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Calculate the correct speedometer driven gear.
Calculate driven gear teeth based on axle ratio and tire size.
Estimate tire revolutions per mile.
Get precise tooth counts for speedometer calibration.
The Speedometer Gear Calculator is designed for automotive enthusiasts and mechanics who have changed their vehicle's tire size or rear axle gear ratio. These changes often lead to an inaccurate speedometer. This tool helps you determine the correct driven gear tooth count to recalibrate your speedometer, ensuring accurate speed readings.
Input the number of teeth on your transmission's drive gear.
Input your vehicle's rear axle gear ratio (e.g., 3.55, 3.73, 4.10).
Input the total diameter of your rear tires in inches.
See the calculated driven gear tooth count and choose the closest available gear.
Enter the total height of your tire in inches.
When you change your vehicle's tire size or rear axle gear ratio, your speedometer will become inaccurate. Changing the driven gear in your transmission is a common way to recalibrate it.
The calculator provides the ideal tooth count. Since gears only come in whole numbers, choose the available gear with the tooth count closest to the calculated value.