Should I be worried?

I remember quite a while back when John had a crack in his seatpost and got pretty good advice on the extent of the damage.

Two weeks ago, I changed wheels. I have had problems with braking on the rear one since the switch, and saturday it started randomly rubbing against the chainstay, where it left a pretty huge scuff mark. I took it to Cycle Technique, they looked over the scuff mark, said it wasn’t structural, and that my rear wheel wasn’t centered. They re-dished the wheel for me this morning, and when I looked over the bike tonight, I saw a crack I hadn’t seen before:

Should I be worried ? Or can I ride the frame without concerns ?

doesn’t look good.

Your bike is carbon so this may help give you an indication of how damaged it is.
1 Take an object that will give you a nice even tone when you tap it against something that is hollow yet structurally sound (somewhat like a tuning fork).
2 Start tapping your frame every ten centimetres or so. I am quite tone deaf but If you start at a point where you know it is in good condition you should be able to pick up an ear for the sound it makes in a strong area of carbon.
3. Once you reach your area of damage the sound will change (if I’m not mistaken it should become quite dull and lower) if the tubes structural strength has been compromised. If so then It might be time to get a new frame. If not then The damage will only be that which is seen and the layers of carbon underneath are still intact. This crack though will still be something to worry about as carbon generally breaks without warning and it will be good to start planning on getting a new frame and ride with caution.
Hope this helps bro.

Hole in the frame for the internal routing is a stress riser
Looks like a crack propagated from there- so yea, I would say you should be worried
new bike time

Diagnosing the severity of CF cracks is technically very difficult even if you have access to non-destructive testing techniques, from a picture and all you’re going to get is a gut feeling response, which I wouldn’t necessarily ignore, but lets call it like it is.

But, I’d agree with Brandon’s assessment. Looks like you’ve got a crack propagating from the cable pass-through basically all the way around the chainstay.

If it was my call I’d quit riding it until I could get a handle on the damage. One thing you can try is wet-sanding off the paint layer very gently until the top weave is exposed and you can see if the crack is propagating into the top weave or not.

The sound trick only really works for identifying delamination and I wouldn’t trust it around the BB anyway.

I would say that frame is broken and you should not ride it anymore. Not to hate on CT, but they should have seen that if they were inspecting your chainstays for damage.

Verdict from CT is: Broken.
Ben: in the mechanic’s exact words: yeah, I saw your frame wasn’t stiff enough, I thought it was cracked, I looked in the normal places but didn’t see anything, I must have missed it. I just fixed the wheel because it might have been that.

I talked a bit about the problem with another CT employee when I came to pick the bike up, he told me to check my frame carefully. It took me all of 2 minutes to find a crack after cleaning the chainstays.

Do you have a lifetime guarantee on the frame?

No. They only offer a one year warranty on carbon frames.
I’m still going to send them the picture and try to get a replacement though. I’m not hoping for anything, it’s an internet reseller so their support department is probably less than stellar.