Front or Rear hub motor??

[Gumboocho]

Is there any physical difference between a front hub motor & a rear hub motor? Can one take a rear hub motor & install it in a front wheel? Is it there there are some, but not all rear hub motors which can also serve as a front hub motor?

 

[harryS]

A typical front hub is 100mm wide between the forks. A typical rear hub is 130-140mm, with most at 135mm. The extra width is for the gear cluster, and even if you removed it, the rear motor usually wouldn't have enough threads on the axle to engage the fork.

The only time I've been able to use a 135mm motor on the front is with a 135mm fat tire fork, and the motor is so uncentered in the fork. the rim has to be spoked so it is located in the middle, This weakens it tremendously,