CPT Chaos wrote:
Except for one thing, that descent hardly required any braking for a skilled rider.
I'll agree with that, but you also don't hug the brakes until you're doing <15mph on a steep downhill unless you are unconfident in your brakes, which is the case with people riding their carbon rims for the first or near-first times on a big downhill which is 10x more likely than people being just so scared that they're doing <12mph on a twisty downhill.
Even my 8-year old daughter who doesn't even like riding fast can take a curvy downhill over 15mph on a kids bike, so I'd say that it's more likely that these riders on that IM course, while lacking good descent skills yes, were farrrrrr more limited by unexpected equipment limitations. Even when I've ridden with totally-retired non-racing casual bicyclists on charity rides, they can take the descents at a surprisingly fast pace.
I once swapped out my brakes for an markedly inferior one (I didn't know it would be that inferior at the time - but it was cheap!) and while it worked ok on flats, I was horrified on a 8% downhill that I was barely able to stop once I was over 17mph. I took that descent at under 10mph, and I'm a pretty confident descender (I'd go over 2x as fast with ultegra brakes). That's what you're dealing with.
I know people should absolutely hard-test their equipment before race day, but I think a lot of folks don't bust out their race wheels with the carbon-type brake surfaces on truly big descents as much as they should before attempting it in a race situation.