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Discussion Starter · #1 ·
From research and a phone call with LBS it sounds like the difference between the Shimano BB91-41A and 41B is mountain vs road. Supposedly the Shimano rep said there was very little difference, but it appears that a 41A is for 86.5mm shells and 41B is for 89.5-92mm shells, which to me is a big enough difference.

I have a 2011 Giant Reign, and the best I can tell, the bottom shell measures 89.5mm. The existing bottom bracket only has BB91-41 on it with no A or B notation. Also, it has a 2.5mm spacer on the drive side. So, with this I'm assuming a total length of 92mm which would make it the BB91-41B size? However, the Shimano techdoc drawing shows only the 41A with the 2.5mm spacer which my bike has.

Anyone know what size I need? Does it even matter? - as I could probably use the existing plastic inner cover with the new outer bearings if I don't damage on removal.
 
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