Bafang G310 with Shimano 8/9/10/11 speed MTB cassette

cellmate

10 mW
Joined
Nov 15, 2018
Messages
25
Hi all,

I'm considering converting a 135mm dropout CX frame to an ebike using the G310 motor. The current drivetrain is a 10 speed shimano road cassette in the back.

I'm not sure what to make of this blurb from the Grin info page for the motor: https://www.ebikes.ca/product-info/geared.html#bicycle-fitment

Cassette Stack Height: With a 9 or 10 speed freehub, an additional 12mm washer is sometimes needed on the right side to accommodate the larger gear stack and have the chain clear the dropout. This will increase the OLD to 139mm.

If you look at the bottom half of this diagram:
https://bikerumor-wpengine.netdna-ssl.com/wp-content/uploads/2012/05/DT-Swiss-Shimano-11-speed-hub-diagram2.gif
you can see that the 10 speed shimano road cassette has a 35mm freehub body which hasn't changed in decades; in fact that same freehub body is also used for 7 (with spacer), 8, 9, 10, and 11 speed Shimano MTB cassettes.

The G310 has the exact same 35mm freehub body, specifically marked as a Shimano 7-10:
https://www.ebikes.ca/documents/MG310.pdf

You can see here that 8/9/10 speed MTB all have the same width of cassette (11 speed mtb is the same, road is not):
https://www.bikeman.com/bicycle-repair-tech-info/bikeman-tech-info/1640-how-many-gears-can-i-put-on-this-thing

So my questions then:
  • Why would I ever need a spacer? The furthest-right cog (smallest) is always the same size at 11T and always in the same place regardless of the cassette.
  • Why a 12mm spacer? That's huge!!! (did they mean 1.2mm?)
  • Can I expect my existing 10x road cassette to work without spacer?
  • If I ever do a flatbar conversion and move to a MTB 1x11 drivetrain, can I expect an 11spd MTB cassette to work without spacer?
  • Thoughts on stretching aluminum 135mm dropouts to 138mm?
 
The G310 has a 35mm freehub. 9-11 speed MTB cassettes also are 35mm wide and will fit (verified with 11-speed by me). 11-speed road cassettes are wider and will NOT fit.

The motor is 138mm wide. Regardless of number of speeds, the chain might hit the right dropout when it's on the smallest gear. Therefore, a 1.5mm wide washer is supplied to be added to the right side, which makes the motor 139.5mm wide (not 139mm as in the decription).

The 12mm here refer to the inner diameter, not the width of the washer. The description also confused me at first.

This 1.5mm washer also robs some interface from between the anti-rotation tabbed washer and its axle seat. Ideally, instead of using the 1.5mm washer, one would machine a custom tabbed washer that is a bit wider itself.
 
Thanks for the confirmation!

That matches what I suspected. I actually managed to confirm it yesterday myself by popping by at Grin with an 11speed mtb cassette and doing a test fit. It fit perfectly without the extra spacer into my CX frame.

Ordered the kit! Stoked!
 
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