Originally Posted by
Wogster
The problem with CF is that there are some dishonest sellers out there. One problem with Trek, from what I understand is that they warranty their CF frames for life, but you need to pay the dealer to transfer the components over to the new frame. This can cost a couple hundred bucks, and the guy figures he can sell the old one for a good price, put $400 into it and get a whole new bicycle. So they fix the old bike up so that it looks good, and sell it. They recommend replacing the frame because the only way to sometimes see damage is to strip it and then used industrial Xray to see what is happening under the surface. This costs more then to simply replace the frame.
CF that fails because it's damaged, tends to suffer a cascade failure, some of the fibres are broken and that reduces the over all strength, which puts stress on the remaining fibres, which causes some of them to break, which puts more stress on the remaining fibres, which causes some of them to break, and eventually they all break and while the epoxy is strong stuff, it's no where near strong enough. From the beginning of the failure until complete failure can be under a second.
Now, if you know the person who has the bike and know it's history and that it's never been crashed, you should be okay, if you don't know the person who has it, and whether it's been crashed, then your better to avoid it.
Underlined for reference, not because I in any way agree.
These are true for most materials, not just carbon fibre. Corrosion, stress cracks, etc plague aluminium, steel and other structural materials. On the other hand, from experience, carbon fibre tends not to hide significant structural faults.
The underlined is true UNLESS you or someone you trust can properly evaluate the machine. Carbon fibre is not some miracle material. Nor, is is some weird, mysterious spirit incarnation just waiting to spring some surprise on the unsuspecting like a horror movie monster in the bushes.
Don't need to do anything special when buying this machine you shouldn't do with any other. In short, if it looks good and works correctly it is good to go. If it has a readily apparent fault think about it. If you can't properly evaluate the machine hire someone you trust to do so. If it looks bad, you get bad vibes from the owner, it doesn't work correctly, etc. move on to something else. Nothing mysterious about this process as it applies to just about anything a person buys.