Parameterisation and modelling of large off-road tyres for on-road handling analyses

Abstract Very few off-road vehicles are used exclusively under off-road conditions. Good off-road mobility dictates large high aspect ratio tyres with aggressive tread, low inflation pressures, soft suspension for good comfort as well as other vehicle parameters including large ground clearance and the related high centre of mass. This results in less-than-satisfactory vehicle handling and high rollover propensity on hard terrains at higher speeds. In order to simulate vehicle handling and roll over propensities, on non-deformable terrain, tyre characteristics in the form of side-force versus slip-angle curves, as well as suitable tyre models are required. For large off-road tyres these characteristics are not readily available. Tyre manufacturers either do not have these characteristics, or do not openly publish them. Similarly, the majority of tyre models have been developed and validated for passenger car tyres and their applicability to large tyres are unknown. The purpose of this study is to measure side-force versus slip-angle characteristics for a Michelin 16.00R20 XZL tyre – typically used on off-road trucks. The data is used to parameterise Fiala, UA (University of Arizona), Pacejka89 and FTire models. Simulation results are compared to both steady state and dynamic handling test results to determine the accuracy of these models.