What tells you when bottom bracket is shot?

pastryboy

With no chain on, when pedals spun fast:

Bike A: spins freely - no noise whatsoever
Bike B - spins freely but some noise - the cranks, when pushed, have a slight wobble (front to back it I'm looking at the bike side on)

Is the bottom bracket on B on the way out? What happens if I just ride on with it?

nicklouse

There is a fairly simple test to determine if the bottom bracket bearing is worn out. Shift the chain to the inner most rear sprockets front and rear. Drop the chain off the smallest front ring, and arrange it so it will not strike the chainrings. Spin the crank while holding the bike with one hand. If you feel an obvious rumbling or grinding feeling, the bearing are wore out and the unit should be replaced. Very worn bottom brackets will actually make a grinding noise.

http://www.parktool.com/blog/repair-hel ... ervice-bbt

and not much until you cant stand it anymore.

pastryboy

Thanks, pretty conclusive the BB needs replacing then. Not surprised given the age of the bike but, if there's no risk, I'll just leave it as it's only backup and I can't afford any new bits for it.