Bicycle Mechanics - External bottom bracket <--> cranks
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I'm wondering if external BBs are interchangeable with different cranks?
Say will a Shimano Ultegra BB work with say FSA or Truvativ cranks?
11-12-10, 11:17 PM
If the spindle diameter is the same, they should be. FSA Mega Exo are the same as Shimano, but I do not know about Truvastiv.
11-13-10, 12:34 AM
The Shimano BB is compatible with FSA Aluminum Gossamer model not the CF models as far as the Truvativ cranks go I can't say.
The sram/truvativ GXP BB is wider than shimano and the non-drive side axle diameter is fractionally smaller than the shimano axle.
drive side is a perfect match.
also the GXP BB comes with 2x 2.5mm spacers which are needed, despite what the manual says, for 68mm BB shells.
I tried fitting a truvativ crank to tiagra BB, but the truvativ axle was too wide and also lose on the NDS.
now, with that said, I'm quite sure you can use a shimano cup on the drive side, the important side where the GXP BB is known to fail, and the GXP cup on the non drive side. BUT, I'm not sure if the protective tube will mate up properly.
Bottom line is that both BBs are inexpensive, and swapping the cups takes less than a minute. If you really want to swap cranks, just swap the cups when you do it. That also gives you a chance to clean out the BB and make sure there's no water in there.
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