Should I worry about a chipped carbon mountain bike frame?

Question

The other day while I was racing my Specialized Stumpjumper I noticed a chip on the frame. It's on the rear support bar right behind the seat post between the rear tire.

My teammate who is a mechanic said its just outer damage, they tapped along the frame without hearing a change in pitch. Others agreed. I brought it into the bike shop the next day and they said that I shouldn't ride the bike and were willing to sell me a new frame. Are they just trying to get money out of me or is it really cracked?

Answer 1

The problem is liability. Any shop is likely to tell replace as they don't want the liability of it breaking and you getting hurt. Plus they want to sell you new frame.

I would go with your team mate the mechanic.

See if it grows. Even if it does fracture and you fall I bet it will not be your first fall nor fatal.

Answer 2

Cabon fiber has evolved a lot and, contrary to some retro-grouch hysteria, is actually really tough. Don't worry about a chip. Even if it went through the paint and took a nick of carbon fiber out, you're fine.

The seatstay especially is a part of the bike where you won't have to agonize over it. If you flat out broke a seatstay, it wouldn't put you over the bars or anything crazy. A nick is nothing, and you've had a mechanic look at it.

Here's a dude wailing on a carbon fiber fork with a big steel hammer:

https://youtu.be/6QNRpSkTGoA

Answer 3

The worry here is that what seems like a simple ding on the outside could have caused some delamination of the frame on the inside, which in turn would cause weakness.

In general, a structurally intact laminated frame tube will make a clicking noise if you tap it with a coin. It should sound the same along the full length of the tube. A damaged one will usually make a duller thud. Notice I said in "in general" and "usually". This method is not an exact science and is no substitue for proper analysis if you are really concerned about it.

This next advice may not be useful for your seatstay scenario, but if it is a larger tube you can get access at you could try to take a look inside with an Inspection Camera.

Other than that, if you really want to be sure then it needs better analysis by a professional. Possibly an x-ray.

If it is badly damaged enough that it should not be ridden, you might not even need a new frame. Carbon frames can be repaired.

That being said, for what sounds like just a minor chip I'd go with your mechanic friend's advice and just keep an eye on it. Like Frisbee said, the bike shop is probably worried about liabililty. If it was the fork/downtube/toptube rather than a seatstay I'd be more concerned. If they fail it's not just your frame that will end up cracked. You'll likely have some cracked bones and teeth too.

Answer 4

I cracked my Mountain Bike carbon frame last year. It was replaced under warranty. You could see a visible crack. I also have a Carbon Road bike that I have crashed a few times and has a major paint chip out of it, but is still structurally sound. If the frame still feels solid in the area of the paint chip it is probably ok, and the damage is just cosmetic.