Tire Size To Gear Ratio Calculator, This ratio, combined with your tire size and axle ratio, determines how fast the speedometer reads. To get that diameter from a size code, you convert the section width from millimeters to inches, multiply by the aspect ratio for sidewall height, double it, and add the wheel diameter. . Compare tire sizes, speedometer differences, RPM changes & recommended gear ratios. Use our gear ratio calculator to find the effective gear ratio your vehicle will have with a new tire size. This gear ratio and tire diameter chart is meant to give you an approximation of ideal RPMs at highway speed (65 mph) for three situations: fuel economy, every day driving and increased towing power. Calculate the gear ratio based on tire size. Also calculated is the new gearing you would need in order to return back to your original gear ratio when going to a bigger or smaller tire. ) Motorcycle speed and sprocket calculator with bike database for gearing, sprockets, tires and chains of over 1900 bikes. Supports P-metric & inch sizes for trucks, cars & motorcycles. whvxo, aenl6j, 83hn, euj, teny0, 0i, 1zs, h7, rawvb, msu,