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Rear hub motor with 14mm axle/10mm flats ok in regular 12mm/10mm dropouts/fork-end?

TheBeastie

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Jul 27, 2012
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2,097
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Melbourne Australia
I am doing a fat bike conversion and ordered a rear hub motor that was supposed to be with a standard rear axle of 12mm with 10mm flats.
I laced the motor into the rim and only after when trying to put the hub motor wheel in I noticed it didn't fit very well into the fat bikes frame dropouts, as shown in the pictures. Turns out they sent me a 14mm axle rear hub motor.

I double checked the chinese ebike website I ordered the motor from and 14mm rear hub motors isn't even an axle size they sell. So I am suspicious they had this 14mm axle sized hub motor sitting around and decided to just dump it on me.
I guess my main question is, will it work OK anyway? I guess there is a limit where it is dangerous, if I just use the LCD/controller settings at no more than something like 600watts of power will it be OK?

Here are a bunch of photos of the 14mm axle in the drop out that is meant for standard 12mm by 10mm axle.

I am pretty disappointed in the seller, I make a total $1600 AUD order and this is what I get.. I could have bought a complete electric fat bike locally for that money, it's so much cheaper than it used to be, but I thought it would be nice to build something that I wanted specifically..
I ordered some front fork 14mm front torque arm and going to try and make it work but I noticed standard front fork 14mm torque arms don't fit very well on a rear drop out, does anyone have any links to 14mm torque arms designed for the rear instead of front forks? As it doesn't seem to be a typical thing.
Thanks
 

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With a small round file you can carve out some material from the dropout (both "corners") to match the radius of the axle. This will allow it to seat further into the dropout. As long as the axle nut does not interfere with the derailleur mount, and with quality TAs*, you are good.

Take your time with the filing. Do not square the radius (by using a flat file, for ex.) as the corners would act as stress risers that make a crack more likely. Keep it rounded, but match the new axle larger radius.

20240502_012418c2.jpg

*Grintech TAs are well-made and designed. They are up to the job.

DO NOT use anything that resembles their "TorqArm_V1 / DISCONTINUED" model!!!

Comparison:
 
With a small round file you can carve out some material from the dropout (both "corners") to match the radius of the axle. This will allow it to seat further into the dropout. As long as the axle nut does not interfere with the derailleur mount, and with quality TAs*, you are good.

Take your time with the filing. Do not square the radius (by using a flat file, for ex.) as the corners would act as stress risers that make a crack more likely. Keep it rounded, but match the new axle larger radius.



*Grintech TAs are well-made and designed. They are up to the job.

DO NOT use anything that resembles their "TorqArm_V1 / DISCONTINUED" model!!!

Comparison:

Just an update..
Thanks for the advice and followed it. I decided to get the Grin V5 torque arm for both sides, and it worked out great in terms of fit and locking in the motor axle safely. 1718679194441.png1718679108034.png
 
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