Friction inside wheel hub bearings: evaluation through analytical models and experimental methodologies

This paper presents an experimental methodology which can be adopted to measure the friction torque of the bearings in the wheel hubs of passenger vehicles. The first section of the paper highlights the reasons why an experimental device is necessary to have an objective evaluation of the performance of the bearing in terms of friction. In particular, the high level of approximation of the current formulas for the estimation of the friction inside a single bearing is discussed and demonstrated. An analytical methodology for the evaluation of the distribution of the axial load between the two bearings of the wheel hub is presented. However, its practical application for the precise calculation of the distribution of the load has to be checked through experimental tests. The following part of the paper is focused on the possible solutions which can be adopted to conceive a test rig to measure friction inside the bearings of wheel hubs by considering the effect of the real loads acting on the hubs of the vehicle (due to the forces between the tires and the road surface). The most efficient solution of test rig is developed and implemented for the evaluation of the friction of the bearings of a 3-wheel low consumption vehicle. This solution, which can be properly sized according to the considered application, can be extended also to the evaluation of the performance, in terms of friction, of the hubs of series production passenger cars.