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BB89.5 vs BB92 Shimano bottom bracket (misterious 2.5mm spacer)

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BB89.5 vs BB92 Shimano bottom bracket (misterious 2.5mm spacer)

Old 05-04-22, 05:12 AM
  #1  
samatthias
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BB89.5 vs BB92 Shimano bottom bracket (misterious 2.5mm spacer)

Dear bikeforums.net community

As must of us know there are twho differen mtb shimano pressfit bottom brackets: 89.5mm and 92mm.
If we look carefully into the shimano techguide we see that the description mention that the 89.5mm ist for symetric frames and uses a 2.5mm spacet to become also 92mm total width.
The 92mm should be used with asymetric frames.

So my question is: Can someone explain me why there is 89.5mm + 2.5mm spacer version and a 92mm version? They both endup in a 92mm width.
From a numeric point of you that doesn't make sense at all.

I really don't get it - is there another tecnical mystery I overlooked or I still not able to catch?

Many thanks for your answers and your time spent replying me.

best regards
Matt
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Old 05-04-22, 11:15 PM
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duanedr 
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Originally Posted by samatthias View Post
Can someone explain me why there is 89.5mm + 2.5mm spacer version and a 92mm version? They both endup in a 92mm width.

best regards
Matt
Simple explanation: Because it's the bike business. The one new standard I do like is the T47 BB - FWIW. The benefits of threaded cups and a lot of volume for big spindles, bearings and internally routed cables (where required) is, dare I say, intoxicating. Yes, I'm 1.5 cocktails into the evening.

I find this helpful
FSA EasyBottomBrackets (fsaeasybottombrackets.com)
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Old 05-05-22, 04:55 AM
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dsaul
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One fits in a 92mm width bottom bracket shell and the other fits in an 89.5mm bottom bracket shell. The crankset has the same length spindle on both, so a 2.5mm spacer(outside the BB shell) is necessary to take up the extra space on the spindle.
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Old 05-05-22, 01:06 PM
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unterhausen
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Do they think you might need to move the chain line over that much? There was some bike I assembled that came with spacers and I forget where they intended for them to go. Mid-range Salsa, IIRC. The shop owner consulted with Shimano, but I don't think I ever heard the outcome of that
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Old 05-10-22, 06:45 AM
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samatthias
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Thanks a lot guys for your replies. I really appreciate your effort to help me.

best regards
Matt
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