Wobbly chainring

Chris S

Guru
Location
Sparkhill
The top of my chainring moves laterally by up to 5mm during a single rotation. Is this usual on a 1990 Raleigh Chiltern?

If I tighten up the bottom bracket to reduce the movement then it binds in some places.
(I'm currently waiting for a crank puller to remove it and inspect it properly)
 

mrandmrspoves

Middle aged bald git.
Location
Narfuk
Rotate chainset until cranks are vertical and then hold the crank arms near the padals and try rocking them towards and away from you. If there is lateral movement it is a bottom bracket issue. If no lateral movement, check chainring bolts. If chainring bolts are tight and there's no lateral play in the bottom bracket, the chainring is warped slightly. You can gently straighten it with a large adjustable spanner.
 

Cycleops

Legendary Member
Location
Accra, Ghana
Sounds like the BB is badly worn allowing vertical and probably horizontal movement which you should be able to feel by holding the cranks.

Are the cranks cottered?
 
OP
Chris S

Chris S

Guru
Location
Sparkhill
No - they're square tapered cranks and there aren't any chain ring bolts (it's a cheap one piece unit).

It's definitely a bottom bracket issue and I don't think a 5mm wobble is acceptable, it could damage the chain. I'll have to wait until the crank puller arrives and then look at this properly.
 

Sharky

Guru
Location
Kent
Not sure that it is a BB problem. If out by5mm on the chain ring, then it would be even more noticeable with the pedals and you would feel it when you ride.
 
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12boy

Veteran
Location
Casper WY USA
Lets hope a 25 buck Shimano BB will make you well. Frequently one piece crank/chain ring setups aren't the stoutest and it's possible the tapered areas inside the crank arm are worn or deformed. If you have some other crank/ chain ring parts you can see if the problem persists with them, once you get your puller.
 
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