RShantz

I recently got a set of 50mm carbon clinchers and took them to the mountains for the first time this weekend. I thought the braking was just fine, and I was just as fast if not faster on the descents that what I was on my alum clinchers. What we call mountains around here are only 4-6 miles.

What are the specifics to folks that overheat their carbon rims on descents? I only brake right before I enter the turn and then try to haul to the next turn. Are folks braking the whole ride down and thus overheating? Or are they riding like I do, but have much longer descents. I felt the rims at the bottom and couldn't tell any real heat build up.

I'm really asking b/c some of the local mountain events say/suggest no carbon clinchers when you sign up, and I've got to decide if I'm going to listen to that warning. Almost all of my buddies that have carbon clinchers take them to the events but they don't ride the brakes going down the mts either.

KantoBoy

First and foremost, listen to them. This is also a precaution in case it rains. Not everyone descends like Contador, Nibali, Bardet or Sagan.

Whatever you do, don't grab a handful. It's the best way to warp a rim and it doesn't matter what brand it is.

...and if someone here wants to argue that pros do it, it's because they have a full Fn service course full of carbon wheels at their disposal.

gsa103

Larger riders, who ride the brakes will have issues. Light rider going fast, will be fine. For an event organizer, they simply don't want to deal with people not knowing limits.

At one point, I did an interesting calculation. For a fixed 6% downgrade, 18 mph is the absolute worst speed you can go in terms of heating your rims. Going faster means more aero-drag and less braking. Going slower means that you don't descent as fast so the you don't need to bleed as much speed.

Of course, inexperienced descenders frequently ride the brakes in the 15-20mph range, which puts a lot of stress on rim heating.

gregf83 

Steeper descents with more hairpin corners will heat your brakes. We have a local climb, about 800m and 6.8% that only has a few hairn corners and you can pretty much descend the whole way without braking. I'm sure other hills with steeper grades and sharper corners would be more of a challenge to the braking system.