Bicycle Mechanics - crack on carbon wheelset
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03-28-08, 03:42 PM
I've made a small crack on upper tip of sidewall while mounting a tubular tire.
I accidentally hit the ground with the rim and it caused a crack about .5mm wide and 1.5 ~ 2mm deep.
Im just freaking out because this was purchased just couple of days ago and never even ridden.
Is this something I should forget about or fix before riding? If I do need to fix it how do I?
spec : Cervelo soloist with Planet X pro carbon 50 wheelset
03-28-08, 03:49 PM
This doesn't sound good to me. Can you replace the rim?
03-28-08, 09:55 PM
Planet X may be willing to warrantee it for you!
03-28-08, 10:07 PM
A crack or a chip? If you fumbled and dropped it from just a short height or it's from pressure against a hard floor to cause this I'd say that you just chipped out the outer clear coat. The key will be to carefully study the crack and see if it has broken any of the fibers.
If it is just a chip out of the clear coat a little dab of any good quality clear epoxy will fix it up just fine. You aren't repairing it in this case as much as you're just sealing out any water or other contaminants from getting into the fibers below.
If it is a crack that extends into some broken fibers you may need to return it to the maker for an assessment. Carbon anythings are like a big spiderweb where the integrity of the web relies on each and every strand doing the right job. Breaking a few of those strands in the wrong spot is like a small crack in a car's windshield. It'll be fine until stresses start flowing through the glass and then the crack acts as a stress concentration point and the crack grows fast from there.
So study it carefully and assess the power of the drop. Remember that these are wheels so they need to be pretty tough in the first place. If you didn't really drop them from far it's much more likely that it's just a clear coat crack or chip. Especially if it is just from pressure against the hard floor during the tire mounting.
Hint, keep a carpet floor mat ready for next time.
03-29-08, 01:19 AM
Thanks all for your reply. I'll inspect carefully whether it's just a clear coat crack from mounting a tire.
Anyway I didn't know that the caron is so weak as this and I've learned my lesson. I'll be carefule going forward !
03-29-08, 03:07 AM
The carbon itself is actually darned tough. It's the epoxy it is embedded in that isn't all that strong. In the composite mix it's amazing stuff. But on it's own like in a top coat the resin is not any stronger or more flexible than the plastics you find many cheap toys made from. But when it comes to the overall bending loads encountered from riding they are superbly strong and resilieint because the forces are spread out through the wheel in a predictable and designed for manner.
The key is to do whatever it takes to avoid point loads such as the pressure point that is generated when you push it against a hard surface like a floor. It's probably why I've also seem pictures of well padded wheel bags for transporting them separate from the bike itself while some cheap spoked "frame protectors" are put on for transporting.
03-29-08, 02:19 PM
Hi BC rider,
Thanks for your details. I would like to take the picture for you to see but I already mounted the
tire over the crack ( or chip ) .
I have one question . How do you know whether it's just a chip or crack??
03-29-08, 03:48 PM
Without seeing it or showing it to someone that knows their composites it's hard to say. Flexing the wheel slightly while looking at the damage can tell you a lot.
If you know where the damage is I'd mark the area with a little dab of something that won't wash off. Even just a little "dart" of clear adhesive tape. Then keep a close eye on the area for any signs of the crack growning outside and to where you can see it
03-30-08, 08:55 AM
Hi BC rider,
Thanks for your reply. I'll get the point and I'll do as such.
Thanks and have a nice day,
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