Mountain Bike Reviews Forum banner
1 - 8 of 8 Posts

·
Registered
Joined
·
13 Posts
Discussion Starter · #1 ·
I was helping to clean my sons MTB the other night and we had the bike upside down to clean the crank, chain etc. I noticed that after spinning the wheel with the crank, the rear cassette is "floating" around while the wheel freewheels. When I say "floating" I mean its moving around, almost in an up and down motion back there, so much that it pulls the chain and ever so slightly rocks the pedals back and forth while the are still ....

What can be causing this? I don't think its normal so I'm figuring something is bent back there?

Bike is an 03 Trek MT220 ... It has a Shimano drivetrain .. 21 speed, Mega Range cassette out back.

Any suggestions before I take it in to the LBS would be great ..... Thanks! :thumbsup:
 

·
Registered
Joined
·
811 Posts
Meaning it has movement from side to side? Is the thing loose?

I'd take the wheel off and using a lockring tightener/remover, I'd tighten it down and see if that's the issue.
 

·
Premium Member
Joined
·
48,238 Posts
Jet300 said:
I was helping to clean my sons MTB the other night and we had the bike upside down to clean the crank, chain etc. I noticed that after spinning the wheel with the crank, the rear cassette is "floating" around while the wheel freewheels. When I say "floating" I mean its moving around, almost in an up and down motion back there, so much that it pulls the chain and ever so slightly rocks the pedals back and forth while the are still ....

What can be causing this? I don't think its normal so I'm figuring something is bent back there?

Bike is an 03 Trek MT220 ... It has a Shimano drivetrain .. 21 speed, Mega Range cassette out back.

Any suggestions before I take it in to the LBS would be great ..... Thanks! :thumbsup:
Do check that the lockring is tight, but cassette wobble is not unusual and not a problem in most cases.

It is caused by the hub not being perfectly concentric.
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #4 ·
Nope not side to side. If you look at the cluster dead on from the right side of the bike and spin the wheel, its moving about its axis in an almost elliptical motion ... Meaning it moves up and down with relation to the ground .....

Basically the wheel is spinning, the drive train is at a dead stop, but the rear cluster is dancing around in an elliptical motion about its axis. There is no lateral motion at all.

I'm going to remove the rear wheel when I go home and look for the obvious.
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #5 ·
shiggy said:
Do check that the lockring is tight, but cassette wobble is not unusual and not a problem in most cases.

It is caused by the hub not being perfectly concentric.

WOBBLE
That was the word I was searching for! Thanks! :thumbsup:

Yes it is wobbling all over the place .... Hub not concentric? :eek: I thought it would be more precise a component than that .. LOL

I will definitely check the lock ring tonight ., Thanks ....
 

·
Registered
Joined
·
1,498 Posts
Cassette wobble is normal within bounds. it isn't that the hub isn't concentric, but that the attachment of the inner part of the freehub body isn't perfectly concentric to the hub shell (none are). So when the hub spins the freehub's axis wobbles a bit, as a bent pedal does, and you see the result as cassette movement.

If it's within normal bounds, namely a millimeter or two, and doesn't affect function all is well and you can forget you ever noticed. If it's more pronounced, and/or the freehub or cassette are loose with respect to the hub shell, it could be that that interface is loose and needs to be attended to before riding makes it worse to the point of being unrepairable.
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #7 ·
Wow, cool thanks for all the quick replies :thumbsup: What a great forum I found, I appreciate the help ... Its real dirty back there, so this gives me an good excuse to take it apart make sure its ok and give it a real good cleaning ...

Shiggy: Using "wobble" helped me further search the topic .. Apparently like you guys said its pretty normal .. I found this Youtube vid showing exactly what my sons bike is doing ...

 
1 - 8 of 8 Posts
Top