Bent / Wobbly chainring

[Jp1970]

Hi

Just noticed that my outer chain ring (FSA vero Compact) is either slightly bent or wobbly. I decided to inspect it after the chain unshipped whilst changing up going down a short hill on a club run. Luckily I wasn't applying a great deal of force/power when chain came off.

I've taken off the chainrings and crankset (drive side only) and 'checked" if the outer chainring is warped / bent by placing the ring flat on the kitchen worktop to try and detect wobble..!!
Having re assembled the crankset back on it still has a very small wobble... About 1-2mm when checking against the FD.

is it time for a new chainring or crankset or BB? Or do I need to get the hammer out !!..

Thanks in advance ...

[profpointy]

I had similar symptoms and it turned out the (solid,square taper) axle was bent. With that design at least, you could roll the (bb) axle on a table and see summat was amiss. Frankly I was suprised a lesser athlete like me could bent a solid steel bar but hey ho. Your problem may or may not be same thing.

[531colin]

Firstly, check there is no play in the bearings.
If the bearings have no play, you need to dismantle it and re-assemble it 180 degrees different to where it is now....if its square taper, just assemble it with both cranks parallel, and see if the wobble is the same or different.
reason....there are always manufacturing tolerances. a good mechanic will always assemble something so the tolerances cancel out, rather than add up.
Or....rotate the chainring on the spider
If you can't get it to run true, its OK to bend the chainring a bit.....Sheldon on the subject.....http://www.sheldonbrown.com/straighten-chw.html

[rmurphy195]

Do the other chainrings wobble? - just a thought, if one does and the others do as well, maybe this points to the BB or crank, but if only one chainring wobbles, then maybe you've isolated the problem.

[[XAP]Bob]

I presume it's not as bad as my recent post - but a bent spider could pull a wobble into a ring which would otherwise remain straight...

[Brian73]

The profiled teeth on most modern rings can give the impression of a wobble.

I had a bent middle ring on an alloy triple, I used a big screwdriver wedged between the inner and middle to lever it straight very gently.

[andrewjoseph]

i had a wobble on my big ring, a very thin washer between it and the spider sorted it.