Occasional clunk in BB. Campagnolo content

[Cicli]

I get a clunk or thump about every few revolutions. Nit really consistent. I am running the black u/t cups and read somewhere they are looser.
Campagnolo people, would it be worth a shot to try the greenish ones before I hunt further? Chainrings are tight and no issues with the chain.
Thoughts?

[oldpotatoe]

Originally Posted by Cicli

I get a clunk or thump about every few revolutions. Nit really consistent. I am running the black u/t cups and read somewhere they are looser.
Campagnolo people, would it be worth a shot to try the greenish ones before I hunt further? Chainrings are tight and no issues with the chain.
Thoughts?

Black don't have seals..but the 'tolerances' are the same as the greenish ones.

Which rear wheel? mavic by chance?

[Mark McM]

It may not be the BB. BB noises typically occur at a rate of once (sometimes twice) per crank revolution. Clunks/thunks that occur every 2nd or 3rd revolution of the crank are more typically chain issues. Another indication of chain issues is if the frequency changes between big and little rings(chains are about 104 links, so they cycle through the drive train once for every 2 crank revolutions with a 52t chainring, and about once for every 3 revolutions with a 36 tooth chainring). If this is the case, check for stuck or bent chain links. If the chain has a lot of wear, also check the quick link, as these often wear a different rate, and can cause 'thunk' as it engages the chainring with a different chain pitch.

[gfk_velo]

I'd take a careful look at the chain, first, and make sure that you don't have a link trying to "open" - that's not only the cause of an annoying noise but obviously a big safety issue.

Joining link not fully closed? Joining link about to fail (seen that a good few times) ...

Very worn chain? Have a look for a damaged or failed roller.

Try swapping the rear wheel out - it could be a cassette body issue.

Swap the pedals out - could be a slack pedal bearing (though usually that's a more regular, once or twice per rev issue).

Then, as MarkMcM suggested, look at chainring teeth.

Unlikely to be a BB issue unless the bearings are toast - but again as MarkMcM pointed out, that tends to be once or twice per pedal rev.

[duff_duffy]

Does it happen on both chainrings? I bought a used bike that had similar problem on just the small chainring and turned out to be one of teeth was bent at tip and it would just slightly catch the chain a bit as it went around. Just filed it a bit and all was good.

[stackie]

I was getting a thunk that I was sure from BB, usually when slow cadence climbing. wound up replacing shoes and cleats. Noise disappeared. Just one data point

FWIW

Jon