[What's_nitro?]

Thanks. It's really simple if you think about it. Figure out the circumference of the tire and how fast it spins, then simplify it into the proper terms. I divided by 8 because of your final dirve ratio of 8:1. So to get how fast the tires spin you take the motor's speed and divide it by the final gear ratio.

Example: With your 15:1 ratio- (rounded numbers)

Motor speed: 45000 rpm
Gear ratio: 15:1
Tire circumference: 15 in.

Divide your motor speed by the final gear ratio and you get 3000 rpm. Multiply that by the tire circumference and you get 45000 in. per minute. Then divide that number by 63360 in. per mile and you get 0.7102 miles per minute. Times 60 give you your speed of ~42 miles per hour.