Tire Size Gear Ratio & Re-Gearing Calculator
Calculate your vehicle’s effective gear ratio after installing larger or smaller tires, and determine the exact replacement ring-and-pinion axle ratio required to restore factory power and speedometer accuracy.
Original & New Tire / Gear Specifications
Inches
Factory stock tire size (e.g. 31").
Inches
Aftermarket lifted tire size (e.g. 35").
:1
Existing differential ratio.
MPH
Dash reading for error check.
Required Re-Gear Axle Ratio
RECOMMENDED: 4.10 OR 4.56
4.21:1
Exact mathematical match to factory mechanical leverage
Current Effective Ratio
3.30:1
11.4% torque loss vs stock
Speedometer Discrepancy
+12.9%
At 65 MPH indicated = 73.4 MPH actual
Off-Road Gearing Recommendations
Factory Fuel-Economy Match:
4.10:1
Towing / Rock Crawling Target:
4.56:1