't seem to be a super-critical measurement either, since a 1 or 2 lb. difference will only result in ~1-2% error in the final calculation.</span></span></li>
<li><span style="font-family: Verdana, sans-serif;"><i>Place rollers under rear wheel - </i><span style="font-size: x-small;">At this point, move the scale out from under the rear wheel and slide in the rollers. To get a consistent placement of the rear wheel on the rollers, I'll lift the fork mount slightly off the ground while I allow the rear wheel to spin as it touches the 2 rollers and then I carefully place the fork mount on the ground.</span></span></li>
<li><span style="font-family: Verdana, sans-serif;"><i>Climb on board - </i><span style="font-size: x-small;">It's now time to saddle up. I usually approach the bike from the non-drive side and put my left foot on the pedal and then carefully swing my right leg over taking care not to disturb anything in the setup. I'll then spin the cranks to make sure the PM is awake and the speed reading is working, at which point I'll clip out and zero the PM through the head unit. I'll note the offset value (from my Quarq) in the notebook along with the ambient temperature. </span></span></li>
<li><span style="font-family: Verdana, sans-serif;"><i>Tire warmup -</i> <span style="font-size: x-small;">Now it's time to warm up the tire to working temperature. Since my tests are done at 90 rpm (I find it's easier to hold a consistent rpm rather than focusing on the wheel speed) I'll warm up the tire at 95 rpm for 5 minutes. At the end of the 5 minutes, I'll stop and quickly check the PM zero offset and write the value down in my notebook along with the ambient temperature reading.</span></span></li>
<li><span style="font-family: Verdana, sans-serif;"><i>The Test - </i><span style="font-size: x-small;">Now it's time for the test. I'll bring the cadence up to 90 rpms and once that is steady, I'll start a 4 minute interval in the PM head unit. I'll concentrate on keeping a steady cadence through the whole interval, trying to be especially steady through the final 2 minutes since that is the section of the data I take the average power and ground speed from. At the end of the 4 minute test interval, I'll again note the PM offset (to make sure it hasn't moved appreciably during the test for some reason) and write down the ambient test. That's it. Test over...either I stop there, or if I have more to tires to test, I'll start back at step one (skipping the load measurement for repeat tests) and on through the remaining steps.</span></span></li>
<li><span style="font-family: Verdana, sans-serif;"><i>Download Data -</i> <span style="font-size: x-small;">Now it's time to get the average power and ground speed values from the head unit. I'll typically load the file into Golden Cheetah and then highlight the final 2 minutes of each test session and read off the averages as calculated.</span></span></li>
<li><span style="font-family: Verdana, sans-serif;"><i>Calculate the Crr -</i> <span style="font-size: x-small;">The final step is to take the average power and speed values, along with the wheel load and ambient temperature taken at the end of the test interval into a spreadsheet I've written to quickly do the calculations. I've loaded the spreadsheet onto Google Drive and it can be accessed here: <span style="font-size: small;"><a href="https://docs.google.com/spreadsheet/pub?key=0AuJYBb4ZA401dDZtY2JWMG42UVFqSm8ybjVURDM0eHc&output=html" target="_blank">Crr Spreadsheet</a></span></span></span></li>
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<span style="font-family: Verdana, sans-serif;"><u><b>Other Notes:</b></u></span><br />
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<li><span style="font-family: Verdana, sans-serif;">After doing a number of runs using both the crank-based power meter and the PT wheel, I was consistently finding that for the gearing chosen and the lower power levels (typically 50-100W) seen on the 4.5" rollers, the drivetrain losses were on the order of 5%. That's the value I enter in the spreadsheet.</span></li>
<li><span style="font-family: Verdana, sans-serif;">I did a fair number of runs with the exact same tire and at different ambient temperatures to determine what I should use as the temperature compensation value. In my case, I found it to be ~1.36% change per deg C (lower Crr with higher temperatures). Here's the plot of those tests:</span></li>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhLZrUzptePrtrfWnjLn26TtMnZf9tmdsRjXKyX2TE8g_jwReUnaiZJFv-GSZIkD8c9Lnfpx_TUYKBz5q1XMsfNOLPbTMW7Rhix0R7WjEZ84-piKh0Bh0a8IQ4uwlOp5KTT5YGJRLMEFwY/s1600/tiretempchart.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhLZrUzptePrtrfWnjLn26TtMnZf9tmdsRjXKyX2TE8g_jwReUnaiZJFv-GSZIkD8c9Lnfpx_TUYKBz5q1XMsfNOLPbTMW7Rhix0R7WjEZ84-piKh0Bh0a8IQ4uwlOp5KTT5YGJRLMEFwY/s400/tiretempchart.JPG" width="400" /></a></div>
