Periodically I’ve felt a slight ‘kick’ from my drivetrain when pedalling but haven’t really paid it much attention (it feels a bit like a stiff chain link).
Today I got caught out in heavy rain for sometime so presumably lost most of my lube; the ‘kick’ (felt through the pedals) was much more noticeable.
If only occurs when I’m using the 4th smallest cog (third up from the smallest) in any chainring (I’m still 3×9) and no other.
I can find no movement from the cog and the whole cassette seems fine (there’s also no scoring on my famously soft aluminium Hope freehub which I would have expected if there was any movement at all). I’ve removed and retighten the cassette and can see no worn or broken teeth on the cog.
The cassette (SRAM 980) and chain (KMC) are reasonable new and were fitted together.
The 980 cassette comes in 4 pieces (excluding the lock ring) with the 1st and 2nd cogs separate, a block of 4 cogs and a block of 3. The problem cog is the second on the block of 4 and can’t move independently of other cogs on the block.
There’s no clearance issues of contact between the cassette, chain and rear mech and I can find no reason for the issue so I was wondering if anyone had any ideas?
I suppose that a new cassette might solve it but there doesn’t seem to be any wear on the one I have.