Bicycle Tutor

Hi there,
I have recently purchased a old bike that has Mavic Aksuim wheels.
My problem is that the cassette is loose, even when I tighten it as much as possible. I have removed it and checked the hub it seems fine (nice n tight). One thing I did notice is that the smallest ring wont go completely over the splines... I am guessing this would be a problem... as it won't compress the rest of the cassette. Can i put a an extra spacer in some where to tighten it up or have I got the wrong cassette for the hub?
I believe the cassette I have is a shimano 9 speed, any ideas?
Regards,

It sounds like your cassette is missing a spacer between the smallest sprocket and the rest of the cassette. Check with your local bike shop, they'll probably have an extra one lying around.

Actually, the smallest cog should hang over the edge of the freehub body by just a tiny amount. That way the lock ring tightens down on it and secures the whole cassette.
If your shifting is all working fine, the spacing between the cogs should be fine. It could be that there is a missing spacer at the back of the cassette (behind the largest cog). But it may be hard to check your shifting if the cassette is flopping around.

Thanks guys,
I had another look at it last night, and it would seem that the problem is either a plastic spacer being two thin (there are two fitted in) or the 12 tooth cog is not compatible with this cassette (off another cassette).
I managed to get another 12 tooth cog and could immediately see the difference in thickness as this one allowed me to tighten up the cassette properly. But unfortunately for me that spare cog is missing teeth.
My question is this, is it possible to get plastic spacers in different mm? or is it possible to purchase individual 12 tooth cogs to fit on my cassette?
thanks for the help.
rgds,

You can get either spacers or individual cogs. JensonUSA looks to have a good selection as do several online sources. Local bikes shops often have spacers and may have a cog around though that is less likely.

On the spacer, I'd check where the outer cog goes up against the 2nd cog. Sometimes there are little bolt heads there that require a small cutout in the spacer for everything to fit flush. A non-specific replacement spacer may or may not have these.