Descending with carbon clincher still an issue?

[spdntrxi]

I know two guys that have warped rims. Both are nearly 200 lbs. One wheel set was Reynolds and other was Enve (old brake track) both happen on Bohnman in NorCal. I'm not that might either but have managed ok with old and now new Enves


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[LionelB]

Blowing out on Meyers grade is weird, you are not using your brakes a whole lot on this if you know how to designed half decently.

[albertop07]

It would be interesting to get some data from this forum on who has melted a rim, what rim, and the circumstances, rider weight and so on

It's not generally something people come on forums and own up to precisely because it's associated with poor technique

I live in Rio de Janeiro and for those who have seen the Olympics on TV I ride a lot on the Vista Chinesa descent (lots of falls there during Rio2016 Road Race). That descent is steep and slow (12% average with lots of low speed bends). And Rio is really hot during summer. So that is a pretty good lab for descending on Carbon Wheels. I am 175lbs so not light, but not too heavy. And I do alternate braking during descend (where it is possible).

I broke DT, 3T and some Chinese (all tubulars) there. Got warranty on 3T and DT. Tried some Chinese (Carbon Speed Cycle from eBay) clinchers but they last 2 descends. I am using Zipp for 2 years with no issues (202 and 404 tubulars). Also used Vittoria Graphene and they work fine. Lightweight (Meilenstein) are also OK. All those wheels are tubalars, I don’t trust clinchers today on that particular descend.

I have a friend using Bontrager Aelos 3 TLR and they are OK so far. He is using then tubeless and he is like 170lbs.

[kulivontot]

I feel like the kind of people who buy carbon clinchers are also the kind of people who buy disc brake road bikes, so is this even relevant anymore?

[eaglejackson]

Blowing out on Meyers grade is weird, you are not using your brakes a whole lot on this if you know how to designed half decently.

I generally agree but with a lot of riders on the course and speed increasing as you descend, many riders were braking to slow down and keep speed under control. You can come up very fast on someone ahead of you riding more slowly. If you're descending freely on Meyers Grade you can hit some very high speeds. I heard Andrew Talansky that day -- riding at the front of course -- hit >55mph on Meyers Grade. And no doubt there is some bad technique, applying light amount but extended pressure on the brakes, heating up the rims in the process. All said, there were lots of blowouts on Meyers Grade, including my friend, an experienced rider.

Hauser Bridge is a steep technical descent and that's more understandable why there were LOTS of blowouts there.

I can't say they were all carbon clincher rims but it sure was an eye opener to me. I was glad I was on aluminum rimmed C24's and had no issues.

[Kayrehn]

Wow, good thing you trust tubulars more. Sounds pretty scary, but I guess you only discover the wheels failed after the descents rather than them collapsing catastrophically mid ride?

[albertop07]

Wow, good thing you trust tubulars more. Sounds pretty scary, but I guess you only discover the wheels failed after the descents rather than them collapsing catastrophically mid ride?

Correct. All of then started with faults on the brake tracks. Even the clinchers did not collapse. The braking surface melts and then the carbon begins to crack. They start braking like the wheels are not true. But don't forget that is the worst case for carbon rims: steep, slow and hot.

[sawyer]

I haven't melted a rim or anything like that, but I've certainly stopped on a descent when I knew damn well that my rims had to be burning hot and I was getting worried about the clincher just blowing off of them. Not even carbon rims, but alloy Campagnolo Neutron Clinchers. I'm glad I stopped because those rims were on fire. If I had been on carbon clinchers I would have been even more worried about the resins getting soft and the clincher blowing off even sooner.

What I'd like to know about people's experience with carbon rims, is whether anyone has actually worn through the brake track, not due to heat or melting or anything, just from normal wear, as would ultimately happen to an alloy rim. I find that carbon is much much harder than aluminum, and to date I have not seen a carbon rim that has worn through like that. Yet people are so afraid of damaging them in the rain or whatever, like they're made of some super fragile material. My guess is that an alloy rim will wear out much faster through normal wear and tear than a carbon rim would.

I'd agree with all of that Calnago

I've stopped for precautionary reasons on alloy clinchers in the heat in mountains. Never ridden carbon clinchers in the mountains and am not keen

Tubs feel so much safer in those riding conditions

[LionelB]

I generally agree but with a lot of riders on the course and speed increasing as you descend, many riders were braking to slow down and keep speed under control. You can come up very fast on someone ahead of you riding more slowly. If you're descending freely on Meyers Grade you can hit some very high speeds. I heard Andrew Talansky that day -- riding at the front of course -- hit >55mph on Meyers Grade. And no doubt there is some bad technique, applying light amount but extended pressure on the brakes, heating up the rims in the process. All said, there were lots of blowouts on Meyers Grade, including my friend, an experienced rider.

Hauser Bridge is a steep technical descent and that's more understandable why there were LOTS of blowouts there.

I can't say they were all carbon clincher rims but it sure was an eye opener to me. I was glad I was on aluminum rimmed C24's and had no issues.

Yeah maybe, I did this fondo twice on my Bora 35 tubs, never even thought a minute about this. I'd never ride carbon clincher anyway, I barely ride aluminum clincher. Tubular are fundamentally safer. I did blow a rear clincher tire out decades ago on a mavic clincher, that crash made me a life time convert to tubs.

[MoPho]

Not necessarily safer on Tubs
http://www.cyclingnews.com/news/tour-de ... ular-glue/



.

[LionelB]

Yes it is a lot safer on properly installed and glued tubs despite the inter web infested by the Beloki crash etc...

[Wormiez]

Why would Tubulars be considered safer then Clinchers for hills?

[sawyer]

Yes it is a lot safer on properly installed and glued tubs despite the inter web infested by the Beloki crash etc...

LOL - very true. Beloki was getting a bit long in the tooth at 12 or 13 years old so that tub roll must have been a godsend!

My money is on mechanics getting it wrong and / or low pressure in these scenarios. Otherwise why are 99.999% of mountain descents by pros in the heat done without rolling tubs? It's specific factors at work, probably not poor technique given it's pros involved ...

[McGilli]

Not a 100% these were on a descent or not, but after seeing tons of flat tires, blown tubes, and other questionable wheels from Levi's GranFondo, I'm don't think I'll ever be sold on carbon clinchers.

You can't base this sort of thing on people who ride a Fondo. The reason being that any joe blow can pay the money - and join in. They can have absolutely zero cycling skill - let alone descending skill. We have the Whistler Gran Fondo here every September- and like clockwork - middle of August - you see a few hundred cyclists that you have never seen before all year all of a sudden out for a ride on their shiny new bikes and their corporate team jerseys.

[Calnago]

In general, not even talking about hills, when/if you do get a puncture at speed, the leak on a tubular 1) is usually slow which allows you to come to a more controlled stop and 2) because it is securely glued to the rim, it doesn't pop off instantly like a clincher can and will under the same conditions.
Also, because the tube inside the tubular is fully encased by the tire itself, it cannot escape. With a clincher, if the tube gets pinched between the tire and rim, and it blows, it's usually a big bang and blows the clincher bead right off the rim. And tubulars are not nearly as prone to pinch flats as clinchers.
Now when you throw hills into the mix, you have braking forces generating large amounts of heat in the braking surface. While the resins can get hot in either a carbon clincher or a tubular, the clincher brake track has the much higher force on it from the high pressure clincher wanting to push it apart (the tubular is contained in the tire casing and only exerts a downward force into the rim bed. When the resins in a clincher sidewall get hot enough, the pressure from a clincher tire can push the softened sidewalls apart and boom... off pops the clincher, not to mentioned a ruined rim. And possibly much worse.


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