Like most things high performance, carbon fiber has its benefits and its drawbacks. Benefits, of course, include things like increased strength to weight ratio, stiffness and vibration dampening. Drawbacks include the fact that abrupt strikes, such as the forces that occur during crashes, can result in internal cracks to the structure. These cracks can cause components to ultimately fail. Unlike steel or even aluminum, these cracks can be non-obvious, and are not repairable.
Therefore it is very important that your carbon fiber parts be inspected after crashes. Of course you should always have this done by a qualified professional, as a failure of a frame, fork, bars, or other component while riding can result in serious injury or death.
I recently had such an experience (documented in high-definition point-of-view glory) that resulted in my FSA CarbonPro Compact bars striking the ground rather abruptly. I definitely wanted to give the bars a detailed inspection. The visible damage was fairly minor – abrasions on the tips of both brake levers, and some ripped tape. However, the very thought of the possibility of the bars failing while I was riding definitely warranted the cost of a new roll of bar tape and an hour of my time.
So of course this whole process began by stripping off the existing bar tape. In this case – because I wanted to inspect the bars both visually and by touch, I actually took the time to clean off all of the glue left over on the bars. Always be careful of any solvents around carbon fiber parts – keeping in mind that the entire part is basically a petro-chemical mold. I prefer either rubbing alcohol or a citrus-based cleaner for heavy-duty carbon degunking like this.
Interesting side note – if you look closely at the photo of the stripped bar, you’ll see something funny. Notice how that trademark “carbon fiber weave” look stops about where the bar tape started? Now why would that be? Well, the dirty little secret of carbon fiber bike parts is that in almost all case, that weave look is completely cosmetic only. Folks have become so used to carbon fiber parts looking like that they often don’t believe it is even carbon fiber unless they see it. The truth is the actual structures that give carbon fiber its strength in bike applications are pretty much never this cross over weave. That’s why it stops where the bar tape starts – you can’t see it under the bar tape, so there is no real reason to continue it down there. That carbon fiber weave has no more purpose than the painted on logos elsewhere on the bars!
So now to the actual inspection. I was looking initially for any visible lines in the material – the part should be consistently smooth and glossy over the entire bar. I actually did find one small line in the the left hand drop and employed the “thumbnail” test. The idea here is that if you drag one of your finger nails across the mark, you should not feel anything if it is just a scratch. However, if you can feel your nail “catch,” you’re probably dealing with something much more significant. In my case, I can’t feel it at all – so it is a pretty safe bet it is just a scratch, perhaps something that happened during the assembly of the bike. To check even further, I put most of my weight down in the drops. If this were an actual crack, that pressure would cause it to widen and be even more likely to catch my nail. Still no catch, so I move on.
The next technique I used involved a very specialized tool – a quarter. Carbon fiber tubing will make a distinctive tink sound when you bounce a quarter on it. However, internal cracks will actually interrupt the continuity of the carbon fibers and result in more of a dead thud type sound. My bars produced a beautiful tink from one end to the other. Literally music to my ears. Crashing is bad enough – having to drop a few hundred duckets to replace your bars is just pouring salt into the road rash.
There are a couple of benefits from being forced through this exercise. First off, this is a perfect time to get some lube on the cables coming out of the controls. Secondly, you may have noticed that the bar tape that shipped with my bike didn’t cover the top of the bars at all. Presumably this was to show off the wonderful “CarbonPro” logos that were painted there. However, it meant that casual riding on the tops meant my hands were right on the slippery, hard bare carbon. Well, I’m not nearly as motivated to make sure the logo is visible as the company was, so I’m free to extend the wrap all the way up to a more normal length. This was always something I wanted to do, but I didn’t feel justified in ripping off the perfectly good bar tape just to get it up higher. Now I’ve got my excuse.