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Carbon rims durability - rim brake

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Carbon rims durability - rim brake

Old 02-01-19, 12:13 PM
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Boerd
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Carbon rims durability - rim brake

Looking into potentially buying a set of carbon tubulars - rim brake. Given the price for carbon toys I am wondering how long would they last on Mt Diablo (that's my playground).
I don't drag brakes (anymore) yet the kinetic energy downhill is at a different level compared to flats. (energy ~ square of the speed not linear). FYI I'm thinking Bora Ultra 50 or Fulcrum but that's not the point (I think).
Not looking to start any alloy vs carbon religious stuff nor brand A vs brand B. Just looking for other people's mileage on carbon rim brakes - especially mountain / hill climbing and descending.
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Old 02-01-19, 12:38 PM
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Originally Posted by .popcycle. View Post
One data point:

My kid trains and races on a set of Reynolds carbon rims. Rides Diablo frequently. Is a climber. ~6,000 miles a year on the road. This is his third year on the same rims.
Rim brakes - correct? (And thanks for the data point)
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Old 02-01-19, 12:49 PM
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With good brake pads (I like the Reynolds blue pads), good braking technique, keeping the rims clean, I don't think it will be an issue. Especially with tubulars. It's another story with carbon clinchers, but I don't think it's a serious problem with tubular rims.
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Old 02-01-19, 01:04 PM
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So what's the problem with carbon clinchers ?
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Old 02-01-19, 01:14 PM
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Let's not get into A vs B - I'd rather hear something like - "I use X brakes and Y rims tubular / clincher and got Z miles"... The whole point of this thread is to make sure I will get some good miles if I spend the money on carbon.
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Old 02-01-19, 01:23 PM
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It is possible to put a wear resistant band in the composite of the rim ..

Makers in aluminum at the higher end , did a plasma torch fused ceramic layer on their brake track ...

I leave the search up to you..







...
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Old 02-01-19, 01:25 PM
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I buy used, & one set gave up after a number of years, but they were pretty worn when I got them. Got my $250s worth.

Two others are going strong with multiple years of hilly riding- all carbon, tubular, rim brake, Reynolds blue pads.

Newer perform better than early generations. China carbon pretty darn good, especially tubular, being inherently more sturdy.
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Old 02-01-19, 01:33 PM
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Originally Posted by avole View Post
So what's the problem with carbon clinchers ?
This article does a good job of discussing it. https://cyclingtips.com/2017/12/carbon-clincher-safety/
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Old 02-01-19, 02:02 PM
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Although it is relatively rare, if there's any place that might produce the catastrophic conditions, it's coming down Diablo on a summer afternoon.
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Old 02-02-19, 03:32 PM
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Originally Posted by caloso View Post
Although it is relatively rare, if there's any place that might produce the catastrophic conditions, it's coming down Diablo on a summer afternoon.
Hence I'm interested in tubular... I saw plenty of people with carbon clincher downhill Mt Diablo and they have no problems. Most are riding brand names though. It is a lot more likely you fall because you lose control downhill than some actual equipment failure... My 2c. I had a bad wipe-out and it had nothing to do with the bike - just a wet patch in a corner and too much speed.
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Old 02-02-19, 04:19 PM
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Yeah, I don't want to overstate the issue. I have ridden my Williams 58 clinchers on Diablo many times with confidence.
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Old 02-03-19, 09:54 AM
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since you're in the Diablo area, find a few local guys riding Diablo on carbon rims and ask them about their rim wear! That will be much more relevant to your question.
Having said that, the latest carbon tubular rims nowadays should be no problem at all, even the chinese tubulars are good. Hell, even the latest chinese clinchers are good these days. My Easton EC90 Aero 55 tubulars barely get warm in any 5% gradient descent. In a short braking test coming down on a 10% segment dragging my brakes (mostly the front brake with a slight touch on the rear) for about 100 meters (that's a lot of brake dragging on 10% decline, coming from speed of 40 mph to a dead stop), my Easton EC90 front rim got warmer but I could still touch them and not feel like my fingers are burning. But on the older Bontrager D3 5 rim series (6 years old), now these do feel significantly hotter than the Easton, causing me to pull my fingers away after about 1 seconds of touching them. I know at least one guy who ride chinese carbon clincher rims on the same descents I mentioned above, and he no issue, he said his rims had some "Bassalt braking surface", I guess that's the latest chinese tech eh.

