In this paper, validation of a model for the speed dependency of friction is presented. Based on the shape of the friction – speed curve, the model assumes that calculation of friction at any speed would need an estimate of friction at very low speed, and the knowledge of its variation with speed described by the Stribeck curve. Two existing models developed at LCPC are then coupled to predict friction versus speed from the following characteristics: road surface macro and microtexture, rubber relaxation time, wheel slip, tire tread depth and water layer thickness. Description of the models is given. The unified model is validated on data obtained from experimental campaigns conducted in France from 2001 to 2003. On 30 sections, including test tracks and trafficked roads, friction was measured by means of the British Pendulum and the front-wheel braking method with the LCPC instrumented car giving μpeak and μlocked. Road microtexture profiles were measured by means of LCPC static laser systems. Profile characteristics are given. BPN and μpeak values were compared with results predicted from road microtexture and tire-rubber properties. For μlocked, which is obtained at higher speeds, its value was deduced from μpeak using the modelled Stribeck curve. Results are discussed.
Prediction of tire/wet road friction and its variation with speed from road macro- and microtexture, and tire-related properties