Institut für Fahrzeugsystemtechnik

Physical Model of Tire‑Road Contact Under Wet Conditions


A physical model to describe the contact between rubber and a rough surface with water as intermediate medium is presented. The Navier–Stokes equations are simplified and surface properties are approached by the Abbott–Firestone curve to generate an approximative description of the water squeeze out between a visco-elastic rubber block and a macro-rough surface. The model is used to describe the pattern dependent wet grip performance of vehicle tires at moderate water heights between pure wetgrip and full hydroplaning. Influence of surface macro-roughness, water height, tire pattern, and vehicle speed on braking performance is considered in particular. For validation purpose, braking tests on two different surfaces were done at an inner drum test bench. Test results show good agreement with the theory presented.