Bicycle Mechanics - cassette wobble

After putting on a new chain, I was adjusting the rear derailleur and noticed when the rear wheel was turning but the cassette stationary, there is a definite movement in the cassette.

Can anyone tell me what could cause this, and is it something to be worried about? There isn't much movement, and I probably wouldn't have noticed if I wasn't looking closely at it while making the adjustment. I was having trouble getting the downshifting done correctly. It would go directly from 7th to 9th. I wonder if this is connected to the "wobble".

This is on a 105 nine speed.

Thanks.

Sounds like you have a bent axle in the hub.

Freewheel hub? Change the freewheel it should fix it. It usually does with mine. But I destroy freewheels haha :)

The wobble normally doesn't affect shifting tooo much as I can ride with the wobble for quite a while. However it can definately cause issues in theory I just have never had it happen with me.

Originally posted by Maelstrom
Freewheel hub?

Yup, that would be my guess also.

It is not unusual for them to wiggle a bit, but if you want to make sure do this:
Pull the cassette off of the freehub. If the lock ring was loose that may have been the problem. Check the freehub. Does it have a lot of play? It may wiggle just a little, thats OK. If it loose either the freehub is blown or the retaining bolt is loose. Either way you would have to remove the axle to get at the retaining bolt. It is a hollow bolt and hard to see. Stick a 10mm Allen wrench in there and check to see if it is tight (clockwise) Otherwise just take it off and install a new one.

Thanks, guys!