This calculator requires the use of Javascript enabled and capable browsers. 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 ration, the final transmission gear ration (usually 1.00) and the tire diameter, ground to top of tire as mounted. Click on Calculate for results. The first speed value returned is for the values you have entered. The additional values are based on the same factors except for the possible change of the ring gear and pinion value indicated. The default values are for a typical V8 small block Chevrolet vehicle, however you may enter any legal 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. We do assume safe tire air pressure and tread. The calculator does not take into consideration any drive train loss, road and weather conditions or driver skills. We also have a calculator for speedometer correction after tire or wheel size changes or after ring gear and pinion changes. You might also want to know how to calculate a ratio for the ring gear and pinion, or the potential speed for a given set of driveline equipment specifications. We urge you to drive safely.
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