Had to pick between a new crank or a bottom bracket last week

I was half way through a tune up on a late 90s Trek mountain bike when I found the crank was wobbling. Pulled it off and the spindle had a groove worn into it from years of riding without grease. The bottom bracket bearings were shot too, but the cups were still good. I had to decide between a whole new square taper crank or just replacing the bottom bracket and hoping the old crank held up. I went with a new Shimano BB for $18 and kept the original crank. It tightened up fine and the wobble is gone, but I know the spindle is still wearing down in there. Has anyone else run a grooved spindle for a while or am I just kicking the can down the road?

2 comments

2 Comments

thomas_roberts6d ago

Replace that crank now" sounds like fear mongering, I've run grooved spindles for years without issues.

richard_shah6d ago

Replace that crank now before it fails on a ride. A worn spindle can suddenly snap under load and leave you walking home with a broken bike. A used square taper crank from a co-op or online is cheap insurance compared to the headache of a roadside repair.