Influence of Changes in Stiffness and Damping of Tyre Wheels on the Outcome of the Condition Assessment of Motor Vehicle Shock Absorbers

Abstract

This article deals with the influence of the elastic-damping properties (energy losses) of tired wheels on the results of the evaluation of the technical condition (dynamic properties) of automotive suspensions carried out on the diagnostic line. The purpose of this paper is to point out the inadequacies of test stands for assessing the technical condition of vehicle suspensions. The diagnostic line used in the testing featured two testing stations. The test object was a passenger car with hydro-pneumatic suspension. This enabled the conducting of suspension tests for two settings (comfort and dynamic positions). The tests were conducted for four different air pressures in the tyres of tired wheels. This made it possible to determine, for each wheel, four graphs of the load versus tyre deflection (radial stiffness characteristics). These graphs were used to determine the values of the stiffness coefficients, energy loss, and damping characteristics as well as to identify the correlation between the directional coefficient of the regression line of the elastic and damping characteristics of the tyres and the indices characterising the damping properties of the suspension of the test car. This paper shows that the result of the shock absorber condition assessment is significantly influenced by the elastic and damping properties of the tired wheels, caused by changes in tyre pressure.