[thingstodo]

I went out to determine why the wheels on the truck measure out just under 30 inches in diameter, for about 94 inches around, but the ev calculator shows me that one revolution of the tire is more like 87 inches.

So I marked the tires with tape, and the ground with tape to show the starting point. I inflated the tires to 32 psi cold and pushed the truck forward one complete tire revolution. The answer - 87 inches. So I went another revolution and checked the total distance - OK - my tape measure is too short for that. So I measured 4 more tire revolutions and measured each. The results were between 86.5 and 87.75 inches.

I guess the side walls of the tire must flex quite a bit. I used a piece of network cable long enough to go from the starting position to the ending position and measured it in 12 foot chunks. 87 inches is close enough. That gives 13.85 inches radius.

I guess the ev calculator was right.

That 87 inch circumference gives just over 728 revolutions per minute at 60 mph. Just under 2500 rpm at 60 mph.

So 70 mph would be 2915 rpm. The motor is rated at 1770 rpm. That would require about 99 Hz.

At 99 Hz the torque output from 120 foot-lb (40 HP) would drop to about 72.

The smaller effective diameter should make the acceleration better, but it may hurt at the top end.