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<li><span style="font-family: Verdana, sans-serif;">I normalize the Crr values to 20C. If you want to know what the Crr would be at various temperatures, you can just enter those temperatures into the appropriate cell on the first sheet of the spreadsheet.</span></li>
<li><i><span style="font-family: Verdana;">Added 2/19/12 - I realized I forgot to point out that I use a "smooth to real road" factor of 1.5X to account for the higher energy dissipation requirements of typical road roughness. This value is based on comparisons of roller based Crr measurements ("translated" to flat surface) and actual "on road" Crr derived from field tests and other means (i.e. iAero coast down values) for the same tires.</span></i></li>
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<span style="font-family: Verdana, sans-serif;">Well...that's about all I can think of for now. Hopefully that will help encourage others to give this a try. It's really not that difficult to do and is a good way to help you to "choose wisely" when it comes to tires for your "go fast" bike setup. </span>Tom Anhalthttp://www.blogger.com/profile/08175472546482777614noreply@blogger.com23tag:blogger.com,1999:blog-6080071290235905056.post-51299739600587433722013-02-09T21:07:00.000-08:002013-02-19T15:43:41.181-08:00Tire Crr testing on Rollers - The Math<br />
<span style="font-family: Verdana,sans-serif;">I've been doing a little bit of tire testing lately. But, before I reveal any results, I thought it would be good to go over some math. I know, I know...(I can hear the groans already), but I think it's important to review so people understand why it's reasonable to equate power to move a tire on a roller to power on flat ground. </span><br />
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<span style="font-family: Verdana,sans-serif;">It's long been known that bicycle rollers act as a sort of rolling resistance "amplifier". In other words, the differences in the rolling resistance between tires is magnified when riding on the rollers. It's usually a fairly subtle thing to try to "feel" the difference in rolling resistance in tires when riding outside, but it's pretty easy to tell the fast tires from the slow tires on rollers just by the exaggerated effort it takes. But, the question has long been "how much" of an amplifier are they? Well, back in 2006 I was discussing this with a few folks and realized that the equations to make that comparison between rollers and a flat surface Crr (Coefficient of rolling resistance) were already available...they just needed to be combined. Then, it was pointed out to me that the particular geometry of a typical roller setup needed to be accounted for as well. The normal "dual roller" setup on the rear of a roller set results in a geometric effect that actually increases the normal force on each roller. In other words, you can't just take the rear wheel load as if it was a single roller. So, I added that to the equations as well.</span><br />
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<span style="font-family: Verdana,sans-serif;">Anyway, what you see below is the short "paper" I sketched up back then on the subject:</span><br />
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<span style="color: blue;"><b>Flat Surface RR from
Roller Testing – Tom Anhalt – 5/2/06</b></span></div>
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</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;">The power required to turn a wheel on a
drum at a specific speed is governed by the equation:</span></div>
<span style="color: blue;">
</span>
<br />
<div align="CENTER" style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div align="CENTER" style="margin-bottom: 0in;">
<span style="color: blue;">P<sub>Drum </sub> =
Crr<sub>Drum</sub> x V<sub>Drum</sub> x M x g (a)</span></div>
<span style="color: blue;">
</span>
<br />
<div align="CENTER" style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;">Where,</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;">P<sub>Drum </sub> = Power required to
turn drum (Watts)</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;">Crr<sub>Drum</sub> = Coefficient of
Rolling Resistance of the tire on the drum (unitless)</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;">V<sub>Drum</sub> = The tangential
velocity of the drum (m/s)</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;">M = The mass load of the wheel on the
drum (kg)</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;">g = gravitational constant = 9.81 m/s<sup>2</sup></span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;">Rearranging equation (a) to solve for
the Crr of the tire on the drum results in:</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div align="CENTER" style="margin-bottom: 0in;">
<span style="color: blue;">Crr<sub>Drum</sub> = P<sub>Drum</sub>
/ (V<sub>Drum</sub> x M x g) (b)</span></div>
<span style="color: blue;">
</span>
<br />
<div align="CENTER" style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div align="CENTER" style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;">Then the contact patch deformation of a
