This calculator is designed to give the potential speed values of a vehicle, based on the RPM of the engine, the ring gear and pinion gear ratio, the final transmission gear ratio and the tire diameter, ground to top of tire as mounted.
The default values are for a typical V8 small block Chevrolet vehicle, however you may enter any value you wish.
The default values yield a highway cruise speed of about 65 MPH.
The higher the RGP ratio, the lower the top end speed but faster acceleration and more pulling power.
The same is true of the transmission final gear ratio. The higher the engine RPM, the greater the potential speed at the cost of fuel, heat, friction, and engine longevity.
Although there is a point of diminishing returns, the larger the tire diameter, the higher the potential speed.