Shimano Hollowtech II External Bottom Brackets

richj8990

100 W
Joined
Jan 21, 2020
Messages
277
Hello everyone,

My candidate bike for a Bafang BSS02 mid-drive conversion has a threaded / English / BSA BB30, 73mm. Part number is Shimano XTR SM-BB93. That I do know (I didn't install it). The question is, and yes it's probably dumb, but when they say "You need to remove the bottom bracket"...when it comes to something like Hollowtech II, what they really mean is that you remove the two external bearing cups on the outside of the frame, and leave the inside alone, correct? You don't have to take the whole thing out, just the outside bearings, correct? And then it looks like Bafang (or maybe that was just CYC) had their own kit bearings to screw back on to the frame later during mid-drive axle installation. First time for me doing a mid-drive conversion...this is the only iffy part of it, the rest looks pretty straightforward.

If that's the case for just removing the two external bearings, all I have to do is buy the $10 BB removal tool and I think I'm good to go for the installation. I've more or less done an entire front hub drive by myself, and this doesn't seem any more complicated than that (considering the geared hub drives with external controllers have a gazillion wires to deal with). Otherwise, if the whole BB has to come out, that's something a bike shop should really do. Thanks for your help on this otherwise simple question.
 
There's nothing else inside the bb. Just those 2 cups and the axle.
 
mxlemming said:
There's nothing else inside the bb. Just those 2 cups and the axle.

There's a little plastic sleeve between the cups that serves as a crap shield.
 
Chalo said:
mxlemming said:
There's nothing else inside the bb. Just those 2 cups and the axle.

There's a little plastic sleeve between the cups that serves as a crap shield.

And some air. Don't forget the air.
 
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