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The wheel that may have lost the Giro
What actually caused Hamilton's crash?
The image of Tyler Hamilton crashing at the bottom of a key descentas the Giro d’Italia’s other main contenders is firmly emblazoned inthe minds of anyone watching OLN’s coverage and saw that loop of tape played over and over. Coming through a turn, Hamilton stood up onhis pedals and suddenly lurches forward and hits the ground.
Hamilton stated in his diaryon velonews.com that the freehub had not engaged when he stood on thepedals, causing the crash. The pain he had to deal with with over the remainderof the Giro is well documented, as is the amount of time he lost on mountaintopfinishes afterward – probably well in excess of the amount by whichhe lost the race to Paolo Savoldelli (Alexia). The impact of the crashbecame even more apparent after the race when doctors discovered the CSCteam leader had actually broken his shoulder in the crash.
So what happened?
Well, clearly it was the wheel's fault. But who made the wheel?
To start, the wheel Hamilton was riding was not one from the team’swheel sponsor, Shimano. Rather, he was using a superlight all-carbon ADAwheel from the Netherlands. Indeed, it turns out he was using preciselythe same wheel CSC-Tiscali team director, Bjarne Riis used in his successful1996 conquest of the Tour de France. It had been built for an eight-speedShimano cogset but was now holding a 9-speed Shimano cogset for Hamilton.
According to ADA owner Cees Beers, Hamilton’s wheel had ADA’s old pawlsystem inside, which ADA changed a few years ago because of concerns aboutengagement problems like Hamilton experienced.
“The old system had six pawls, but some people left out three of thepawls because of the friction, which is what had been done with this wheel,"Beers told VeloNews. "With three pawls, it did not provide enoughsecurity. Since the three pawls are arranged equidistant from each otheraround the axle, if one pawl doesn’t engage, then less than one half (aboutone third, in fact) of the circumference of the freehub is engaged, leavingit vulnerable to breaking free. Furthermore, the pawls were further fromthe bearings in the old system, making it more possible to distort thefreehub enough for a pawl to skip. In our new system, we have only threepawls, but they engage more deeply, and distortion is minimized by thebearings being close to the pawls.”
Beers said he spent hours watching the now-infamous video.
“Hamilton had just shifted on the downhill, and it looked to me likethe chain was not engaging the cog quite right as he took 3-4 pedal strokeswithout pressure before he stood up out of the corner," Beers said. "Beingin the smallest, 9th cog at the greatest distance from the pawls and bearings,the combination of the chain skipping and suddenly engaging while he appliedhigh pressure out of the saddle caused the freehub shell to distort. Ithink the shell became eccentric enough that one pawl missed its tooth.With the high pressure on the pedals and only a third of the freehub engaged,the other pawls jumped out as well, causing the crash.”
“I had been recommending for some time that people with the old wheelsshould make sure they use all six pawls in them, which I think would haveprevented this problem. Because of an illness in my family, I was not ableto make the new wheels Bjarne Riis had ordered for the Giro, so they usedsome of his old ones. After Hamilton’s crash, I repaired all of the team’sADA wheels by putting six pawls in each and checked them out completelyto make sure they are good. I never want anyone to get hurt on my stuff.If it’s my fault, I will be truthful and say exactly what happened. Butanyone with old ADA wheels with three pawls in the freehub should put sixpawls in them or send them back to me so I can do it.”
Hamilton had no further wheel troubles during the Giro – as long ashe kept the rubber side of them down, at least.
