Tire Rolling Radius Calculator | Effective Radius Under Load
Estimate a tire's rolling radius (effective radius from axle to ground under load based on P-Metric specs). Important for actual travel distance and gearing.
The rolling radius of a tire is its effective radius from the center of the axle to the ground when the vehicle is stationary and the tire is under its normal load. It's slightly less than the tire's unloaded (free or static) radius due to the deflection of the tire under the vehicle's weight.
Why is Rolling Radius Important? - **Accurate Speed & Distance:** Vehicle speedometers and odometers are calibrated based on the rolling radius. Changes to this radius (e.g., due to different tire sizes or pressures) can lead to inaccuracies. - **Gearing Calculations:** The effective gear ratio of a vehicle is influenced by the rolling radius. - **Vehicle Dynamics:** It plays a role in suspension geometry and how the vehicle interacts with the road.
This calculator estimates the rolling radius based on standard P-Metric tire dimensions. It first calculates the unloaded radius and then applies a common approximation (typically around 97% of the unloaded radius) to estimate the loaded rolling radius. Actual rolling radius can also be affected by tire pressure, load, speed, and specific tire construction.
- Enter the tire's Section Width in millimeters (e.g., 225).
- Input the tire's Aspect Ratio as a percentage (e.g., 45).
- Enter the Rim Diameter in inches (e.g., 17).
- Click the "Calculate Radius" button.
- The results will display the unloaded (free) radius of the tire and an estimated rolling radius (under load), both in inches and millimeters.
All tools and information provided on TireCalculatorHub are for informational purposes only. Calculated rolling radius is an estimation. Always consult with a qualified professional or refer to manufacturer specifications for precise data.
TireCalculatorHub is not liable for any damages or issues arising from the use of information or tools on this website.