tire of a specific diameter and a roller of a specific diameter can
be equated to the deformation of an equivalent diameter tire on a
flat surface using the following equation [Bicycling Science, 3<sup>rd</sup>
edition, pg 211]:</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div align="CENTER" style="margin-bottom: 0in;">
<span style="color: blue;">1/r<sub>eq</sub> = 1/r<sub>1</sub>
+ 1/r<sub>2</sub> (c)</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;">Where,
</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;">r<sub>eq</sub> = equivalent wheel
radius</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;">r<sub>1</sub> = tested wheel radius</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;">r<sub>2</sub> = tested drum radius</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;">For convenience purposes, this equation
can be rewritten using the appropriate diameters (r x 2) and is then:</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div align="CENTER" style="margin-bottom: 0in;">
<span style="color: blue;">1/D<sub>eq</sub> =
1/D<sub>wheel</sub> + 1/D<sub>Drum</sub> (d)</span></div>
<span style="color: blue;">
</span>
<br />
<div align="CENTER" style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;">For a tire of a given construction, it
has been shown that the Crr varies inversely proportionally to the
wheel radius, and thus the wheel diameter, in the range of D<sub>wheel</sub><sup>0.66
</sup>to D<sub>wheel</sub><sup>0.75</sup> [Bicycling Science, 3<sup>rd</sup>
edition, pg. 226]. To simplify for this purpose, the assumption is
made that the Crr varies inversely proportionally to D<sub>wheel</sub><sup>0.7</sup></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;">From this, it can be then written that:
</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div align="CENTER" style="margin-bottom: 0in;">
<span style="color: blue;">Crr<sub>flat</sub> /
Crr<sub>Drum</sub> = D<sub>eq</sub><sup>0.7</sup> / D<sub>wheel</sub><sup>0.7</sup>
(e)</span></div>
<span style="color: blue;">
</span>
<br />
<div align="CENTER" style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;">Equation (e) can be combined with (d)
and rearranged to give:</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div align="CENTER" style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div align="CENTER" style="margin-bottom: 0in;">
<span style="color: blue;">Crr<sub>flat</sub> =
Crr<sub>Drum</sub> x [ 1 / (1 + D<sub>wheel</sub>/D<sub>Drum</sub>)]<sup>0.7</sup>
(f)</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;">Substituting equation (b) for Crr<sub>Drum</sub>
in equation (f) results in:</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div align="CENTER" style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div align="CENTER" style="margin-bottom: 0in;">
<span style="color: blue;"><b>Crr</b><sub><b>flat</b></sub><b>
= [P</b><sub><b>Drum</b></sub><b> / (V</b><sub><b>Drum</b></sub><b> x
M x g)] x [ 1 / (1 + D</b><sub><b>wheel</b></sub><b>/D</b><sub><b>Drum</b></sub><b>)]</b><sup><b>0.7</b></sup><b>
(g)</b></span></div>
<span style="color: blue;">
</span>
<br />
<div align="CENTER" style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div align="CENTER" style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div align="CENTER" style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><b>Mass Correction Factor:</b></span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;">When doing Crr testing on rollers, the
mass loading of the wheel or wheels will need to be corrected due to
front-rear loading ratio and the fact that 2 offset rollers contact
the rear wheel, thereby increasing the normal force on the rollers
due to geometry effects.</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><u>Rear Wheel Only Case </u>- When the
test is done using a front fork mount and only the rear wheel
contacting the rear rollers of the test setup, the following
“effective mass” (M<sub>eff</sub>) needs to be calculated and
substituted for M in equation (g) :</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div align="CENTER" style="margin-bottom: 0in;">
<span style="color: blue;">M<sub>eff</sub> = M<sub>rear
</sub>/ cos [arcsin (X/(D<sub>wheel</sub> + D<sub>Drum</sub>))] (h)</span></div>
<span style="color: blue;">
</span>
<br />
<div align="CENTER" style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;">Where:</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;">X = separation distance of rear roller
axles (consistent units with D<sub>wheel</sub> and D<sub>Drum</sub>)
</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;">M<sub>rear</sub> = vertical mass load
on rear wheel (kg)</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><u>Front and Rear Rollers</u> - When
the test is performed using both the front and rear rollers, the
following Meff needs to be calculated and substituted for M in
equation (g) :</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div align="CENTER" style="margin-bottom: 0in;">
