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Bike Tech, Fit Tech and GPS News & Discussions - Exploding Carbon Clinchers

webgeek - Dec 24, 2017 - 10:17 PM
Post subject: Exploding Carbon Clinchers
Interesting video as I've wondered carbon wheels with rim brakes.
Of course, I'm not sure what these tests mean, other than you can overheat the carbon wheels catastrophically.
What this amount of braking and temps equate to in the real world is not clear from these tests.
Not likely that we'd encounter this locally, with something like 300sec of continuous braking.

https://www.youtube.com/watch?time_continue=2&v=OlZvFPdLulI
forrest - Dec 25, 2017 - 10:51 PM
Post subject:
300 seconds of continuous breaking isn't hard to do coming down Brasstown.

Catastrophic failure is EXACTLY why I avoid graphite rims. It is a good justification to stick with metal frames as well.
TimH - Dec 26, 2017 - 02:06 AM
Post subject:
https://www.youtube.com/watch?v=VfjjiHGuHoc
forrest - Dec 27, 2017 - 01:24 AM
Post subject:
That is exactly what will happen after enough cycles.

I was looking at some of the testing that one of the major manufacturers was boasting about a few years ago. They were showing how everyone else's fork would break but theirs wouldn't under the controlled conditions. I would not want to ride on any fork after, say, a piano or anvil were dropped on it and it survived. The catastrophic failure could be seconds or months away, and it is hard to conclude anything from nondestructive tests.

In auto racing, composite roll cages are generally forbidden. Your chances of surviving a wreck are better if your cage bends than if it snaps.
TimH - Dec 27, 2017 - 04:07 AM
Post subject:
forrest, didn't you have a carbon bike break a while back?

You went down on wooden bridge in the wet or something?
forrest - Dec 29, 2017 - 07:36 AM
Post subject:
Yes, I was on the bridge that goes over Rottenwood Creek. You have a good memory.

I slipped at about 5 mph, and the bike just went sideways. The frame twisted around my legs as I landed on my side, and the seat stay broke. There was no impact damage whatsoever, and the seat stay didn't touch anything. I noticed a ride or two later that the composite was split in several places running for a few inches along the length of the stay. I wouldn't be surprised if I damaged the top tube as well. That seems to be a common point of failure on some of the Orbea frames, and I broke that part in a similar manner with no direct impact damage on my Hogpen wreck.
TimH - Dec 29, 2017 - 07:52 PM
Post subject:
Can't say I blame you for not liking crabon and what you describe is one reason why I chose a Niner for gravel.

The RLT 9 RDO is essentially a road bike but the carbon layup (schedule) is done like a mountain bike. A tad heavier than a road frame but very robust.


-Tim-
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