I want to replace the ofmega bottom bracket on my Bianchi with a shimano un54 and I am not sure what length is needed. The ofmega spindle is 121mm i think (double crank) but it has a longer and narrower taper than the jis shimano. I want to use a normal double crank. What do I need to measure or look up?
Rans Enduro Sport, Hase Kettweisel Tandem, Merin Bear Valley beater bike
Originally Posted by mazdaspeed
Could I just measure the spindle from a jis bb that used a similar crank and was on a frame with a bb housing that is the same width or close to it?
Different square taper cranks have differrent offsets and, consequently require different BB spindle lengths. What I've done in the past is to test fit the crank on any BB that I happen to have on hand. Then I can make a judgement about whether I need a slightly longer or shorter BB spindle.