Smoke said:
I want something that has 40 mph capability when I really need it (trying to avoid getting hit by a car), 25-30 mph cruise, maybe up to 35 mph if it works out and enough torque in low gear that starting from a stop on a slight incline is easy with pedal assist, even when total bike + rider + cargo weight approaches 500 lbs (probably using an Xtracycle style side car to carry about 200 lbs of that total).
At those speeds with that load, you are going to want as large a diameter wheel as you can get, with as big a tire as you can get, and preferably full suspension, or at least suspension on the cargo end of things.
If you don't, then antyhing other than perfectly smooth roads is likely to do some damage to your wheel, if not outright destroy it or cause a crash, depending on conditions.
I've got two rear wheels on SB Cruiser for the cargo area, and it's total weight is probably about the same as your goal, and I've damaged rims on holes at only 20MPH (and less) with no suspension, 16" Shinko SR714 2.5" tires on ex-Zero-MC rims. Didn't break any spokes, but on the worst one the wheel as a whole was damged enough to be untruable, though it's still rideable, if wobbly, and the tire stays on the bent rim.
Don't want to imagine what that impact would''ve been like at 30 or 40MPH--it took a fair bit of velocity off my speed at that moment, and converted that into energy focused on the impact point of the wheel and edge of hole.
Same thing happened with a rain-covered invisible hole on my smaller longtail CrazyBike2 with the same rear wheel type (but a bicycle tire).
On SBC, I've also broken two different motors' axles from impacts under load (>500lbs total, probably 600+), and another motor's axle broken from torque testing a new controller.
Bigger diameter will go over/thru holes smaller ones won't, and ride smoother under the same conditions the smaller doesn't.
The other thing you need is great traction (and big contact patches) for your brakes, which will have to be really good, to be able to stop you from the highest speeds you will be reaching, while fully loaded at max weight.
FWIW, CB2 uses around 80A with 2WD to reach 20MPH in about 4 seconds at probably about 400lbs total. SB Cruiser uses around 120A with 2WD with heftier motors to do the same thing at 500lbs. IIRC another 40A+ on top of that gets me about a second less, using the SFOC5 controller from Incememed under testing, on the right wheel, and a modded generic on the left.