Originally Posted by
ericgu
The vast majority of manufacturers warrant their carbon frames forever, and from what I've heard, replacements are very rare - certainly more rare than steel or al frames.
A warranty doesn't help me if my frame snaps at mile 75, in the middle of nowhere.
I haven't seen any factual data or statistics to prove or disprove the claim that carbon is not (generally) as robust as metal. However, IMO there are a couple of minor problems with using carbon for unsupported 100+ mile rides:
1) As mentioned, manufacturers aren't making CF bikes that can handle wide tires and fenders
2) They also don't have rack mounts
3) Many have monostays, so you couldn't even add p-clamps for rack mounts
4) You'd have to be very careful adding a seatpost rack or p-clamps, since you could crack the CF if you apply too much torque
5) At least some CF bikes (higher-end) do not have standard seatposts, and couldn't take a seatpost rack anyway
6) Carbon may or may not fail more often than metal, but apparently it fails
faster; ergo, you have more time to notice cracks with metal frames
If you ride supported events and can frequently inspect your frame, I think you'd be fine with CF for ultras. For unsupported 200+ mile rides, I'm not sure carbon is your best choice.