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I have read in several places regarding bicycle frames that carbon fiber has a shorter life span than aluminum, and I was wondering just what would it be. I am not referring to accident-related failures of the frame. I would like to know how much would a frame hold up for a road bike if I didn't have any accidents and rode it almost 10 miles daily.

I read somewhere (sorry, can’t find the link) that carbon fiber frames will tend to crack after 4-5 years.

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    While I agree with the accepted answer, both theoretically and in practice, it is a bit disturbing to see how many of my fellows have already replaced a carbon frame due to cracking (not catastrophic). Mar 10, 2012 at 20:21

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Absent some kind of abuse or extraordinary stress (like falling on top of the bike while it's lying on the ground - stressing the tubes from the side, riding with a friend sitting on the top tube...) a carbon fiber frame should outlast the rider.

Lennard Zinn covered durability of Carbon Forks for Velo News a while back. Here are some quotes from that article in case the link breaks:

From Kestrel

For carbon forks in general, there should not be any limited life span, as carbon composites themselves are not subject to fatigue failures as metals are. So the fatigue life of a properly made carbon composite is 'infinite'.

From Look

There is no limitation because carbon has a natural flexibility. It can be used a hundred years while maintaining the same stiffness.

From Easton

The good news is the fatigue life of carbon fiber is immensely more than that of metals. While the writer expresses concern about his carbon fork lasting as long as a metal component, there is nothing to worry about in terms of fatigue life on a composite fork.

Having ridden since the early 80's I've been through this twice, once with aluminum frames and now with carbon fiber. As high end competition bikes were made of the materials there were questions of durability. Over time, as the frames became widely available, those concerns were shown to be largely baseless.

I believe most frame builders warranty carbon frames for life now. I personally know of at least two riders with carbon fiber bikes that have been ridden in excess of 100,000 miles.

That said, you should periodically inspect the frame for cracks and wear, especially at stress points like around the bottom bracket (just like you would with any frame).

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    13 years later, lifetime warranty on carbon frames is not systematic (Specialized, Trek, Cannondale, Orbea do offer it), but brands do not offer it (Cube: 3 years carbon/6 years alu, Canyon 6 years, Decathlon 5 years/lifetime (aluminium), Salsa 5 years, Pinarello 5 years,...). This lifetime warranty is often limited to the first owner, so it may be a commercial argument rather than an indicator of the long term reliability of the material.
    – Renaud
    Jan 11 at 12:36
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Carbon fiber is durable. Unfortunately, carbon frame is not just make of pure carbon fiber, but instead it makes of carbon fiber reinforced polymer - composite carbon fiber. The carbon fiber may withstand the test of time, but the polymer is subject to degradation.

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    Okay - so what's the lifespan of CF compared to Aluminium? Your statements are fine but you fail to answer OP's question.
    – Criggie
    Jul 4, 2016 at 22:10
  • By polymer, did you mean the epoxy? Also, can you say what causes the epoxy to degrade? The question does ask about degradation under sub-threshold load cycles. So, mechanical failure, but not caused by a physical strike.
    – Weiwen Ng
    Jan 11 at 12:10

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