Hi Don and
to the forum.
Check out
this thread for more details of fitting wide rims onto GM hubmotors.
Unfortunately, powering multiple motors from a single controller is not a good idea with brushless motors. It would have been an option with the old style DC brushed motors as long as the total motor load didn't overload the controller.
With brushless motors you would have a major problem trying to keep the AC phase voltage in time with the three phases of each motor.
You will need to use four separate controllers controlled by one set of controls
(throttle and brake etc.) like the four Magic Pies used here:
With multiple motors
(each one with its own controller) you need to make sure that the battery is capable of supplying the total current, or you may find that the battery's
BMS will cut out completely when the motors are placed under high load.
You presumably will be looking for a motor with strong torque, in which case the Magic Pie would be the obvious choice, but you would need to decide which option to use:
- MPII with separate external controllers
- MPIII with internal controllers
- MP4 with internal controllers
The external controller option is probably going to be a lot messier to install, but if you decide to use the internal controller I would suggest the MPIII might be a better choice than the MP4
(for your proposed application) because the slow speed take off is much smoother and more controllable than the MP4, and the electromagnetic dynamic braking would work at a much slower speed too.
You may be interested to know that the wider cast alloy rim on the 20" Magic Pies can be fitted with 16" motorcycle tyres:
So you could avoid all the hassle of lacing up modified wide rims and just use some 3.50-16 off road motorcycle tyres for extra grip:
The smaller overall diameter of the 20" Pie would also allow better use to be made of the motor torque for climbing steeper inclines, and it would also produce a stronger electromagnetic dynamic braking force.
Alan 
