I think the wobble here is caused by imperfections in the interface between the crank and the square taper spindle, as explained by RJ the Bike Guy in this video: https://youtu.be/-mU6Dyt4SQg?si=ZdLK8rKZAcy6_HKD
However, I’ve rotated the cranks between all 4 positions on the spindle and this seems to be about the best one. Is this a normal/acceptable amount of wobble?
How much crank and chainring wobble is ok?
byu/allismg inbikewrench
by allismg
4 Comments
Wobble in the crank will means the bearings in the bottom bracket will grind and fatigue faster, the chain-rings wobble will cause your chain to fall off the front and wear the rear cassette prematurely.
You want it straight as possible without compromise, no amount of wobble is advisable. It will be more prone to coming off and wear and rubbing cross chaining in certain gears with a triple front.
I think the main issue with chainring wobble is how it impacts front shifting. When the chainrings travel, you are trying to shift to a moving destination. So no single shifted position is ideal for the chainring, because it’s always in a different spot. If you can’t shift consistently in the front, then it’s time to do some replacing.
I’ve advised a lot of repairs on 80s and 90s bikes, and this looks completely normal.
This is nothing to worry about.
Your crank/spider is wobbling, I think you have a bent BB spindle or mis installed crank arm (unlikely)