Tire Size Math
Tire size and gear ratio math.
Tire size calculator →Diameter, width, sidewall, circumference and revolutions per mile from a size like 265/70R17.
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Tire size comparison
Two sizes side by side: the diameter and width difference, and the speedometer reading after the change.
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Gear ratio calculator
The axle ratio from ring and pinion tooth counts, and engine RPM at highway speeds.
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Effective gear ratio and RPM
How a tire size change shifts the effective axle ratio and engine RPM at a given speed.