<span style="color: blue;">M<sub>eff</sub> = M<sub>front</sub>
+ M<sub>rear</sub> / cos [arcsin (X/(D<sub>wheel</sub> + D<sub>Drum</sub>))]
(i)</span></div>
<span style="color: blue;">
</span>
<br />
<div align="CENTER" style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;">Where:</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;">M<sub>front</sub> = vertical mass load
on the front wheel (kg)</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><b>Power Correction:</b></span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;">Depending on the method of power
measurement, the following offsets can be used to account for
drivetrain and drum rotation losses in the calculation of P<sub>Drum</sub>
for use in equation (g):</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><u>For Powertap</u> - P<sub>Drum</sub>
= P<sub>Powertap</sub> – 5W (accounts for drum bearing losses)
(j)</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><u>For SRM</u> - P<sub>Drum</sub> =
P<sub>SRM</sub> – 15W (accounts for drum bearings and driveline
losses) (k)</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;">Where:</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;">P<sub>Powertap</sub> and P<sub>SRM</sub>
are the power readouts (W) from the appropriate power meters.</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;">These power offsets are somewhat
arbitrary and should be modified if better data is known about the
particular test setup.</span></div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<br /></div>
<div style="margin-bottom: 0in;">
<span style="color: blue;"><span style="color: black;"><span style="font-family: Verdana, sans-serif;">That's basically it. I'd like to note a couple things about the last section on "Power Correction". First, after doing a bunch of testing since then, I don't bother accounting for the drum bearing losses. Also, when using a crank-based power meter, like an SRM or a Quarq Cinqo, I've found (after using a PT in conjunction for quite a few tests) that it makes more sense to account for the drivetrain friction with just a straight percentage. A typical value taken for drivetrain losses on bicycles is ~2.5%, but that is typical at higher power levels (i.e. higher chain tensions). For the lower power levels I usually see in tire testing with a rear only roller setup (usually ~100W or less, with the better tires closer to ~50W) I typically see ~5% drivetrain losses, so that's the figure I use.</span></span></span></div>
<div style="margin-bottom: 0in;">
<br /></div>
<div style="margin-bottom: 0in;">
<span style="color: blue;"><span style="color: black;"><span style="font-family: Verdana, sans-serif;">It's important to remember that the point of this is to get a "ballpark" feel for the difference between tires, not necessarily an absolutely accurate value. It's been shown that percent difference in power requirements on the rollers equate very well to percent differences on the road. What we're really looking for is a sort of "scaling factor" to put the differences seen on the rollers in perspective as to what to expect on the road. </span></span></span></div>
<div style="margin-bottom: 0in;">
<br /></div>
<div style="margin-bottom: 0in;">
<span style="color: blue;"><span style="color: black;"><span style="font-family: Verdana, sans-serif;">There you go...equation (g) is easily written into a spreadsheet. After that, it just takes a few measurements of the roller setup, weighing the rear wheel load, and some time on the rollers with a power meter equipped bike and nearly anyone can "test tires". </span></span></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<span style="color: blue;"><br /></span>
</div>
<span style="color: blue;">
</span>
<br />
<div style="margin-bottom: 0in;">
<br /></div>
<div style="margin-bottom: 0in;">
<br /></div>
<div style="margin-bottom: 0in;">
<br /></div>
<div style="margin-bottom: 0in;">
<br /></div>
<div style="margin-bottom: 0in;">
<br /></div>
<div style="margin-bottom: 0in;">
<br /></div>
<div align="CENTER" style="margin-bottom: 0in;">
<br /></div>
Tom Anhalthttp://www.blogger.com/profile/08175472546482777614noreply@blogger.com9tag:blogger.com,1999:blog-6080071290235905056.post-58898862932051744352013-02-01T18:42:00.000-08:002013-09-12T19:38:29.551-07:00LeMond Power Pilot - Does it give good numbers?<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgM3v2PwYRh1wrMseLdOvqAZuk3cIPfj24V9vb81mOu2Kc5N_-zAg6O4MXB6x3Zx46nQF-fZKUW3GMVLU11EHW07p2CWdAX8T-daLu5Pn61U-LZbQ7ci72-sDMQGcE2SmYwpU1scQdkElE/s1600/PP.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="265" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgM3v2PwYRh1wrMseLdOvqAZuk3cIPfj24V9vb81mOu2Kc5N_-zAg6O4MXB6x3Zx46nQF-fZKUW3GMVLU11EHW07p2CWdAX8T-daLu5Pn61U-LZbQ7ci72-sDMQGcE2SmYwpU1scQdkElE/s400/PP.jpg" width="400" /></a></div>
<div style="text-align: center;">
<span style="font-family: Verdana,sans-serif;"><br /></span>
</div>
<span style="font-family: Verdana,sans-serif;"><br /></span>
