Bonesbrigade wrote:
I loved the second podcast on asymmetry. I have a question for you though: Going back to your testing at Roubaix on the cobbles, you guys kept lowering the pressure and the times got faster every time you did so until you broke the wheels. I'm wondering why at that point you didn't switch to larger volume tires and repeat the same test? It sounds like lower pressure wasn't explored further due to the tire size limitation (bottoming out) and not actually reaching your inflection point.
Did you not use larger tires because:
Was it because you were already using the max tire that would fit on the bike?
Already using max tire size from the sponsor at the time?
Or already conducted an aero/rolling resistance weighted analysis to determine the optimal speed when factoring the course as a whole?
Did you conduct your own analysis with larger tires just for your own research for a later date?
Thanks Josh!
-Iain
So the time context here is pretty fun... in 2007-2009 when we were really pushing hard to understand the problem, the belief amongst the riders was still that the 24mm tire was faster in the dry and 27 was only good in the wet because it was 'slow'. We also had to contend with the bikes of the time, none of which could really handle more than a 27 or 28mm tubular tire (so measuring ~28mm)..and sadly we haven't been that much better off as of late as I think about it!
So way back then we figured pretty quickly that the 27mm Vittoria that the team had access to was faster on the cobbles than the 24 AND safer regardless of wheel.. so at that point we realized that a good part of the solution here was going to be educating the riders and convincing them to ride the bigger tires. There is a photo on the internet of me with Bjarne and Cancellara in the LSWT in San Diego, and the whole point of that entire test was to put him on a road bike and show the benefits of the aero wheels over the traditional classics wheels and to then show that the added drag of the 27mm tire wasn't that bad, while we did field testing on Crr to show them that the 27mm tire had same or better Crr (which they were all conditioned to believe wasn't true.. wider is higher Crr was the firm belief). I'd estimate that we spent probably 20% of the Roubaix project time doing things to help with rider education and psychology about all of this as the pushback was just so strong.
So yes, we were using max tire that would fit the bike, which was also the max tire size made by the sponsor.
The whole 303 super-toroidal design came about in 2009 from this.. once we settled on the 27/28mm tire we had to design a wheel around it to minimize the aero penalty as it was somewhat significant on the 24mm wide 303 and 404 rims of the era.. and those had previously been considered to be 'wide'.
It would really only be 2012 or so before the bike manufacturers started to catch up with these changes... painful for us at Zipp, the Specialized Tarmac launched the year of the first Roubaix win (2010) could not fit 28mm tires or the 28mm wide 303 rim, even if it had a smaller tire as they had bulged the chain stays inward seeking stiffness.. so looking back it seems like this just happened, but it was really a pretty significant battle for a few years there to get this to change.
In the last 5 years the limiting factor has continued to be the frames and rim brakes... I've been involved with 7 of the last 8 Roubaix winners and all 5 of them since buying SILCA, and the challenge has been finding ways to get 30mm tires into the bikes and/or the brakes.. so you can extend dropouts and things like that, but then you need long reach brakes or offset brake bolts.. we've seen it all. Last year Peter Sagan won on a very custom bike with tires labelled '28mm' and measuring just under 30mm stuffed into some 'tuned' DA rim brakes... Ideally we get them onto disc brakes and the sponsors making 34-35mm wide rims that can be solidly aero with 32mm tires..
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