redfooj

bottom bracket... area looks thick and stiff... dont think this dislocation point (under the tape) is bad enough to grow and deform ... but i could be wrong

gsteinb

Lbs

Dagamon

That's a mountain bike. We don't have that kind of expertise here.

warningfs

Those fat tires scare me, I dont understand them

waterrockets 

+1

Let them tell you what it's about.

It would be better to show it without the tape covering it! I'd be tempted to drill small holes in the ends of the crack to prevent spreading, but only as a last resort.

Brian Ratliff

I believe cracks are self-terminating in fiber reinforced plastic composites; in other words, the crack will not spread due to fatigue - doesn't mean it won't unzipper (means just like it sounds) catastrophically under heavy overload. Drilling the crack ends are usually to prevent fatigue propagation in metals. While you are relieving the stress concentration, you are losing material and I'm not sure that's a good thing to prevent a catastrophic failure. But again, we are all looking at a picture; if the OP can't come to the decision on his own to ride it or not, best to send it to a qualified bike shop. Might send the picture to a composite's shop like Calfee who has experience evaluating these things. With a crack like that in that area, there might be more damage in the carbon fiber structure that is not visible.

For what it's worth, even if the frame fails catastrophically at that location, I don't think it would result in a catastrophic crash or anything. I might ride it with that consideration alone, but that's just me.

StanSeven

Maybe the tape keeps it from cracking more

curiouskid55

tap the area with a quarter . if you hear clicks you are golden. if you here any clunks you are f****d. what is the tape for?

surreycrv 

A crack will continue to propagate in a FRP structure. the hole drilling technique is a cross over from metal workers ( and not recommended for plastics). To keep the region from further stress, it's really easy, apply an epoxy topcoat using some form of fibre for reinforcement. could be carbon, or even an e glass 6 or 10 oz cloth would be sufficient.

Now if aesthetics are top priority, then the region must be scarfed first, then the patch overlay applied and then faired smooth. but its on the bottom, patch it and ride.

waterrockets 

Interesting from both posts. I was thinking about it on a lunch-ride climb today. If I take an FRP like paper and put two parallel tears into it, then punch a hole in the bottom tear, if I pull across both tears, which one will fail first? I got back and tried it three times, and each time, the hole failed first. I don't have a hole punch, so I cut a hole with scissors, but they were all pretty smooth (half-folded, cut, unfolded).

So, yeah, doesn't seem to help with fiber stuff

Looking at the bottom of the BB shell though, there is a hole in it already. Any thoughts as to if that was drilled at the factory, or molded in?

ahsposo 

I think that will buff right out.

surreycrv 

the hole is to drain any liquid that could get in the frame

Bacciagalupe

I second the idea to take it to an LBS, and have them check it.

dtrain

OP - are you the original owner? That is a Trek, correct?

zazenzach

pseudoscience