Performance Equations

The following equations and rules apply only to 4-cycle engines powered by pump gasoline. The equations have been simplified for ease of understanding. Answers will approximate, but generally close enough for use as a guideline.

It is recommended that you round your result to the nearest hundreth, ie. 4.118325 = 4.12

Gear Ratio= Rear Axle ratio multiplied by Transmission gear ratio. (Tranny list below) Ex: 4.11*1=4.11 (rear axle=4.11) (1=1:1, fourth gear in some trannies.)

MPH
Tire Radius	RPM	Rear End Ratio	Transmission Gear Ratio	=MPH

RPM
Rear End Ratio	Transmission Gear Ratio	MPH	Tire Radius	=RPM

Calculated Gear Ratio (Trans. gear multiplied by rear end gear)
Tire Radius	RPM	MPH	=Gear Ratio

Transmission Gear (relative to variables of calculated gear ratio equation)
Calculated Gear Ratio	Rear end ratio	=Transmission gear ratio

Rear end gear (relative to variables of calculated gear ratio equation)
Calculated gear ratio	Transmission gear	=Rear end gear

Performance Equations

It is recommended that you round your result to the nearest hundreth, ie. 4.118325 = 4.12

Gear Ratio= Rear Axle ratio multiplied by Transmission gear ratio. (Tranny list below) Ex: 4.11*1=4.11 (rear axle=4.11) (1=1:1, fourth gear in some trannies.)

Tire Radius= Distance, in inches, from the center of the tire to the ground.

MPH

RPM

Calculated Gear Ratio (Trans. gear multiplied by rear end gear)

Transmission Gear (relative to variables of calculated gear ratio equation)

Rear end gear (relative to variables of calculated gear ratio equation)

Tire Radius