My chain keeps slipping/when I go onto my 11 tooth rear cog. Any ideas?

Kit as follows:
Ultegra chainset 39/53 I think, Ultegra 11-23 cassette. Mavic Askium wheels, Connex 10spd chain.DA rear mech

What I've tried:
chain too long - yes it was, now correct length but still slipping/skipping (moral - don't fettle when small people are nagging you).
Stiff chain link(s) - checked and double checked. Tis a new chain, flexed it to ensure no tight links.
Cream crackered rear mech: swapped to the spare Ultegra I had, made no difference. DA rear mech now awaiting strip,clean and grease.

cable snagging - my cable adjusters have both broken, possibly causing some cable stick? To be replaced as soon as the postie delivers them.

Cassette play/wear? My cassette has some play on the freewheel. I am using the Mavic spacer but there still is a bit of play with the cogs furthest away from the lockring. Lockring is as tight as i can get it. I know this may sound strange but is it possible to fit a shimano cassette to a mavic campag freehub?  39

Worn cassette teeth - no bent teeth, cassette is probably nearing the end of its life  7

Anyway at a loss. Any thoughts appreciated. The slipping/skipping is hard to replicate when on the workstand, only when actually pedalling.
Ta in advance


cat1commuter [1422 posts] 7 years ago

Skipping is usually caused by using a new chain on a worn cassette in my experience, though this is more likely to happen first on the sprockets which you use the most.

Your cassette definitely shouldn't have play on the freewheel! Campagnolo compatible freehubs are wider than Shimano and have a different spline pattern. I'm not sure what the Mavic spacer does. The only spacers I have come across are for running 7 speed cassettes on 8/9/10 speed Shimano compatible freehubs.

You can get conversion kits for some wheels to switch between Campagnolo and Shimano.

Marchisio make cassettes so that you can run Shimano 10 speed on Campagnolo freehubs.

dave atkinson [6292 posts] 7 years ago

sounds to me like you've worn out your little cog. it's often the first to go because the load is spread over the least number of teeth, which increases the load on each tooth and consequently the wear. If you use it a lot anyway (some people do, some don't) it's almost certainly that. Cat1's right, play in your cassette is definitely a bad thing. 10spd cassettes come with a spacer, depending on your lockring it's possible you'll need another one though it's unusual.

radar [48 posts] 7 years ago

Thanks for those replies... I sort of guessed as much. New cassette will have to wait till next month. Just bought some new forks (developed a very worrying creak - carbon steerer sort of worries me).

Mavic freewheels have a spacer that fits on the freehub before the cassette (in the case of shimano).

When I bought the wheels I didn't notice any play at all. They were definitely shimano freehub mavics. Back wheel exploded after 4 months and I was sent a replacement. Only just noticed this play in the last week or so. Connected with my chain skipping thought process it was just a possibility that needed eliminating. Pretty positive it is a shimano compat. freehub. The diameter of the freehub is about 1 mm (or less) smaller than the diameter of the splines on my ultegra cassette (and the mavic spacer). Maybe with all the rain we had earlier this year the freehub has shrunk!