Originally Posted by
Homeyba
I've broken steel frames, aluminum frames and titanium frames but never a carbon frame. That doesn't mean carbon will not break because it can too. The difference is that carbon failures are almost always a result of damage caused by something other than wear (I've personally have never seen a fatigue failure with carbon). Any high end frame should last, doesn't matter the material. Sometimes things just happen. That's what warranties are for.
My understanding is that steel and titanium do not fatigue if the stress is below their limits. Aluminum does and CF does. Additionally CF can be affected by things like sunlight, scratches to the clear and UV radiation. I have personally seen far more carbon forks and frames cracked than steel or QUALITY ti.
So if your ti/steel frames cracked it was either due to something catastrophic or manufacture failure. It might be that in the practical course of life cycle fatigue is hypothetical and damage is more likely due to manufacture failure and some material has more risk due to manufacture difficulty (ti and some steels).