Miles / Kilometres per Hour from Motor Speed

IMPERIAL

Vehicle speed in miles per hour is the rolling radius of loaded driving tyre multiplied by the motor RPM and divided by 168 times the overall gear reduction of the power train.

Where:

168 = Factor

RPM = Revolutions per minute of the motor

r = Rolling radius of loaded driving tyre in inches

R = Overall gear reduction including both axle and transmission

MPH= Vehicle speed in miles per hour

Example:

Find the MPH of a vehicle where the motor speed is 1680 RPM, the rolling radius of loaded driving tyre is 15 inches and the overall gear reduction is 10

METRIC

Vehicle speed in kilometres per hour is the rolling radius of loaded driving tyre multiplied by the motor RPM and divided by 168 times the overall gear reduction of the power train.

Where:

2651.51 = Factor

RPM = Revolutions per minute of the motor

r = Rolling radius of loaded driving tyre in millimetres

R = Overall gear reduction including both axle and transmission

MPH= Vehicle speed in kilometres per hour

Example:

Find the KPH of a vehicle where the motor speed is 1362 RPM, the rolling radius of loaded driving tyre is 400 millimetres and the overall gear reduction is 10