jppe

I took the newest set of carbon wheels on my climbing bike to the mountains yesterday. I didn't think there would be too many technical descents on the route I was going on so I figured I didn't have to worry about the rims getting too hot from braking.

It turned out there was more braking than I remembered. I went down a 5 mile descent that had grades of 8%-13%. Another descent was only about 3-4 miles but it had grades up to 15%. I braked a lot more than I remembered on the first descent.........so I stopped about half way down just to check on the rim temperature. Heck, it was just a little warm to the touch so I didn't think that was very bad at all. I've had al rims get so hot you couldn't keep your fingers on them.

The wheels climbed really, really well. I doubt I'm any faster but they are just easier to turn over which to me is a plus. As an example, I was able to do the steeper climbs in one easier gear.

I do know of a couple descents I've done where I would not be comfortable using the carbon wheels. It is about 3 miles long, averages about 10% and has tons of switchbacks. I've ridden the brakes on that descent a LOT----pulsing them almost constantly to keep speed in check. I know of riders that have overheated rims on that descent in the past.

Anyway I feel more confident that it is going to take a good bit of braking to overheat these things. However I'm still going to be pretty selective where I use them in the mountains. There will be ideal for a few rides we have in our area where there is mostly climbing and there is not as much descending. These are point to point rides that finish on top of mountains and they buss you back down.

Bill Kapaun

I built a "heavy duty" OC rim for the rear of my grocery getter.
I now find myself not wanting to use the brakes on my "expensive" rear rim!

stapfam

A lot of Tandems have problems on long descents and most of the problem is riding the brakes to keep speed down. Mine has disc brakes so the problem is less but on an evening ride the discs took on a dull orange glow. The cure that does work is not to ride the brakes and only brake when required. Let speed go up and then brake firmly till the speed gets more acceptable- then release completely. Going down the hills in this manner doesn't impress any riders following you but does keep the rims cooler.

billydonn

This bicycling is scary stuff sometimes.... eh? Coming down Gavia last week I was sure I'd worn out a set of brake blocks... it was so steep and constantly turning that I never did build up any real speed. My hands were kind of tired at the end.

Monoborracho

That you had "more braking than you remember" is probably, or possibly, indicative of the less effective braking action associated with carbon fiber brake surface.

jppe

The roads were dry and braking was outstanding---just as good as my aluminum rims. I just didn't remember the frequency of the turns that needed braking. That is probably a distinction o four NC mountain roads versus the ones I've ridden on in Colorado. Most of the descents I've done in Colorado required little braking as the roads weren't as steep and the radius of the turns was much longer in Colorado.

BikeWNC

I don't believe you. At least I choose not too because I don't want to pay out for them. BTW, I'm back from a month away in the Yukon and Alaska and have been off the bike for 5 weeks. I need these wheels just to ride the flats.

Terex

So what brand and model of wheels are they? If they have aluminum braking surfaces, even braking and minimal heat build up isn't surprising. If they are Zipp Firecrest 202 wheels, not surprising either. They are billed as climbing wheels, and you are billed a medium fortune to buy them. Older and less expensive carbon wheels have overheating and braking problems, but they're constantly improving designs.

I have a pair of older Reynolds Attacks on my Parlee, and I wouldn't go on a big climbing ride with them.

Article on braking safety from last year: https://www.bikeradar.com/gear/articl...rs-safe-34521/

Also last year, a fairly comprehensive article on utility of carbon wheels : https://cyclingtips.com.au/2012/08/wh...rbon-wheelset/

The article points out that a growing number of mass participation rides do not allow carbon wheels due to increase rate of failure over more traditional wheel sets. And note embedded article from Red Kite Prayer.