Shimano BB91-41 Bottom bracket PAS success

Tarmacexpert1962

Finding my (electric) wheels
Apr 29, 2018
11
10
62
Esher
Finally managed to adapt the Right hand PAS sensor to fit a Shimano BB91-41 Hollowtech Inboard Bottom Bracket on my Full Sus MTB, found a use for the Unimat Mini Lathe and managed to machine out a 50mm hole as the BB91 is quite large, I adapted the Hollowtech crankset by replacing the Granny 22T ring with the PAS Disc and then fitting a 32T middle and 44T Outer ring, the clearance for the Sensor is very tight around the downtubes etc so I fitted it on the very bottom of the frame with a self tapping screw and Epoxy, its actually on its side but with just 1mm clearance it picks up the signal faultlessly. Just does go to show how non standard BBs with very restricted space can be converted, I would not have thought it viable unless I had done another conversion first, so with 11-36 Ten speed rear freewheel it will pretty much climb anything off road and has does not spin out at higher speeds . Next project is to convert the Sons Full Suspension Ghost with a SRAM GXP Bottom Bracket ready for the Brecon Beacons in March.IMG_0568 (002).JPGIMG_0569.JPGIMG_0570.JPG
 

jarob10

Esteemed Pedelecer
Jan 22, 2017
270
83
51
Uk
Good work. Next challenge is mounting the sensor

I managed to find a (vastly overpriced) bracket online. Does the job very well though, but the sensor needs coating with liquid insulation tape to avoid water ingress

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Laser Man

Pedelecer
Jul 1, 2018
200
127
Michelmersh SO51
WoW! I thought mine was tight enough and I didn't have to contend with a big suspension bush in the way.

I did manage to keep my granny ring though - the PAS disc is glued to the granny with a spacer so that the PAS is *just* clear of the chain.