They aren't very knowledgeable.

I might classify ex-pro cyclists as being generally less knowledgeable than triathletes when it comes to gear selection ...

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Ed O'Malley
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It would depend on how you had to come down those big climbs. If it were a super twisty mountain road, with bad road surface, I would opt for a non disc wheel. I just remember even on flat courses with tight turns, having that disc slip out when cornering. A few turns is no big deal, but if you had 100's, then all that braking might add up to negating the advantage. All depends on your skills too...

Why would a disc be more likely to slip out on a sharp turn?

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Ed O'Malley
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Have you never ridden a disc before? Just spin one in your hands sometime and then turn it, see how much more it fights you than a regular wheel. Also discs are typically stiffer wheels, so when you get to max lean on a turn, it does not give like a less stiff wheel would, thus breaking loose a tiny bit earlier..

I thought Lanzarote had a no-disc wheel rule? Am I correct in remembering that?

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Now I get you're probably talking about established pros here but I can speak for myself and say that as of now I won't be running a disc at Eagleman 70.3 which is dead flat and maybe just a little windy. Not because I don't want to run one but simply because I don't have/can't afford one at the moment. I ran an aerojacket on my Chinese 88mm on my previous bike but now that I have disc brakes and no wheel sponsor I'm kind of SOL on the wheel front. I imagine that might be the case for some others as well.

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Nope, have seen several people ride in Lanzarote IM with a disc.

Sponsorship?

I'm gonna go with sponsorships / funding, handling, and a disc isn't that much faster than a decent deep rim on the back.

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Let's take one example from those Pros I'm talking about.

C. Wurf in IM France, and if I'm not mistaken also in Cannes triathlon few weeks ago.
He do have a disc and equipment available, as he have used it for other races.
And my understanding is that at least in cycling, he's very knowledgeable and have done testing with experts and top pro cycling team.

I ride a disc for virtually every race. I ride a HED so it's stiffness is similar to conventional wheels, but I am not convinced that a tiny difference in rim deflection will cause a noticeable difference in friction during a turn. Force vectors will be substantially the same.

Also for very sharp turns you won't be going super fast, the difference in gyroscopic effects between wheels should be limited, especially when there's only about a 15% difference in total weight of the wheel, and much of that extra weight for the disc is centered at a radius signifcantly within the outer radius of the wheel.

This sounds a lot like the cyclist mumbo-jumbo about how they can really feel the difference in the siffness of different top frames when they ride them.

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Ed O'Malley
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Why do you think that he is very knowledgeable?

Also for very sharp turns you won't be going super fast, the difference in gyroscopic effects between wheels should be limited, //

Why do you only talk about a couple turns, maybe in a race. How about the 100 that are long, sweeping, high speed ones, you know the ones that you get coming down a mountain?? You gonna choose a wheel for the 2 turns, or the 100??


And you are right, most people will not turn well enough to test the difference in holding power, but most pros do, so there you have it..

I assumed that as he comes from a pro cycling background and have been involved with Team Sky (now Ineos), which is known to have a lot of attention to details and "marginal gains". But I have never seen Chris Froome ride a hilly TT without a disc, so that assumption I made could be wrong :)

Pro cyclists are told what to ride.

Pro cyclists don't have to run off the bike - triathletes do. Maybe that has something to do with an ex pro cyclists choice? A solid disc can be harsh - a spoke wheel more forgiving for the run?

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He who understands the WHY, will understand the HOW.

Still not buying it. So if we go a little deeper into physics, the required coefficient of friction to prevent loss of traction increases as lean angle increases (if you do a little bit of math, it reduces down to tan(lean angle) = coefficient of friction)) A less-stiff wheel will increase the effective lean angle at the interaction point of the tire and the road, requiring more friction between the rubber and the asphalt, meaning that a less stiff wheel is actually MORE likely to slide out in a turn than a stiffer wheel is.

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Ed O'Malley
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I would love to see a world class criterium race with disc wheels. Maybe do 1/2 and 1/2 and see who actually comes out of the corners better! I know who I'm putting my money on..Good talk, but since I have my own data points on this, like with a lot of aero claims, I will go with what I know to be true, and not what the math says in some incomplete equation..

more flexible wheel has better bump compliance.

I remember years and years ago, when I kinda followed GP bike racing, that one of the manufacturers increased the lateral stiffness of their race bikes too much, making it harder to keep the bike planted in the corners. The next year they engineered flex back into the frame and swingarm.

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Ok.... feel & intuition vs. physics is often a battle here on slowtwitch (micro accelerations anyone???) and even more so with cyclists.

A crit throws in acceleration variables that are not present in triathlon. You are not accelerating at 1000 watts out of the turn so as not to lose the draft of the person who completed the turn in front of you. But even with that.... the disc may win, I'm not sure.

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Ed O'Malley
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Trackies all ride discs, all the time, even for "criterium-ish" races like the points race. but the effective lean angle is less due to the banked track, and a smoother surface... hmmm.....

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If you're in a situation that without lateral flex you will significantly reduce normal force I could see that being true. And with racing motorcycles that often have to clip the kurbs when cornering side by side, it could be bad. But with the difference in flex we are talking about with these two wheels, the flex of the tire is the primary method of absorbing small bumps. The difference in flex of the two wheels is insignificant compared to the flex of the tire. If the tire can't absorb the bump, the extra flex of the wheel is not going to do it and normal force is going to decrease pretty much the same amount with either wheel.

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Ed O'Malley
www.VeloVetta.com
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Yeah I was going to mention that. Always race with a disc in the rear. It's faster. I've actually thought about doing a crit with a disc, but really don't want to deal with potential destroying a very expensive wheel. That and I get endless amount of crap for it. haha

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Heath Dotson
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