The measurement of a road surface friction coefficient is significant to improve the advanced driver assistance system (ADAS). ADAS uses the information from wheel sensors, acceleration sensors, yaw rate sensors, etc. However, it is difficult to measure the road surface friction coefficients accurately with these sensors. Therefore, various studies focusing on tires that are the only part contact with the road for a car have been conducted to measure the road surface friction coefficients. However, tires are susceptible to degradation and require frequent replacement. Therefore, this study focuses on a wheel and proposes a method to measure road surface friction coefficient from strains induced in the surface of a wheel. First, we clarified the relationship between the strains on a wheel and the loads acting on the tire from the grounding surface by using an experimental apparatus capable of simulating slip running. Second, a simple method of measuring road surface friction coefficients was proposed using the obtained relationship and indicated the measurement accuracy of road surface friction coefficients at various ground plates.
