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Cassette wobble?

Old 08-09-17, 05:06 PM
  #1  
chris1969
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Cassette wobble?

Hi

The rear wheel on my racing bike has a Shimano 8 speed cassette with 25/12 teeth (largest/smallest sprockets). The two outer sprockets are separate from the rest of the cassette which I think is standard on this sort of cassette. The freehub measures about 35/36mm from where it enters the wheel to the end of the ribs which run along its length.

I recently removed the cassette and reinstalled it. When I tightened the lockring I noticed that the outer sprockets had a few millimetres room to move from side to side. I also have a hybrid bike with an 8 speed cassette and so I put that onto the racer where it fitted nice and snugly. I put the two cassettes side by side and the hybrid is about 1-2mm longer from outer to inner sprocket.

So my question is why is there room for the sprockets on the 25/12 cassettes to wobble from side to side. Presumably it can't be a design feature as it would make shifting difficult. I can think of a couple of explanations:

1) The shop fitted the wrong cassette. Possible but my understanding is that a 35mm hub is standard size for an 8 speed.
2) I mislaid a part, perhaps a spacer, when I removed the cassette?

Is there a way I can test these ideas, and are there any other possibilities. I’d be really grateful for thoughts/ideas here. I’m finding it a bit of a headscratcher

Thanks

Chris
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Old 08-09-17, 08:36 PM
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woodcraft
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Sounds like you need a shim behind the cassette.

the smallest cog should be just proud of the threaded end of the freehub

so that the lockring tightens the cassette before it bottoms out.

If it fit well before, maybe the shim got misplaced.
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Old 08-09-17, 08:41 PM
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+1

Your cassette is too short (thin?) for the space on the freehub. So the lockring is bottoming out on the end of the freehub rather than compressing the cassette as it should.

Add enough spacer(s) behind the cassette to push the front out u til it overhangs the freehub by 1mm or so, then the lockring will tighten the cassette properly.
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Old 08-09-17, 08:49 PM
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Originally Posted by chris1969 View Post
2) I mislaid a part, perhaps a spacer, when I removed the cassette?
Yes
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Old 08-09-17, 09:22 PM
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Given that the problem seems to have appeared after you took it apart and reassembled the smart money is that you either forgot a spacer or didn't get things back together correctly. I'm not aware of any cassette where the cogs are loose after lockring tightening.

Whenever I remove a cassette, I loop a long tie wrap through the center so that things stay in sequence and orientation.

- Mark
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Old 08-11-17, 07:43 AM
  #6  
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There is often a 1mm spacer that slides on the freehub PRIOR to the cassette sliding on. Sometimes, this 1mm spacer (looks like a jagged ring) can stick to the back of the largest sprocket, and perhaps get lost during cleaning or other such things. Also, this may not apply to your cassette, but a few of my cassettes (older Interactive Glide ones) use a 1mm spacer just inside the second-to-the-smallest sprocket ("6th gear" on my cassettes). This sprocket is designed to be separate from the rest of the cassette, but it's not as thick as the smallest sprocket, and it needs a 1mm spacer installed just prior to it to keep the sprocket spacing consistent.

As noted, if your cassette is loose or rattles on the hub after tightening the lock ring, a spacer is missing somewhere.
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Old 08-11-17, 04:55 PM
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chris1969
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Cassette wobble and space

Thanks everyone

It seems most likely that I've mislaid the spacer or (possibly) that the LBS didn't fit it in the first place. Interestingly there was a development after my original post. I had ordered another 8 speed cassette for my 'store' which arrived yesterday. I fitted this onto my bike and it was nice and snug without any spacer.

This new cassette was shimano 8 speed and was labelled as a Shimano on both the lock-ring and and one of the sprockets. I went back to the original and it was labelled as Shimano on the lockring but not the cassette. So it looks like the LBS might have spliced together a non-Shimano cassette with a lockring and (possibly) included a spacer which I then lost.

So it looks like problem solved. Thanks very much everyone for the really helpful advice.

Chris
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