I've had this mountain bike a little over 2 yrs. I had it serviced when I bought it because it was recommended even though it's not an expensive bike. One day the chain slipped off multiple times which had never happened. Once I flipped it over I noticed the cassette was wobbly. Would this be an expensive repair and what exactly should I be looking at to have replaced?

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    based in the description, the best advice you can hope for is "take it back to the shop and have them look at it" – Paul H Jun 20 '19 at 22:23
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    You need to tighten either the lockring or freehub. If you can find a bike coop in your area, they will give you access to tools and expertise. This isn't an expensive repair and most mechanics (at non-peak hours) will let you watch and explain what they are doing. – Daniel Portin Jun 20 '19 at 22:55
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    See if there isn't a "bike coop" in your town. – Daniel R Hicks Jun 21 '19 at 0:37
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    I suspect there's more than one thing going on here. Please check if the rim moves side-to-side, to see if there's play in the bearings or if you have a broken axle. – Criggie Jun 21 '19 at 9:47
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    Was the bike used when you got it? Do you know what the mileage on the chain/cassette is ? The chain slip may be caused by wear, which is different to the cassette's wobble. – Criggie Jun 21 '19 at 9:47

Could be a number of things:

Cassette is loose on the freehub body. If the cassette lockring has come loose the cassette sprockets can slide axially on the freehub body and possible 'rock' on it a little. If you take the wheel out of the frame you should be able to see of the lockring is loose quite easily. To tighten it you need a chainwhip, lockring tool and a big wrench. It would not cost much to have local bike repair shop do this.

Freehub body is loose on the hub: If it looks like the cassette is firmly on the freehub body, but is moving relative to the rest of the hub, the body may be loose, or one of the bearings supporting it is damaged. To tighten the freehub you'd need to get the cassette off, and then figure out how your particular freehub is secured. Again, your local bie repair shop can do this for you.

Possibly the axle or hub bearings are broken. With the wheel in the bike try pushing and pulling laterally on the wheel rim. If there damage to the bearings there will be movement.

If the freehub or hub bearings are damaged on an inexpensive bike the best thing to do is just get a whole new wheel. Inexpensive wheels are not worth rebuilding to replace the hub as the cost of rebuilding will be a significant fraction of the cost of a new wheel.

  • Thanks for ALL the feedback... will try ALL the suggestions asap and hopefully be able to get back to riding sooner than later. Thanks again. – Just for kicks Jun 22 '19 at 1:27
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    Minor point- to tighten a cassette lock ring you don’t need a chain whip. That’s only for loosening it. And the wrench doesn’t need to be particularly large. Any medium sized adjustable wrench should be fine – Andrew Aug 15 '19 at 11:05

If it is a cheap screw on cassette, and the play is in the cassette itself, just replace it. A lot of the cheap ones get play in them after a while. Cheers

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    How can a beginner work out if they have a cheap screw on cassette? – David Richerby Jul 16 '19 at 21:59
  • I guess by looking at it, and seeing if it has an external lock-ring, Is the easiest way – Graeme Dumbrell Jul 18 '19 at 7:41
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    what you are talking about is called a freewheel. – Tooniis Aug 15 '19 at 12:07

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