<br />
<div class="separator" style="clear: both; text-align: center;">
</div>
<div align="LEFT" style="font-weight: normal; margin-bottom: 0in;">
<span style="font-family: Verdana,sans-serif;"><span style="font-size: small;"><span style="font-size: small;">Considering that <span style="font-size: small;">it was <a href="http://www.lemondrevolution.com/pages/press" target="_blank">announced today</a> that Greg LeMond had formed a new venture to sell the Revolution <span style="font-size: small;">trainer, and that </span></span>my last post had dealt with the Revol<span style="font-size: small;">ution<span style="font-size: small;">, I thought it would be a good time to also talk about the P<span style="font-size: small;">ower Pilot device that Le<span style="font-size: small;">Mond sells for use with the trainer<span style="font-size: small;">. <span style="font-size: small;">I<span style="font-size: small;">f someone <span style="font-size: small;">already <span style="font-size: small;">has a <i>non</i>-wheel based power meter on their bike, then the Power Pilot would be a bit redunda<span style="font-size: small;">nt. But, fo<span style="font-size: small;">r those who use a PT wh<span style="font-size: small;">eel primarily, or don't have another form of power measurement, the Power Pilot could be a good alternative for dete<span style="font-size: small;">rmin<span style="font-size: small;">ing the "load" during a trainer workout. </span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span><span style="font-family: Verdana,sans-serif;">The
following is a brief look at the power reporting and recording performance of the LeMond Power Pilot. In particular, it is compared to the output of a “known
good” Quarq CinQo crank-based power meter. "Known good" in this sense is a <span style="font-size: small;">power meter which <span style="font-size: small;">has had it's torque slope checked and adjusted and <span style="font-size: small;">has a zero offset that is stable.</span></span></span>
</span></div>
<br />
<div align="LEFT" style="font-weight: normal; margin-bottom: 0in;">
<span style="font-family: Verdana,sans-serif;"><br /></span>
</div>
<span style="font-family: Verdana,sans-serif;">
</span>
<br />
<div align="LEFT" style="font-weight: normal; margin-bottom: 0in;">
<span style="font-family: Verdana,sans-serif;"><span style="font-size: small;">BACKGROUND</span></span></div>
<span style="font-family: Verdana,sans-serif;">
</span>
<br />
<div align="LEFT" style="font-weight: normal; margin-bottom: 0in;">
<span style="font-family: Verdana,sans-serif;"><span style="font-size: small;"> The
LeMond Power Pilot is a device designed to be used in conjunction
with the LeMond Revolution trainer to primarily monitor and record
the training efforts of the rider. The Revolution trainer is a high
inertia wind trainer with the somewhat unique configuration whereby
the rear wheel of the attached bike is removed and is not a part of
the driven assembly. The chain of the bike drives a rear cassette
which is attached to a relatively high mass flywheel through a belt
drive gear reduction system. In my last blog post ("<a href="http://bikeblather.blogspot.com/2013/01/whats-virtual-cda-and-crr-of-lemond.html" target="_blank">What's the </a><span style="font-size: small;"><a href="http://bikeblather.blogspot.com/2013/01/whats-virtual-cda-and-crr-of-lemond.html" target="_blank">Virtual C</a><span style="font-size: small;"><a href="http://bikeblather.blogspot.com/2013/01/whats-virtual-cda-and-crr-of-lemond.html" target="_blank">dA and C</a><span style="font-size: small;"><a href="http://bikeblather.blogspot.com/2013/01/whats-virtual-cda-and-crr-of-lemond.html" target="_blank">rr of the Le</a><span style="font-size: small;"><a href="http://bikeblather.blogspot.com/2013/01/whats-virtual-cda-and-crr-of-lemond.html" target="_blank">Mond Revolution Trainer</a>"<span style="font-size: small;">)</span></span></span></span></span></span></span><span style="font-family: Verdana,sans-serif;">, it was <span style="font-size: small;">sh<span style="font-size: small;">own</span></span> that this system
“mimics” the aero drag of a typical sized rider on a road bike
(CdA = ~0.35 m^2) and the rolling resistance of average tires (Crr =
~ .005). The inertial mass was also found to be equivalent to a
rider mass of ~45kg, which although it is less than the mass of a
typical rider, it is far higher than the much lower inertial masses
of most indoor trainers on the market today. This accounts for the
often reported excellent “road feel” of the Revolution trainer.</span></div>
<div align="LEFT" style="font-weight: normal; margin-bottom: 0in;">
<br /></div>
<span style="font-family: Verdana,sans-serif;">
</span>
<br />
<div align="LEFT" style="font-weight: normal; margin-bottom: 0in;">
<span style="font-family: Verdana,sans-serif;"><span style="font-size: small;"> The
Power Pilot uses an ANT+ sensor to read the drive pulley rotational
velocity, and by extension, the flywheel speed during operation.
