Overall Gear Reduction

IMPERIAL

The overall gear reduction is the RPM time the rolling radius of the loaded driving tyre divided by 168 times the vehicle speed in miles per hour

Where:

168 = Factor

RPM = Revolutions per minute of engine

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

METRIC

The overall gear reduction is the RPM time the rolling radius of the loaded driving tyre divided by 168 times the vehicle speed in miles per hour

Where:

2651.51 = Factor

RPM = Revolutions per minute of engine

r = Rolling radius of loaded driving tyre in millimetres

R = Overall gear reduction including both axle and transmission

KPH = Vehicle speed in kilometres per hour

Example:

Find out overall gear reduction of a vehicle where the motor speed is 1680 RPM, the rolling radius of loaded driving tyre is 381mm and the KPH is 24.