Hi all.
I just recently noticed this mark on my carbon frame road bike bottom bracket shell and was wondering what you all think of it, is it a crack in the carbon?

We haven't had one of these posts in a while.

[Looks like the paint cracked. You should probably spend less time examining your bike and more time riding it.]

Looks like just the paint to me also. But for a definitive answer, you should ask someone at a bike shop that you trust that can look at it in person.

Also realize that the frame might be covered by a warranty if the BB shell is in fact cracked.

It was a scratch!

It’s just a flesh wound.

Probably damage to the carbon. I’d have it checked. I have a similar effect on a bike I only use on a trainer now (think it happened before but maybe that caused it)

Despite the silly Seinfeld reference above, I do want to suggest that based on the picture it looks like only the paint is involved, but you probably want an experienced mechanic or bike shop to at least look at it carefully to confirm.

Looks like the BB shell flexed and cracked the paint. The question remains - what's under the paint, i.e. did the shell just flex... or did it crack? I'd have it inspected.

Fairly easy (for most) to remove the crankset and bottom bracket to inspect.
Personally, it looks like paint cracking to me. You can ride a scratch, but do not scratch a crack in public.

If you have enough scratch, you can buy crack.

Looks like a chain drop

Put it this way probably just a scratch but there is no way to knowing if the carbon is compromised 100% certainty without an ultrasonic testing or scan, neither are readily available for consumers nor would a consumer really no how to administer and evaluate such tests even if they had access to the equipment.

IMO I would feel alright riding that because even if there was failure what is the most likely scenario? My guess is you would hear a lot of creaking or the bottom bracket would become unstable, by that time hopefully you visually see a crack spread and do a stop ride. Pull out the cranks and see if you can see anything from inside the BB shell

Hard to be a dropped chain on the NDS....😁

Your own chain, anyway.

Put your finger on the crack. Now step on the NDS pedal with as much weight as you can. Did it feel like the crack changed shape?

I tried this, but couldn't feel or see any movement. I guess I will keep an eye on it and or take it to a bike shop for a look.

Thanks for all your replies.

You are right lol

with that being the case I think the potential of a crack is a lot more ominous

it doesn't look like a crack or behave like a crack. If it cracked through it is unlikely to cause a crash. And if it is a crack, there isn't a lot you can do about it.

Probably someone slipped with a BB tool.

I would tend to agree but this is on the non drive side, so the biggest culprit of a chain drop can be eliminated

I think you're quoting the wrong post.

No

When did I say anything about a chain?