SO I have an xc race tomorrow morning, on a ride last week I snapped a rear mech hanger which catapulted the mech and chain into the rear wheel trashing the lot.

I have only just got around to rebuilding it after ordering new hanger, mech and chain. It shifts up and down fine but when putting power down in the smaller sprockets the chain seems to skip forwards over the teeth making.

I cannot think my cassette is over worn as it is only about 100 miles old, is there anything I could be missing or any way to bodge it so I can race tomorrow?

might you have bent the frame as well as the hanger ?
(and are you sure it isn’t cracked somewhere?)

have you missed any spacers behing the cassette to keep it from moving around ?

Is the wheel new or might your hub have a bent/broken axle ?

Just checked frame, wheel is old but was checked and rebuilt by LBS, I think i am going to have to make a dash to LBS and hope new cassette does the trick.

I guess you may have worn the small cogs if you ride in them a lot.

You can re use your old chain by straightening the twisted link.

SP is guessing BTW, I can’t see any of his ideas being relevant.

Have you cleaned off the grease that comes on the chain when new. sounds daft but that can make it skip sometimes. Clean off thoroughly and then relube with normal chain lube.

GUESSING, al ? – I’ll have you know that I’ve carefully examined the bike in question and those are my considered opinions. If I’d been guessing I’d have put question marks in my post

I assume that’s a hilarious joke.

Your 1st post is a classic in “don’t believe everything(anything?) you see on the net”.

Yeah – I stopped short of suggesting that several of the OPs cogs might be worn after 100 miles though

b limitor screw ?

1 1/2 hrs round trip to evans later, and another hrs worth of swearing and I am still no further on, which at least points to mechanical ineptitude on my part somewhere which should be fixable. Will try the de-grease and re-lube suggestion next thanks!!

Oh and checked B limit screw its about the top jockey wheel sits about 6mm below the largest sprocket

Stating the obvious, but, you did check the length of the chain?

Yeh measured chain length against old chain taking a bit of stretch into account.

Is there a stiff chain link? The tighter angle on the small cogs sometimes means the chain disengages and slips.