Sunday, March 19, 2017

Holy Moly...Vittoria Corsa Speed TLR




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!"

To cut to the chase...I tested the Corsa Speed in 3 ways:

  1. First, on my standard test wheel (Mavic Open Pro) with a latex tube inside, 120psi.
  2. Next, on a Jet6+ wheel with a latex tube, 100psi
  3. Lastly, on the Jet6+ wheel set up tubeless, with 40ml of Orange Seal.
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:

Vittoria Corsa Speed TLR 23C, latex tube, Open Pro (120 psi)  = .0025, 23W for pair @ 40 kph
Vittoria Corsa Speed TLR 23C, latex tube, Hed Jet6+ (100 psi) = .0025, 24W for pair @ 40 kph
Vittoria Corsa Speed TLR 23C, tubeless, Hed Jet6+ (100 psi)    = .0025, 24W for pair @ 40 kph



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.

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.


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.

Coating inside casing. Appears to be same as sidewall coating


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.


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.


There you go...a new "top dog" has been confirmed.

Monday, March 6, 2017

Stinner Aero Camino - Hot Rod American Steel - Part I

Ever since my "Win Tunnel Playtime" 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.


Stinner Aero Camino: Road Art

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?

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?

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...

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.

1986 Bianchi Sport SX "Violet" - After surviving the 2016 Belgian Waffle Ride

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 NAHBS "Rookie of the Year" award in 2012: Aaron Stinner, of Stinner Frameworks.

Thus began the project that became: The Stinner Aero Camino custom prototype.

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.

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.

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.

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.

True Temper Velo Seatstays on a Yamaguchi road bike


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.

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!

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 old aero bicycle tube 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...

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 :-) 

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... 

Columbus Life Aero tube tracing


...and then modeled the tube in Solidworks...

Solidworks Sketch Details


...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:

Solidworks Flow Simulation 2D Result Plot


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).

Estimated Power for Downtube @ 40kph


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!

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!

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:



Here's how the frameset shook out material-wise:

-Fork is first generation Cervelo S5 model 

Tube specs is as follows: 

-Head Tube: 44mm with Chris King Inset HS 

-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. 

-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) 

-Seat Tube: True Temper HVERST1 

-Chain Stays: Columbus life Oval 

-Seat Stays: True Temper Velo Seat Stays (teardrop shape designed by Yamaguchi) 

-Bottom Bracket: BSA threaded 


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"!

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.

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.

Next up: The build, the paint, and the assembly.

Aaron Stinner and his crew from Stinner Frameworks are going to be displaying all of their awesome wares this coming weekend at the North American Handbuilt Bicycle Show (NAHBS) 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.




Sunday, January 22, 2017

Getting Caught Up II

Yeah...it's been awhile. Lots of things happening in the last year.

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 (see report here), 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:

Continental GP4000SII   25C = .0031, 28W for pair @ 40kph
Continental GP Attack   22C  = .0033, 31W for pair @ 40kph
Continental GP4000SII   23C = .0034, 31W for pair @ 40kph
Schwalbe One Tubeless 25C = .0037, 34W for pair @ 40kph
Schwalbe One Tubeless 23C = .0041, 38W for pair @ 40kph
Felt TTR1                      23C = .0048, 45W for pair @ 40kph
Continental Gatorskin     25C = .0048, 45W for pair @ 40kph
Continental Gatorskin     23C = .0052, 48W for pair @ 40kph

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.

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:

Continental GP Force   24C = .0030, 27W for pair @ 40kph
Continental GP TT       23C = .0028, 26W for pair @ 40kph

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").

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:

Continental SuperSonic 20C = .0030, 28W for pair @ 40kph

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.

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).

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:

Specialized S-Works Turbo Tubeless 26C = .0032, 30W for pair @ 40kph

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!

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.

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:

Sunday, March 6, 2016

Win Tunnel Playtime - Part 3 (The "After Party")


About a week after the fun session in the Specialized Win Tunnel (outlined in Part 1 and Part 2), 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:

Roval CLX64 Wheel


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.

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. 

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.

The Crr results for the 6 Specialized tires are as follows:

Specialized S-Works Turbo 22C = .0041, 38W for pair @ 40kph
Specialized S-Works Turbo 24C = .0036, 33W for pair @ 40kph
Specialized S-Works Turbo 26C = .0035, 32W for pair @ 40kph
Specialized S-Works Turbo 28C = .0035, 32W for pair @ 40kph (note: AC101 disc wheel)

Specialized Turbo Cotton 24C = .0029, 27W for pair @ 40kph
Specialized Turbo Cotton 26C = .0028, 26W for pair @ 40kph

By comparison, here's the results for the "benchmark" GP4000S (tested on Open Pro @120psi):

Continental GP4000S 23C = .0034,  31W for pair @ 40kph

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").

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? 

Well, to truly get at that answer requires some fairly detailed modeling, such as that performed by BestBikeSplit.com, 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.

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.

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.


Roval CLX64, 38kg load, 35 kph ground speed


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' " (Here, and here)...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.

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.

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.

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:



Combining that plot with the Crr results like we did above, results in the following overall expected power plot:



I think I'll just leave that there without further comment...Enjoy!

The spreadsheets containing the data and calculations can be viewed here:

- Roval CLX64 plus Specialized Tires

- All wheels from Win Tunnel Visit

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:

Sunday, October 25, 2015

Win Tunnel Playtime - Part 2


In the previous blog post (Win Tunnel Playtime - Part 1), 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 Stinner Frameworks custom steel road frame), and for comparison sake, we also tested a brand new Specialized Venge ViAS which just happened to be available <smirk>.

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:

  1. 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".
  2. Same as #1, with front wheel swapped for a Roval CLX64 with a 22C Specialized S-Works Turbo tire.
     
  3. Same as #1, but with front wheel swapped for Flo 90 with 23C Continental Super Sonic tire.
  4. Same as #3, but with round bottle and bottle cage swapped over from Venge ViAS frame on downtube (low location).
  5. Venge ViAS with Roval CLX64 wheels, 22C Specialized S-Works Turbo front, 24C rear. Round bottle on downtube.


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.





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.

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.



Next was the Stinner with the Hed Jet6+ and Turbo Cotton tires (in my "crit setup")


And finally, we swapped the front wheel for the Roval CLX64 and 22C S-Works Turbo.



Here's how that all played out:


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.  

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.

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.

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.

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: Bike and Rider data

Monday, October 5, 2015

Win Tunnel Playtime - Part 1



As I mentioned in my last post, thanks to the generosity of Specialized, 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.

Earlier this year, Chris had sent me an email asking if I was interested in participating in one of their videos 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?

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.



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.

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.



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?).

Looking closer at just the Jet 6+ runs, here's how they looked:



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.

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:











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.




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!




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.

For those interested, the entire data set can be found in this spreadsheet here: Wheel Aero Data

Monday, September 7, 2015

Getting 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.

The spreadsheet linked to in the upper right corner of this blog page has had the following entries added:

Continental Supersonic 23C (New) = .0029, 27W for pair @ 40kph
Continental Attack 22C (~140 miles, "magic tire") = .0029, 27W for pair @ 40kph
Continental Force (used) = .0034, 32W for pair @ 40kph
Continental Attack 22C (ave. of 2 new) = .0036, 33W for pair @ 40kph
Continental Attack 22C (1 of 2 above, 118mi) = .0036, 33W for pair @ 40kph
Clement Strada LGG Gumwall 25C = .0045, 42W for pair @ 40kph
Kenda Kountach 25C = .0049, 45W for pair @ 40kph

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...

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.

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.

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!