Torque arms

[roostersgt]

Could someone post up a few pics of the proper placement of where torque arms should be mounted on both a rear hub drive and front hub drive? I’m building both and have seen conflicting information. On the rear it seems the arm should be mounted below the chain stays, and on the front , behind the fork, not in front. Is this correct? Thank you.

 

[Freddy1]

Could someone post up a few pics of the proper placement of where torque arms should be mounted on both a rear hub drive and front hub drive? I’m building both and have seen conflicting information. On the rear it seems the arm should be mounted below the chain stays, and on the front , behind the fork, not in front. Is this correct? Thank you.

My take is you want the arm, if it tries to rotate, to place its load onto the frame, not onto the weaker retaining band/s e.g. hose clamps being popular. What ever side and position puts that potential axle rotation (opposite to the forward wheel rotation) against the frame is the right place.

 

[m@Robertson]

On the rear it seems the arm should be mounted below the chain stays, and on the front , behind the fork, not in front. Is this correct? Thank you.

Short answer is yes, if you are putting the arms on the non drive side.

Grin technologies torque arms are going to be more expensive but also of MUCH higher quality. Also, Grin has an excellent info page on how torque arms work which also answer your placement question. Note the 'V1' arm they show is widely copied and is junk relative to what else is out there in the world in 2023.

Grin Tech Torque Arm Info Page

Description of Hub Motor Torque Arm offerings from Grin Technolgies

ebikes.ca

One thing I have done on front motors is to always use two torque arms. One on each side and despite the fact that one of them can be argued to be on the wrong side, the fact that two are in place just plain locks the motor down in the dropouts whether it likes it or not. The two together are enough to counteract anything a 2 kw motor can throw at them. Just checked my build pics and the first set I did have been in place since 2018 on a chromoly fork.

Here's a rear one. Ignore the slight space above the bolt on this one. I actually slotted the arm a bit so the M8 sliding dropout bolt could fit thru it. Its not possible for it to slip. this is another 2kw peak motor (58.8v x 35a = 2058w). If you are using a more powerful motor than this you want to be upping your game beyond what I am doing here.