Wobbly crankset

[grellboy]

Evening. Noticed that my chain rings were rubbing against the chain recently and the crank had a noticeable wobble. I removed the crank and had a look inside the frame. There was no grease left on the crank arm thing (the horizontal cylinder part that goes through the frame) so I had to bang it with a hammer to remove it. Once removed I checked the bb (bb30 - so just a couple of bearing rings really) and these seemed fine, so once I cleaned and regreased everything I slid the crank back through the bike and reattached it but wobble remains. Any ideas? Nothing seemed obviously damaged.

 

[Cycleops]

You need new bearings by the sound of it. Press fit, so you'll need some tools.
Edit: Do you mean the wobble is when you move cranks or the chainring is wobbly (not running true) ?

 

[Twilkes]

Do both sides of the crank wobble in the same way at the same time, or just the drive side? What crankset is it?

 

[sleuthey]

It sounds like either your BB Spindle is bent or your chain wheel is warped.

 

[Dogtrousers]

I sounds like your BB is shot. Time for a new one.

At least - that's from my experience. I had a wobble in the crank and the bearings felt grindy, so I replaced the BB (actually I got the LBS to do it) and problem solved. But there are so many different kinds of BB in the world that my experience may not apply.

 

[Twilkes]

I sounds like your BB is shot. Time for a new one.

At least - that's from my experience. I had a wobble in the crank and the bearings felt grindy, so I replaced the BB (actually I got the LBS to do it) and problem solved. But there are so many different kinds of BB in the world that my experience may not apply.

It's worth making sure exactly what the problem is first though - I took a wobbly crank into a bike shop and they changed the BB, only for the problem to remain. Turns out the part of the spindle that was supposed to be machined fast into the crank was coming loose, so the whole crank had to be tossed. BB was fine and i kept the old one as a spare.

Does depend on whether something is wobbling while stationary i.e. it's loose, or whether OP means that the chainline is moving side to side while they pedal.

 

[grellboy]

Thanks

It's worth making sure exactly what the problem is first though - I took a wobbly crank into a bike shop and they changed the BB, only for the problem to remain. Turns out the part of the spindle that was supposed to be machined fast into the crank was coming loose, so the whole crank had to be tossed. BB was fine and i kept the old one as a spare.

Does depend on whether something is wobbling while stationary i.e. it's loose, or whether OP means that the chainline is moving side to side while they pedal.

Thanks for your replies everyone. It's an Fsa Omega crank and it wobbles both when still and when turning.

 

[Twilkes]

Thanks


Thanks for your replies everyone. It's an Fsa Omega crank and it wobbles both when still and when turning.

Mine was an FSA crank, whatever the cheap stock one supplied with Cannondale Optimo bikes was. If only the driveside wobbles, and there's no corresponding wobble on the non-drive side, then it may be the same problem I had, the spindle coming loose from the crank. You could take it back out to check. If that's what it is then your crankset is gubbed. Would be replaced under warranty, or just have to buy a new one.

Good news is that I have a very lightly used Cannondale 50-34 170mm BB30 crankset for sale if you need it.

 

[Cycleops]

Thanks


Thanks for your replies everyone. It's an Fsa Omega crank and it wobbles both when still and when turning.

But where does it wobble, that is the question? Is it nobler to buy a new chainring or to suffer the slings and arrows of changing the hated push fit bearings?
Sorry my Shakespeare is a bit off but you get the Idea.