Modifications to mount RH212

[mszil]

Hi all,
Got a 9C RH-212 from ebikes.ca awhile back and finally have some time to mount it correctly. Noticed it is difficult to align in my frame - it appears to be designed for 135mm dropouts and the drawing indicates 41mm for the cassette - but there is a stand-off at the rear of the freehub (closest to the motor) that spaces the cassette a couple mm off. Normally this wouldn't bother me at all, but once mounted the smallest cog is striking the frame. The provided 3mm thick washer with 10mm flats doesn't fit through the cassette lockring - so will need to remove ~1.5mm off the diameter of that, removing its yellow zinc coating (given standard lockring dimensions, this part seems designed to not fit). Even once the washer is in place I suspect the cassette will be too close to the frame to use the smallest cog so I'm also grinding ~1.5mm off the step at the rear of the freehub so the cassette moves further down. If needed I'll also grind a bit off the lockring but I think everything should still mount. I suppose I could add washers but I'm already pulling the frame a couple mm to mount it this way with just the single washer on the cassette side and don't want to push my luck with Al frames. Seems like a nuisance. Is that normal for this motor? Have others had to do similar tweaks or is my axle somehow off - I'm pretty sure it's not adjustable like the old cup-cone ones might have been.

Thanks for any feedback -
Markus

 

[E-HP]

Is that normal for this motor?

It's normal for most 135mm dropout motors, which is why Grin sells these:

Spacer Washer 3mm

3mm Stainless Steel washer for spacing hub motor axles..

ebikes.ca

If you're running a hub motor, you might not need all of those gears, so if the clearance is enough for the cassette to spin, but not enough to allow the chain to uses the smallest cog, you could restack the cassette to move the smallest cog, and any of the gears you normally use, so that they have the best chainline.

 

[mszil]

It's normal for most 135mm dropout motors, which is why Grin sells these:

Spacer Washer 3mm

3mm Stainless Steel washer for spacing hub motor axles..

ebikes.ca

If you're running a hub motor, you might not need all of those gears, so if the clearance is enough for the cassette to spin, but not enough to allow the chain to uses the smallest cog, you could restack the cassette to move the smallest cog, and any of the gears you normally use, so that they have the best chainline.

Thanks - guess I missed that when putting the order together - something I would have hoped they could have flagged - probaby quite expensive to get it now when ordering from New Zealand. Still wonder why they (both 9C and Grin) include hardware that doesn't seem like it could fit (is there some common arrangement where the included flatted-washers work?). I'm hoping to use the motor regularly on one bike and occasionally on a 2nd tandem for touring - so it would be nice if I could swap out the wheel without too much hassle - and trying to get the 9sp cassette to 8sp seems like more work than trying to grind the freehub (at least until I screw something up). Anyway, currently grinding that washer down. See how things turn out...

 

[E-HP]

Still wonder why they (both 9C and Grin) include hardware that doesn't seem like it could fit (is there some common arrangement where the included flatted-washers work?). Anyway, currently grinding that washer down. See how things turn out...

I agree in principle, but on the other hand, my ebay MXUS motor came with the same hardware and had the same issue, and I used the same solution. The positive part is that at least Grin does offer a solution. I used some masking tape on a drill bit and sanded using my drill to spin the washer against my bench disc sander. I remembered to include a couple in my next Grin order though. (which was good, since the Leaf motor I'm using now, came with the same hardware, or lack of)

 

[tomjasz]

Ask them to send by regular mail. They have done so for me.