Clicking/grinding noise in middle gear only

[sushiboy]

Hi,

My carbon road bike has developed an odd, definite click-click (say 3-4 clicks per crank revolution) from the either the cassette (I think, or from that area at least, maybe rear derailleur) or BB under moderate to high load/acceleration.

Odd thing is - it happens only in one gear (smack in the middle of the cassette range - not the largest or smallest). Changing up or down one gear and the clicking disappears. Does not seem to be chain scraping on anything, as it's not that kinda noise - and under low load it disappears in the gear in question. Happens on small and large chain ring, and only in that gear. I do run in this gear quite a bit, hence the problem.

Strange.

The groupset is Campag Veloce. Gear changes are smooth, and there appear to be no other problems. Spokes look ok, wheel is true. Can anyone give me some tips where I should start looking?

Chain is in good nick, as are derailleur gearwheels. Drivetrain is clean, not in need of lube either.

Bike has been back to the LBS for adjustment, they could not find anything. The noise did disappear for a couple 30km rides, but now it's back and a little worse.

Can you provide any tips or suggestions on what this could be?

Cheers,

Sushi

[DaveM]

First check that crankarms and pedals are on tight and threads are greased. It would be odd that either of these would only make sound in a particular gear. But they are common sources of this kind of sound and may indicate something is loose.

But if it really is just in that gear and it's not a derailleur adjustment issue, I'd pull the cassette and inspect. Wear wouldn't normally cause a noise like that. But maybe a cracked cog or something.

[sushiboy]

Thanks for the suggestions.

I've greased everything for the sake of it, and checked crank arms, pedals, shoes.

I've checked the cassette and no cracks, and it certainly does not appear to be a derailleur alignment issue.

I'm stumped. Noise is still there in the one middle gear. Could it be a stretched chain?

[DaveM]

Could be the chain though I can't think why it would only happen in one cog. Is the lockring good and tight?

It could be the freehub as well. But when those make noise, it typically shows up first in the outmost cog as that put the most lateral stress on it.

Check your chainring bolts up front for good measure. But unless someone else has a good suggestion, you may have to start trying to swap out parts to see what takes care of it. Chain and cassette are the first places to start since these are "wearing" parts anyway.

[cyclerUK]

No Idea but:-
Check for stiff link/s on the chain. - turn pedals backwards and watch the rear dérailleur. If it jumps then suspect chain.
Check that the top jockey wheel is clear of the sprocket.- adjust "B" screw.
Bent tooth/teeth on that sprocket.