While reading this question's take on the wearing out of aluminum rims used on bikes with disc brake systems, the inquiry was projected further to include carbon fiber, disc brake rims. Do carbon fiber disc brake rims ever wear out through fatigue?

Also, do the nipples have any additional support (from material other than carbon fiber) at the rim to deal with the concentrated forces there?

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    The epoxy resins used to create carbon fiber composites are degraded gradually by UV light Sep 8, 2019 at 1:47
  • Which question are you asking "Are carbon fiber rims indefatigable?" in the title or "Do the nipples have any additional support--from material other than carbon fiber--at the rim to deal with the concentrated forces there?"
    – Criggie
    Sep 8, 2019 at 4:14
  • @Criggie I guess both. Essentially, I've put into words what I was thinking as I read the q & a of which I've linked to in my question(s). If necessary, I can make two questions out of it.
    – Jeff
    Sep 8, 2019 at 5:47
  • @Jeff Its a good question. I've made a minor tweak - feel free to roll back if its not better.
    – Criggie
    Sep 8, 2019 at 6:21
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    A minor point if changing the title: I believe "indefatigable" is specific to persons, or at least to sentient beings, and it means to persist tirelessly in one's efforts. For sure, this is a relevant question about the rider of the carbon rims. But maybe it doesn't apply to the rims themselves. I think you mean: do carbon rims have a fatigue limit?
    – Weiwen Ng
    Sep 8, 2019 at 12:10

1 Answer 1


The answer seems to be that material engineers don't have a good understanding of carbon fiber composite fatigue I'm guessing because there is a wide spectrum of CFC layups using different epoxy formulations, fiber weaves and fiber/epoxy ratios. The article quoted below also says there are many failure modes for CFC whereas metal has just one: cracking.

From https://www.quora.com/How-does-carbon-fiber-CFRP-behave-in-fatigue

technically they are pretty good, better than most metals. However their fatigue resistant properties are not used by the Aerospace industry. The issue is that composite fatigue is extremely hard to predict, with results having a very wide scatter. Basically we know they are really good, but cannot confidently quantify how good.

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