Cassette wobble

Hey,

I noticed a bit of a clunk when coming back on to the pedals after coasting the other day. This is a bike I haven't ridden much since I built it, but I don't remember it from when I fitted the cassette. I've taken it all apart and nothing looks damaged, and all parts are present.

Gripping the cassette, I can wobble it. There's only a very slight wobble on the free hub when the cassette is removed, and no discernible play if I wobble the wheel while in the frame.

Cassette is a CS-M8000 11 speed Deore XT, on a FH-M8010 rear hub. Both mountain bike parts, so no spacer required like it would with a road hub, but it feels like I need another spacer in there.

Anything else I should check? Or, if I go down the additional spacer route, what do I need?

Thanks.

https://youtu.be/vN4FzrE5P8I

Double check that your smallest cog is seated properly, then tighten it back up to spec.

Ed.: hadn’t clocked that you’ve dis and reassembled it.

Definitely loose cassette rather than a freewheel issue- the cogs shouldn’t have that amount of independent play (assuming 1-3 are a single unit, which it looks like).

I’ve had that issue when, in haste, I’ve mis-installed the smallest cog. The lockring then tightens correctly, but the cogs aren’t compressing, leading to this. If it turns out you do need spacers, I might have a couple suitable .5mm freehub spacers you can have in SE24.

I'll take it apart again when i get home today and double check that. The cassette has 1-2-3 and 4-5-6 in two groups, the singles for the rest. All the midway spacers are present and correct.

I did manage to get a 1mm spacer from my LBS at lunch time today, so if checking the smallest cog doesn't prove to be the issue, I'll try rebuilding it with that spacer and see where that gets me.

Have had similar on a 12 speed cassette, and it was what Eseman said. The smallest sprocket barely engages with the splines on the free hub so it's really easy to knock it out of place as you tighten the lock ring.

Thanks both. I finally managed to get out to the garage. The smallest sprocket is definitely sitting properly, but it still took adding a slim spacer behind the cassette to remove that play that allowed the cassette to split.

With it all back together, both on the bench and with the wheel in the frame, I now see a bit of play which I think is coming from the free hub body, as the cassette is now moving as one. Does that look right? Tricky to video as everything seems to move, but hopefully it is visible.

https://youtu.be/KEs1p60Bqao

https://www.bikeforums.net/bicycle-mechanics/538058-wobbly-freehub.html

Mountain Bike Performance Handbook by Lennard Zinn:

"5.2C: Tightening up a Wobbly Freehub.

Many freehubs wobble as they spin. You can see it when the bike is free-wheeling. Grab your freehub and rock it to see how much play yours has. Eliminating the wobble will improve shifting and reduce freehub wear and friction.

You can practically eliminate the wobble in a Shimano freehub by removing one internal shim. The shims are inside to account for possible deviations in manufacturing tolerances. Since it is better to have a wobbly freehub than one that is too tight to turn, the shims are automatically installed in all freehubs to add a little play. Remove the thinnest shim, and reassemble the freehub, tightening the hub bearing race down fully with the tool. The freehub should spin freely without rocking. The cogs will now stay in line and shift faster.

If removing the shim tightens the freehub too much, yet there is play in it with the shim installed (or if there is still play after removing the shim), you can eliminate the play with some sanding. Sand the bottom of the hub-bearing race by rubbing it on a piece of sandpaper held down on a flat surface. You are sanding the surface at the end of the threads. Reassemble the freehub with one or both shims installed, whatever works best."

Ctc forum have quite a lot of information on the 'shimming' of shimano freehubs to remove the play. This post includes a diagram of the freehub internals.

https://forum.cyclinguk.org/viewtopic.php?f=5&t=145496

To get into the internals of the freehub to remove a shim you'll need a tool. Search freehub removal tool on eBay.

If you can't remove the play with cassette spacers I'd maybe look at this.

Useful video of the tool in use.

https://m.aliexpress.com/item/1005001484836796.html.

That video cut off just when it was getting satisfying to watch.

Thanks @user74931 that looks good. I tried an oversized spacer behind my cassette, to the point I could only just screw the screw it together, and there was no play around the cassette so what remains must be from the free hub.