Along with the known aero properties of the flywheel fan, the aero
drag power is calculated using that speed measurement and an estimate
of the air density (based upon the user entered altitude, an
internal temperature sensor, and an internal humidity sensor.) The
speed sensor is also used to determine the acceleration/deceleration
of the flywheel mass to account for that in the power reporting.
Additionally, the Power Pilot firmware allows for a coastdown
calibration to be performed which then accounts for any unit to unit
variation in the “fixed” losses of the mechanism.</span></span></div>
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</span>
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<span style="font-family: Verdana,sans-serif;"><br /></span>
</div>
<span style="font-family: Verdana,sans-serif;">
</span>
<br />
<div align="LEFT" style="font-weight: normal; margin-bottom: 0in;">
<span style="font-family: Verdana,sans-serif;"><span style="font-size: small;">THE
TEST AND RESULTS</span></span></div>
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</span>
<br />
<div align="LEFT" style="font-weight: normal; margin-bottom: 0in;">
<span style="font-family: Verdana,sans-serif;"><span style="font-size: small;"> In
order to determine how well the Power Pilot performs these
calculations, it was decided to compare the Power Pilot output to the
power values measured using a Quarq CinQo crank-based power meter.
The particular CinQo used in this testing is a “known good” unit
which has been recently calibrated for torque slope and demonstrates
a very stable zero offset. To make the comparison, a ride was
undertaken whereby a “cassette sweep” was performed. The ride
started with the bike in a gear selection of 53/25 and then
progressed down the cassette every ~1.5 minutes until a gear
selection of 53/12 was used, all the while keeping a constant 60 rpm
cadence. Then, the chainring was shifted to a 39T and the
progression was repeated partially up the cassette. Finally, two
additional runs were taken at a higher cadence (and thus power). A
plot of both power traces vs. time is shown below:</span></span></div>
<div align="LEFT" style="font-weight: normal; margin-bottom: 0in;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjqkSCRAbe0NdBcRpUh91_oZXLCHvgIirfR-_Y78B7It1jKbTDeJcsh0ig38BPLLPclu6QL46gfY4DCQAMqRhwJqAXyCwkdaDlap6gunGXBY_YyDo6qKlZ37m35cFOOdG0_A8AcODgCz-Q/s1600/PPvsCinQo_trace.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="329" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjqkSCRAbe0NdBcRpUh91_oZXLCHvgIirfR-_Y78B7It1jKbTDeJcsh0ig38BPLLPclu6QL46gfY4DCQAMqRhwJqAXyCwkdaDlap6gunGXBY_YyDo6qKlZ37m35cFOOdG0_A8AcODgCz-Q/s640/PPvsCinQo_trace.jpg" width="640" /></a></div>
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<br /></div>
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</span>
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<div align="LEFT" style="font-weight: normal; margin-bottom: 0in;">
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</div>
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</span>
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<div align="LEFT" style="font-weight: normal; margin-bottom: 0in;">
<span style="font-family: Verdana,sans-serif;"><span style="font-size: small;"> Looking
closely, one can see that aside from a slight offset, the values
reported by each power meter “track” very closely to each other.
