Light Truck Tire Traction Properties and Their Effect on Braking Performance

Tire traction test data has shown empirically that peak skid number dry pavement traction performance of bias ply tires is inversely proportional to the dynamic instantaneous tire load and is a function of inflation pressure. A modification to classical braking theory, which assumes constant traction coefficients at the tire-road interface, is therefore required to obtain maximum theoretical unlocked wheel vehicle deceleration. Optimum brake proportioning between front and rear axles is dictated by the maximum braking force which, with respect to each axle, can be generated at the tire-road interface. The inclusion of peak traction coefficient normal load sensitivity significantly modifies classical theory and changes the selection of brake force balance required to attain maximum theoretical deceleration capability. The importance of the effects of tire traction load sensitivity on the requirements of FMVSS 105-75 is discussed in this paper.