What is the difference between the BB91-41A and the BB91-41B bottom brackets?

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TonyM
Posts: 3376
Joined: Thu Jan 22, 2015 4:11 pm

by TonyM

Hi,

I would like to replace the bottom bracket of my 2012 Scott Scale XTR.
The bottom bracket bearings have printed on it "Shimano SM-BB91-41".
The length of my bottom bracket shell is 89.5mm and there is 2.5mm spacer on the right side also, so in total 92mm.

But Shimano sells the SM-BB91-41A and the SM-BB91-41B....(no "A" or "B" printed on the bearings on my bike)
What is the difference between the "A" and "B" version??

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TheRookie
Posts: 926
Joined: Wed Jan 18, 2012 4:23 pm
Location: Midlands, United Kingdom

by TheRookie

The shimano tech docs are a wonderful source, worth bookmarking as its faster than a forum. http://si.shimano.com/#/
Your doc
http://si.shimano.com/pdfs/ev/EV-SM-BB91-2987A.pdf

The difference is the spacer (and matching tube length), you could buy either and use your existing internals if they are different, its not clear if your current spacer is external or internal as shown in the doc?
Impoverished weight weenie wanna-be!
Budget 26" HT build viewtopic.php?f=10&t=110956

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TonyM
Posts: 3376
Joined: Thu Jan 22, 2015 4:11 pm

by TonyM

TheRookie wrote:The shimano tech docs are a wonderful source, worth bookmarking as its faster than a forum. http://si.shimano.com/#/
Your doc
http://si.shimano.com/pdfs/ev/EV-SM-BB91-2987A.pdf

The difference is the spacer (and matching tube length), you could buy either and use your existing internals if they are different, its not clear if your current spacer is external or internal as shown in the doc?


Thanks! :thumbup:

My spacer is external.

I still don't understand the different - beside the spacer - between the "A" and the "B" version :? Or is the only difference that the "A" version has a spacer?

TheRookie
Posts: 926
Joined: Wed Jan 18, 2012 4:23 pm
Location: Midlands, United Kingdom

by TheRookie

The internal spacer and the length of the tube, which is longer on the spacer version at a guess.

As the cranks are the same, if you have an external spacer you probably don't have an internal one (hence same total width).

But I'm the person using an MTB BB on a Road bike having cut the flange off the spacer tube so it can be inserted further to achieve the same width as a road BB.
Impoverished weight weenie wanna-be!
Budget 26" HT build viewtopic.php?f=10&t=110956

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