Singlespeed & Fixed Gear"I still feel that variable gears are only for people over forty-five.
Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)
I don't think you need a new bb. The taper on the cranks are the same. The spindle length might throw your chainline off a little, though you can redish your wheel or use some spacers.