This can further be seen if the power values relative to each other
are plotted on a point-by-point basis. The plot below shows the
power reported at each point in time with the CinQo power values on
the x-axis and the Power Pilot values on the y-axis.</span></span></div>
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</span>
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</div>
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</div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhAWSqKdKQs_6WHm1GzGA41pT9rBFh9G1tfKsBwO6rOGN9OODkBDYil6EwxPYMVp8s4x1Wdu2YH__h5RvRv6ccIOlb2grdFtDx7ekdXKn-S7xSK11df-Hr7bNEFkIl8y9I63SLBzhGGfFg/s1600/PPvsCinQo_ptbypt.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="440" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhAWSqKdKQs_6WHm1GzGA41pT9rBFh9G1tfKsBwO6rOGN9OODkBDYil6EwxPYMVp8s4x1Wdu2YH__h5RvRv6ccIOlb2grdFtDx7ekdXKn-S7xSK11df-Hr7bNEFkIl8y9I63SLBzhGGfFg/s640/PPvsCinQo_ptbypt.jpg" width="640" /></a></div>
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<span style="font-family: Verdana,sans-serif;"><br /></span>
</div>
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</span>
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<div align="LEFT" style="font-weight: normal; margin-bottom: 0in;">
<span style="font-family: Verdana,sans-serif;"><br /></span>
</div>
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</span>
<br />
<div align="LEFT" style="font-weight: normal; margin-bottom: 0in;">
<span style="font-family: Verdana,sans-serif;"><span style="font-size: small;"> Typically,
due to factors such as variations in recording rates, calculation
algorithms, etc. the sort of plot above doesn't turn out very well as
a comparison tool for power meters. However, in this case, the
point-by-point power reporting is fairly good and it appears that the
Power Pilot reports ~94% of the power reported by the CinQo.
Considering that the Power Pilot estimate is taking place
“downstream” of the bicycle drivetrain losses (much like a
PowerTap wheel) in comparison to the crank-based location of the
CinQo, a ~6% drivetrain power loss is reasonable, and typical of an
average drivetrain.</span></span></div>
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<br /></div>
<span style="font-family: Verdana,sans-serif;">
</span>
<br />
<div align="LEFT" style="font-weight: normal; margin-bottom: 0in;">
<span style="font-family: Verdana,sans-serif;"><span style="font-size: small;">Rather
than looking at the point-by-point plot and it's curve fit, often
it's more useful to look at a plot of the averages reported by the
power meters over constant power sections. The plot below is the
same as the previous plot, but the averages over each of the
“intervals” of the cassette sweep are plotted and a curve is fit
to them. As can be seen the fit is fairly “tight” to the data
and the slope of the fit (i.e. the drivetrain loss) is similar to
that reported above, albeit slightly lower. This appears to point
out that the correlation between the 2 devices may be slightly better
during constant power efforts. Alternatively, it could reveal that
the time correlation of the point-by-point data looked at above may
be slightly “off”.</span></span></div>
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<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEin1BJ2BPFDkVBCbuJJ0Ml5x9_d94oHcTdMeP2R_uPW3KBs8xWRb6AEW6FaOnL87PB2KH-oheXudy4efqbumxiWBJhrRl3ccPd5C6ThM1NZQe2Eq4qywcfqdC4Bw_RPVy2gCvHJerCD_Hs/s1600/PPvsCinQo_fit.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="372" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEin1BJ2BPFDkVBCbuJJ0Ml5x9_d94oHcTdMeP2R_uPW3KBs8xWRb6AEW6FaOnL87PB2KH-oheXudy4efqbumxiWBJhrRl3ccPd5C6ThM1NZQe2Eq4qywcfqdC4Bw_RPVy2gCvHJerCD_Hs/s640/PPvsCinQo_fit.jpg" width="640" /></a></div>
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<div align="LEFT" style="font-weight: normal; margin-bottom: 0in;">
<span style="font-family: Verdana,sans-serif;"><br /></span>
</div>
<span style="font-family: Verdana,sans-serif;">
</span>
<br />
<div align="LEFT" style="font-weight: normal; margin-bottom: 0in;">
<span style="font-family: Verdana,sans-serif;"><span style="font-size: small;"> However, understanding where
the power meters <i>don't </i><span style="font-style: normal;">agree
can sometimes be much more enlightening in that it can reveal
systemic difference between the devices. One tool for doing this is
something called a “Mean – Difference” Plot. This plot shows
