Ultegra/FSA Crank & BB Compatibility

[pgrizzwald]

I'm currently running an FSA SL-K carbon crankset with an FSA BB-6000 MegaExo bottom bracket. But, I'm looking at possibly switching to an Ultegra 6800 crankset. Is it possible to run the Ultegra 6800 crank with this FSA bottom bracket? I've heard you can run FSA cranks with Shimano BBs, but does this go both ways since they are both 24mm spindles? Would appreciate your thoughts & experiences with this!

[Bostic]

The FSA Carbon crank is ever so slightly wider on one side so their bottom bracket works and standard Shimano doesn't. This is not the case with the FSA alloy cranks. Guess how I found out. There might be some play when you change to the Shimano.

[pgrizzwald]

The FSA Carbon crank is ever so slightly wider on one side so their bottom bracket works and standard Shimano doesn't. This is not the case with the FSA alloy cranks. Guess how I found out. There might be some play when you change to the Shimano.

Wider as in the spindle is a little longer? If that's the case, couldn't that just be solved with some combo of washers/spacers?

[Bostic]

From a helpful poster on Weightweenies

FSA Energy/Gossamer cranks have ~25mm OD spindles which are compatible with Shimano Hollowtech spec'd bottom brackets (25mmx37mmx7mm) and don't incorporate crush washer or wave spring washers for proper pre-load. The FSA's 'Light' variants (K-Force Light/SL-K Light) incorporate the wave spring washer for proper pre-load and spacing so have narrower 6mm bearings but these cranks also have a slightly larger spindle diameter (~25.5mm) which makes for an overly tight fit which will most likely result in damage of the bearings if a Shimano compatible bottom bracket is used - been there, done that with lots of $$$ attached!

[cmbicycles]

Shimano and FSA are both 24mm spindle (as is GXP except it steps down at the NDS arm to 22mm). Sometimes it works to use one (FSA/Shim) with the other, sometimes it doesn't. I'd say if you are ordering the crank, it makes more sense to get a bb with it, or take your chances and try it out.

FWIW, from FSA's website:
FSA’s 24mm spindle crank & bottom bracket system: MegaExo cranks are available for road and mountain applications and compatible with 68, 73, and 83mm English thread, 70mm Italian thread, and several press-fit bottom bracket standards. MegaExo bottom brackets are available in all thread standards and offer compatibility with Shimano cranks.

[pgrizzwald]

Thanks guys. Seems a bit hit or miss. I guess I could just try it, and if it won't fit, an Ultegra BB is like $15. Does anyone else have any real world experiences running this combo?