So yeah no problem with the latest carbon rim tech, especially brand name ones. Only exception is when descending in the heat of summer (90F+), but shhh 90F I wouldn't be climbing any mountain. But having said that, I have descended in almost 100F heat for stretches of 4 miles at 9% avg gradient (with plenty of 15-18% elbows requiring almost complete stop to make the turn)... on aluminum rims though, but no problem, but damn I almost passed out climbing in that heat, never again.

Last edited by aclinjury; 02-03-19 at 10:08 AM.
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Old 02-03-19, 10:25 AM
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What aclinjury said. I still don't expect that they have any issues, but not many people here are likely putting their rims through what you plan. Any modern carbon rim will have an extremely durable braking surface, harder in fact than aluminum. Also, they seem to have largely solved the overheating leading to catastrophic delamination issue these days with better resins. However, if you plan on climbing and descending something like Mt. Diablo frequently, you're an edge case. As acl says, talk with local riders.
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Old 02-03-19, 11:29 AM
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Originally Posted by aclinjury View Post
since you're in the Diablo area, find a few local guys riding Diablo on carbon rims and ask them about their rim wear! That will be much more relevant to your question.
Having said that, the latest carbon tubular rims nowadays should be no problem at all, even the chinese tubulars are good. Hell, even the latest chinese clinchers are good these days. My Easton EC90 Aero 55 tubulars barely get warm in any 5% gradient descent. In a short braking test coming down on a 10% segment dragging my brakes (mostly the front brake with a slight touch on the rear) for about 100 meters (that's a lot of brake dragging on 10% decline, coming from speed of 40 mph to a dead stop), my Easton EC90 front rim got warmer but I could still touch them and not feel like my fingers are burning. But on the older Bontrager D3 5 rim series (6 years old), now these do feel significantly hotter than the Easton, causing me to pull my fingers away after about 1 seconds of touching them. I know at least one guy who ride chinese carbon clincher rims on the same descents I mentioned above, and he no issue, he said his rims had some "Bassalt braking surface", I guess that's the latest chinese tech eh.

So yeah no problem with the latest carbon rim tech, especially brand name ones. Only exception is when descending in the heat of summer (90F+), but shhh 90F I wouldn't be climbing any mountain. But having said that, I have descended in almost 100F heat for stretches of 4 miles at 9% avg gradient (with plenty of 15-18% elbows requiring almost complete stop to make the turn)... on aluminum rims though, but no problem, but damn I almost passed out climbing in that heat, never again.
Will do that. Usually I only stop 1 minute at the top but I guess I can stop for longer and ask a few guys about their rim longevity. If I pay for a pair of Bora Ultra 35 tubular I'd like to know they last a few years.
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Old 02-03-19, 01:04 PM
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Diablo is big but actually not all that steep. Maybe it takes a fair amount of braking to stay under the speed limit,

but I don't think an experienced rider heats the rims much.

I've only done it a few times, but regularly ride descents that are steeper & 2/3 or 1/2 as long

& don't think about braking or rim wear.

I check rim temp once in a while. The most severe descent I come across (Coleman Valley) is a winding 1.5 miles @ 10%.

Even with careful alternating braking, that can get the rims too hot to leave your hand on.
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Old 02-03-19, 01:54 PM
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Originally Posted by Boerd View Post
Will do that. Usually I only stop 1 minute at the top but I guess I can stop for longer and ask a few guys about their rim longevity. If I pay for a pair of Bora Ultra 35 tubular I'd like to know they last a few years.
Among the carbon wheels out there, Boras ranked pretty high up there in terms of heat resistance (ie, high glass transition temperature, Tg), right up there with Lightweight wheels. And I beleive the latest Boras also have some tricked out braking surface making them even better. However, the slight downside to having a high Tg is that the carbon are a little more brittle (ie., if you crash it's more likely to shatter). But I reckon that if you're bombing downhill that fast and you crash, you're not really worrying about if your Boras will shatter now do you.
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