RPM Formula

This Formula allows you to calculate how many RPM's your engine will need to turn for you to go a certain MPH with those new tires and gears. Just plug in the MPH you want to run at  with your trans and axle gear ratios. Then put in your true tire diameter (as measured on the vehicle, not the number marked on the sidewall) The RPMs will be calculated for you.

MPH

True Tire Diameter

Transmission Final Gear Ratio

Axle Gear Ratio

RPM =