From what I've seen the separation between the least aero and most aero tires of similar width is about 50g, or about 5W at the 40kph standard for Crr testing.

And usually it's must less than 50g near zero yaw. Most of the Conti 4000SII magic occurs at higher yaw.

If two Corsa Speed save ~4W vs. the Turbo Cotton at that speed it'd have to be *really* bad at aero to make it not worthwhile. And the Crr benefits occur at both wheels vs. aero which is likely more important up front.

Curious, but have people done the math on the effect of weight of rider on relative importance of rolling resistance to aero? (Significant enough that a 100lb rider should consider different tires than a 200lb one? 150?)

Assuming the Crr results hold up, I will certainly switch out the cotton turbo I am using on my disc. The front is trickier because I am using a TriSpoke/20mm Conti SS. I doubt they will make 20-21mm version, so I need to consider if the Crr saving offset the difference in aero drag and watts to spin. I am also riding an old nose cone Shiv and a wide rim really makes the arms on the TRP brakes stick out in the wind. That frame was designed before wide rims became popular so wheels like my HED Stinger don't even fit without shaving down the brake pads or modifying the stops on the brakes.

If I ever get to do an ERO session I will definitely spend some time on front wheel choice.

anyone knows when the graphene corsas will be available?

February.

My LBS in Houston has them in stock

How much are they at your local shop?

around $90 I think

Assuming the Crr results hold up, I will certainly switch out the cotton turbo I am using on my disc. The front is trickier because I am using a TriSpoke/20mm Conti SS. I doubt they will make 20-21mm version, so I need to consider if the Crr saving offset the difference in aero drag and watts to spin.

Every "open tubular" aero test I've seen shows pretty abysmal aero performance. The only viable place to use them is on the rear. Stick with your Supersonic.

I don't know. I've probably seen less than you, but this plot from Flo is one data point that the "abysmal" doesn't really start until around 7.5 degrees yaw. (Vittoria Open Triathlon EVO)

The 20mm SS is, I believe, roughly equivalent to the 23mm GP4KSII in Crr? So if we believe the (still to be verified) 6.5W @ 40kph Crr difference between the GP4KSII and Corsa Speed, then the Corsa Speed is a clear winner over the 20mm SS out to 7.5 degrees.

Average-yaw-experienced is rider and course dependent, and still an open topic even then, but, personally, I'd prefer to optimize from 0 to 7.5 deg. Unless I knew my course had a big-ass pure sidewind leg or something.

The 20mm SS is, I believe, roughly equivalent to the 23mm GP4KSII in Crr?

The 20mm SS is consistently better in my testing. Worst SS (5 samples) is better than best GP4000 23mm (3 samples), with ~10% on average.

Note the Vittoria 22mm is very narrow. It might actually be the old 20mm casing size. Tom A and Specialized have some good data posted on this forum somewhere. Don't think they tested a 20mm SS, but the 23mm SS was very good in aero, and the 24mm Turbo Cotton was very poor.

Yaw sweep tests show that the higher yaw angles are rare in practice.

So ignore it? Bad idea for longer course tris. Pretty clearly a consideration for the recent IM Kona and IMAZ races. It will be this weekend at IM Coz too. There are other examples for HIM such as Honu, StG and Silverman. These are all popular races with plenty of ST participants. Bottom line is use suitable equipment for typical race conditions. It's pretty easy to punch your race into BBS and see predicted yaw.

I may be a bad example, but BBS tells me that 100% of my race at IMAZ was under 10% yaw.

Lol. Yes! You are the side of the equation where high speed, on and of course early, etc reduce yaw. Last year's conditions may have yielded different results, though the wind does seem to align somewhat along Beeline.

Unless BBS changed their models, they're still using weather station yaw distributions, which are generally not taken at ground elevation and overestimate yaw angles.

In this case it reads like the graphene their using is pretty much, in effect, fancy carbon black.

Proof in the eating of the pudding. Goodness knows I've got enough tires around right now as it stands, though.

---

The question of who is right and who is wrong has seemed to me always too small to be worth a moment's thought, while the question of what is right and what is wrong has seemed all-important.

-Albert J. Nock

Yaw sweep tests show that the higher yaw angles are rare in practice.

I didn't say anything about yaw.

It isn't looking good for Vittoria Corsa Speed.

Still wishing they'd test the Supersonic and Veloflex Record...

http://bikeboard.at/...-Welt-Pt.-2-th217501

That looks like it's just the Corsa, not the Corsa Speed. From the text and from looking at the sidewall of the tire in the picture. But maybe you meant it's not looking good for the Speed if the graphene Corsa didn't do as well as the regular Open Corsa EVO.

Though I'm feeling my stash of 23mm SuperSonic is staying safe from irrelevance.

My bad. You are correct, that apparently isn't the Corsa Speed. It appears that the Corsa has a thicker tread with a different construction than the Corsa Speed. It has kevlar in the casing also, and looks like more a replacement for the Pave. The anti-puncture layer looks different as well.

Thanks rruff for the link.

Testing with two different manufacturers is an excellent idea in this test ! Results are quite similar but it really gives a lot of credibility to this test ! Kudos to the magazine for taking the time to do it this way !

That graph raises some interesting points.
1. Wow those Mavics suck!
2. At 12-13 watts for the Specialized 24, there just isn't that much room for improvement. The graphene is going to have to be some pretty special secret sauce to get down to 10 or 11 watts.

I wonder what the physical limits of a bike tire are?

Wait... there's two versions of the Attack? Minor existential crisis here...

Clincher vs tubular.