Rubber friction, tread deformation and tire traction

We study the role of rubber friction in tire traction with special emphasis on the load and velocity dependence of the friction coefficient. In the first part, we present some basic concepts of contact mechanics of slipping tires and analyze the influence of energy dissipation due to tread deformation on the friction force. Then, we apply a recently developed model of hysteresis and adhesion friction of rubber on self-affine road surfaces for estimating the load dependence of the kinetic friction coefficient in the contact area of slipping tires. In this context the impact of track morphology (sharp or blunt) on the kinetic friction characteristics is demonstrated. Finally, using the brush model for slipping tires we discuss consequences of the load dependence of the kinetic friction coefficient with respect to the overall tire friction and slip characteristics. We show that due to the presence of a load dependence of the local rubber-road friction coefficient the tread contact patch is globally never entirely in a fully sliding situation. The presented results yield a contribution to an improved physical understanding of the dynamic frictional contact of tires with road tracks during cornering and braking, especially in the case of cars equipped with Anti-Blocking Systems (ABSs).