Well, 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!
Anyway, here's the predicted on-road Crr for the 3 tires I tested today:
Continental GP4000S 23C = .0034
Specialized All Condition Pro II 23C = .0062
Specialized All Condition Armadillo Reflect 25C = .0077
The overall Crr chart now looks like this:
And here is the predicted power for 2 tires at 40kph (85kg total load):
As always, the entire spreadsheet is saved here:
Crr Spreadsheet
With the data we found yesterday I'm seeing a bit of a stand out! This is great data. Thanks for sharing it!
ReplyDeleteChris
A "bit"? Ya think?? ;-)
DeleteVittoria Crono Evo CS or Corsa Evo slick tubulars?
DeleteWhat's the question, Les?
DeleteQuestion was which to run but I jumped on the clincher bandwagon due to your work and voila 75 seconds faster this year than last year with a Raltech carbon disk cover on the back (same bike). Thanks very much, I sold my tubulars.
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ReplyDeleteTom, is the Vittoria Diamante Radial the replacement or similar to the Vittoria Diamante Pro II(The tire I am using now-can't seem to find about this tire)? Really the bottom line is, I am considering purchasing the 4000s and wondering if there would be that much of a difference?
ReplyDeleteNo, AFAIK it's a different model.
DeleteI have a tire that I have been very happy with, even with just a couple hundred miles on it. Going by feel, 'marketing', and comments by other folks, I'd like to think it does quite well with Crr numbers. Could I get it to you as a short term 'loaner' to run through your testing setup and have it compared with the other tires?
ReplyDeleteIts a Grand Bois Extra Leger 700x26c, sold by Compass Bicycles. Made by Panaracer with the same carcass as their tubulars.
great info but im a bit confused re 4000s rolling resistance. I see a 4000s at 29 up by the evo's and then a 4000s at 39 w butyl. Which 4000s configuration gives you the 29 rr??? I have a new pair of 4000s chili ready to use but if they roll at 39 they will end up training tires!! thanks
ReplyDeleteIt's the exact same tire in both cases. The difference is completely attributed to using latex tubes vs. butyl.
DeleteYes...running latex tubes saves that much effort.
WOW WOW WOW!!! That is amazing!!! so then there is no need to buy Evos....just run my new 4000's and latex!! Thank you so much Tom.
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ReplyDeleteTom, I was looking for a comparison of 23c vs 25c tires, particularly for the Continental GP4000S tire. I'm hearing that a 25c tire has less rolling resistance, but then it has to be heavier (more spinning mass), so presumably it would require more power, particularly when accelerating. Do you have numbers to compare? Otherwise, your thoughts? Thanks.
ReplyDeleteHi David,
DeleteTire mass is REALLY far down on properties that affect bike performance. The fact is that humans on bicycles accelerate EXTREMELY slowly, and thus the differences in mass you're talking about account for miniscule differences in power. To calibrate you on how miniscule, read this simplified analysis I did for Slowtwitch: http://www.slowtwitch.com/Tech/Why_Wheel_Aerodynamics_Can_Outweigh_Wheel_Weight_and_Inertia_2106.html
Now then, although 25C tires of a given construction can have lower Crr than the same construction 23C at a given pressure...in practice, most folks also lower the pressure and thereby "give back" most of that Crr advantage. On top of that, the wider tires will be slower aerodynamically. Personally, I don't see any reason for going that wide unless "comfort" is an issue (or the rider is heavy), and even then only on the rear.
Thanks for a great article and well researched and fact based, which is refreshing.
ReplyDeleteI have been developing my own tubeless sealant since 2007 which I have been using on Tubular, road tubeless and tubeless ready mountain bike tyres, and have managed to seal up to 6mm on mountain bike and 4mm cuts on road tubeless and tubular by playing with dilution of latex and the aggregates added to help coagulation.
in terms of "on the road" practicality, I have a couple of things to add:
1) road tubeless or tubular are by far the easiest to fix as the tube is either fixed to the carcass or non existent. putting sealant in an inner tube is not very successful at all. In a triathlon I carry a 60ml tube of very thick sealant and a co2, and by putting the cut dowwards you can usually seal a tire in about 1 min by putting the cut at the bottom and giving it a bust of co2, unless you have already lost too much pressure/sealant or the sealant is old and then you need to give it a dose of sealant via the valve and a burst of co2. As you say, if you have a big cut there is nothing you can do, but I do find that slipping a tube into a tubeless set-up less time consuming than pulling a tube out, folding it away (yes you should not just leave it there) and putting a new tube in. I have also had situations where I have put a new tube in and it blow out of the same hole and had to put a €20 bill in to stop the tube haemorrhaging through 2mm hole in the tyre sidewall from a stone strike, granted it was 31'C in Spain at 1,000m above sea level and I was using conti superlight which are very thin tubes, but that is the only way IMO to get the low rolling resistance with clinchers plus tubes, and my sealant would have probably sealed this, if not a patch is easy to put on inside and a new dose of sealant.
2) you mentions that tubeless is not good if you get pinch flats "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." pinch flats are an issue related to the tube being "pinched" between the wheel rim and the sidewall... if there is no tube, as is the case with tubeless, there is no pinchflat!
I am happy to send you some of my sealant if you wish to try BTW, but I have found it to seal much bigger than 1mm on road tubeless, as long as you put the cut down and allow a pool of sealant to work its magic.
you see people at the road side dabbing water on a hole that it pointing up to the sky wondering why the tyre will not seal with some residual latex that happens to be at the top... They would be better doing a rain dance and hoping the pool of sealant at the bottom will wick its way to the top :)