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Whilst riding home tonight I managed to get thrown off my bike twice, thanks to sudden chainslip.
The cassette, chain and cranks are barely a month old and haven't covered more than 150 miles, plus the chain slip occurred in both the large and middle chainrings, so I don't think it's the cranks. It seems to happen in one specific cog though.
What's the prognosis, is it (another) new chain and cassette?
Freehub slipping?
Don't think so, it happened on a specific cog at the back. Will try a different wheelset just in case though.
Have you fitted the specific cog arse-about-face?
What type/make is the cassette, chain etc
Bent tooth or stiff link would be the next things I checked.
You say new cranks ,are the rings new as well?
Had it once with a brand new complete drivetrain, which had an unbranded cassette. A swap to a Shimano cassette solved this problem, but you may have something totally different happening.
If it's a specific cog at the back, I'd second the suggestion already made, that the cog in question has been fitted the wrong way round.
Banana skin stuck in that cog?
chain length ok?
Chain fitted correct way round if 10 speed?
It's all XT, from the crankset (with new rings) to the cassette. Yes, I did check whether the errant cog was fitted the wrong way around, but it appears not to be.
I'll try shortening the chain and adjusting the mech clearance to see if that helps.
XT 10 speed chains are directional - is it the right way round?
How do your pulley wheels look?
Is the mech/hanger straight?
EDIT - which cog does it jump in?
It's nine speed, so there's no chain alignment and it slips on the 14T cog. The mech hanger is straight - it's a brand new frame too and the jockey wheels look good, I may well replace them though as a precaution.
It's bizarre isn't it?
Cassette lockring done up to proper torque, or has it come undone and cogs are now loose? Usually needs about 30 to 40 Nm, but will say on the lockring. Basically needs to be done up quite tight.
14t I guess is the second or third smallest so at the top of the stack. I've had issues with an incompatibility with a certain cassette with a freehub where the top cogs don't even slot onto the freehub splines and just rotate round until the lockring is fully tight.
Also, is it slipping on the cog or is it jumping or trying to jump off or onto it? Can seem like it's slipping. If the latter it's likely an indexing issue.
It's slipping on the cog - I've reset the indexing twice and the problem won't go away, the hub itself is a Hope Pro 2, which has started making some noise, so I assume the freehub bearings could be ronnied in which case I've my suspect. I'm going to do a wheel swap today with another set of Pro2 wheels and that'll hopefully give me my answer.
Adam is on the money here I think, bent hanger, had it on a road bike a couple of weeks ago, just one cog it slipped in, hanger was out a few mm.
It was the freehub bearings.
Have put the same cassette onto another ProII wheelset and have taken the bike out for a spin, no slippage at all this time.
I've checked the old wheel and the freehub bearing are definitely on their way out.