Ok, so I'm planning to build up a new dirt jumper/urban bike sometime soon (tax refund time). Right now I'm not quite sure on a frame, but the Transition Trail or Park looks pretty bombin'. For the time being I'm going to transfer over most of the parts off my STP.

I'm kinda curious about BMX cranks and BBs. Having never ridden or wrenched on BMX bikes in the past, they are completely new to me. It seems that some manufacturers are including them stock on DJ bikes. I see alot of BMX cranks are 4130, so I'd assume they're stronger, but what about the BB. From what I can tell, you have to put a spacer in the BB shell to insure proper bearing preload. What if the shell isn't exactly 68 or 73mm wide though (ie. 67.6mm)? Would the bearings be improperly preloaded?

Does anyone here run a BMX setup on their mountain bike? How's it working out for ya?
Thanks.

nobody huh?

Oh . . . just saw this. FSA's X-Drive and the nearly-identical On One BMX-splined BB come with a ton of spacers/shims (in addition to the main long center spacer) to get everything dialed. When I find the right link, I'll edit my post.

EDIT - The FSA installation instructions are on a text-only page
https://www.fullspeedahead.com/downlo...stallation.pdf

If you end up getting one of these and want an install guide with picts, PM me and I'll dig up the On One PDF. It was a much clearer guide.

you can get euro bb for 19mm or 22mm spindles. you would have to check on the spacer situation and you might have cut one or use a pipe. you would want to be as precise as possible so that the inner bearing race is supported. i guess nearly any bmx crank could work. look at bb, cranks, etc at www.danscomp.com too

this place seems to have some cool cranks:
https://www.gussetbikes.com/gusset/viewcat_mtb.php?i=BBs'n'Cranks



from danscomp:








etc...