Tire Rolling Radius Evolution with Tread Depth and the Implications for Tire Replacement on All-Wheel Drive Vehicles

All-wheel drive (AWD) and four-wheel drive (4WD) vehicles are becoming more prevalent in the market today. However, it is not well understood what the correct practice is when only one tire on the vehicle needs to be replaced. There are various recommendations and practices provided by tire dealers and car manufacturers to the consumer. The most common recommendation is to replace more than a single tire and match tread depths across all tires. The basis for this recommendation is the idea that tires with different tread depths will have a different number of revolutions per distance traveled due to differences in rolling radius. Mixing tires with different tread depths may cause extra wear or damage to the drivetrain components because, on a vehicle, the tires must rotate at different speeds to travel the same distance. In this study, the rolling radius of tires is measured on vehicle to understand the impact of tread depth, tire brand and model, and inflation pressure on the rolling radius. It was found that the rolling radius is not as sensitive to tread depth as it is to tire brand and model or even inflation pressure. Therefore, matching tread depths is not the most relevant criteria when replacing a single tire or tires in pairs. It is more important to match tire brand and model and maintain proper inflation pressure to ensure equal rolling radii across all tires.