The effect of load-dependent tyre friction and aerodynamic cross-flow forces on the g-g maps and minimum-lap-time of motorcycles

A three-dimensional quasi-steady-state free-trajectory method based on semi-analytical g-g maps has been recently proposed to simulate the minimum-time manoeuvring of road vehicles. A number of assumptions, such as identical tyre-road friction coefficients on front and rear tyres and negligible aerodynamic cross-flow forces (i.e. downforces and sideforces), were enforced in the case of motorcycles to keep the g-g maps semi-analytical. Such assumptions are lifted in this work and their effect on the g-g maps of single-track vehicles is analysed, together with the consequences on the related minimum-lap-time simulations. The examples of application are carried out on the Mugello circuit and compared with previous findings in the literature. It is found that different friction coefficients on tyres call for different braking strategies to extract the maximum performance of the vehicle (when compared against the case with equal friction coefficients), while aerodynamic downforces can reduce stoppie and wheelie problems, improve acceleration and braking performance and increase the maximum lateral acceleration achievable. However, if the resulting cross-flow force lies on the plane of the bike the maximum lateral performance could be reduced, depending on tyre properties.