the difference between the power values reported by the 2 devices
plotted against their average. The Mean-Difference plot of this ride
is shown below:</span></span></span></div>
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<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhsFa09yJZ5juwDwHhu5ZTSJ9JWn_QwY8j3NL7jy2B11hHZD9S9GfBNBzIA85_3_axjcLYDPGSQRfjvBybNAFpXhhaiv1myHTWF4vPH6lVL0ouB8L__WqiRfqAa7yCwwJnZEcA1Q0_Rx6I/s1600/PPvsCinQo_tukey.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="368" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhsFa09yJZ5juwDwHhu5ZTSJ9JWn_QwY8j3NL7jy2B11hHZD9S9GfBNBzIA85_3_axjcLYDPGSQRfjvBybNAFpXhhaiv1myHTWF4vPH6lVL0ouB8L__WqiRfqAa7yCwwJnZEcA1Q0_Rx6I/s640/PPvsCinQo_tukey.jpg" width="640" /></a></div>
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</div>
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</span>
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<div align="LEFT" style="font-style: normal; font-weight: normal; margin-bottom: 0in;">
<span style="font-family: Verdana,sans-serif;"><br /></span>
</div>
<span style="font-family: Verdana,sans-serif;">
</span>
<br />
<div align="LEFT" style="font-style: normal; font-weight: normal; margin-bottom: 0in;">
<span style="font-family: Verdana,sans-serif;"><span style="font-size: small;"> The things to look for in this type of plot that reveal
systemic “issues” are characteristics like the spread of the
points getting larger or smaller with the mean power values or the
difference not trending in a monotonic fashion. Neither of these
types of issues appear to be present above, implying that the Power
Pilot “agrees” with the CinQo output in a consistent and
predictable manner.</span></span></div>
<div align="LEFT" style="font-style: normal; font-weight: normal; margin-bottom: 0in;">
<br /></div>
<span style="font-family: Verdana,sans-serif;">
</span>
<br />
<div align="LEFT" style="font-style: normal; font-weight: normal; margin-bottom: 0in;">
<span style="font-family: Verdana,sans-serif;"><span style="font-size: small;"> Another area of interest for comparisons of this type
is how the 2 devices respond to sprint type efforts. An additional
ride was undertaken where a pair of short sprints were performed in
order to see if there were any anomalies between how each device
reported these efforts. As can be seen below, the shapes of the
curves are very similar with the peak values also being very close to
each other.</span></span></div>
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</span>
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<span style="font-family: Verdana,sans-serif;"><br /></span>
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjbo7lmOD6V-C5HF-aCXchJTAVk4nph_xIZe-iQM42JZGwy_6t74DliSy8U85RKIPXdv3gQIk-oKA6IndXEtNvTamqqZsW173ytYfE6YwzcGAbqvzblEONNx2HUZWadT2j1fDfFhhqGKpQ/s1600/Sprints.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="332" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjbo7lmOD6V-C5HF-aCXchJTAVk4nph_xIZe-iQM42JZGwy_6t74DliSy8U85RKIPXdv3gQIk-oKA6IndXEtNvTamqqZsW173ytYfE6YwzcGAbqvzblEONNx2HUZWadT2j1fDfFhhqGKpQ/s640/Sprints.jpg" width="640" /></a></div>
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<div align="LEFT" style="font-style: normal; font-weight: normal; margin-bottom: 0in;">
<span style="font-family: Verdana,sans-serif;"><br /></span>
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<div align="LEFT" style="font-style: normal; font-weight: normal; margin-bottom: 0in;">
<span style="font-family: Verdana,sans-serif;"><span style="font-size: small;">CONCLUSIONS</span></span></div>
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</span>
<br />
<div align="LEFT" style="font-style: normal; font-weight: normal; margin-bottom: 0in;">
<span style="font-family: Verdana,sans-serif;"><span style="font-size: small;"> This brief examination of the power output of a LeMond
Power Pilot on a Revolution trainer shows that it does an acceptable
job at determining and recording the rider's power output when
compared to a “known good” crank-based power meter. The power
output is similar to what one would expect to see from a hub-based
power meter, which is favorable for the likely customer base for this
product, namely users with no other power meter or Power Tap owners
who want to train indoors with and/or by power.</span></span></div>
Tom Anhalthttp://www.blogger.com/profile/08175472546482777614noreply@blogger.com0