Bicycle Mechanics - The whole casette wobbles in and out when I spin it. Changing gears is tough.

When I spin my freewheel by hand, the whole gear cluster wobbles in and out. It's not loose and there's no play, but all 7 cogs move together in and out as a unit, making gear shifting difficult in practice.

The rear hub is in good shape, in fact. just rebuilt.

Is the issue with the freehub body or with the actual gear cluster? It's one of the Shimano 7-speed cassettes where you can't remove individual cogs except for the outermost cog.

Any ideas?

If the entire cassett is moving as a unit, it's highly likely the freehub body isn't seated properly or is damaged. What make hub is it?

It's a Shimano 'Parallax' hub.

I can try removing it, and re-seating it. It's got a spacer underneath the cassette.

All freewheels and cassettes wobble to a degree, and that normal amount of wobble doesn't affect shifting.

The wobble happens because the inner part of the freehub body isn't perfectly aligned with the rotating axis of the hub it's attached to. So when the hub spins the freewheel (or cassette) oscillates (wobbles).

If the wobble is more than 1mm or so at the largest sprocket, than it's possible that the freehub body is coming loose from the hub shell, especially if it's worse now than it used to be. (if you never noticed the wobble, you don't have a base line for comparison).

If in doubt bring the wheel only into the local shop ad ask the mechanic to confirm if the wobble is within normal range. Once you've answered that question, you'll be better equipped to solve the shifting question.

It's a Shimano 'Parallax' hub.

I can try removing it, and re-seating it. It's got a spacer underneath the cassette.
There should also be a washer/spacer under the freehub body. Any chance you left it out? Also did you tighten the 10 mm hollow bolt that holds the freehub body to the hub shell adequately?

This looks way more than 1 mm. Everything is tight incl the 10 mm hollow bolt.

I'll try dismantling it and see if anything is funny.

This looks way more than 1 mm. Everything is tight incl the 10 mm hollow bolt.

I'll try dismantling it and see if anything is funny.

It isn't rare that when reattaching the freehub body, folks don't seat it right, or even shave a bit of the hub side of the spline, causing more misalignment. Pull it apart, and check the hub spline for distortion or shaving, then assemble it doing your utmost to seat it straight.

SUCCESS!!

I dismantled it and reassembled and voila: No wobble!

If you, or someone else, recently removed and dis-assembled the cassette, I'd guess that they (or you) left a spacer out of the re-assembled unit. Remove the cassette from the hub, check the spacing between each cog, and see if you can find an excessive space between any two cogs.