A study of the cornering power by use of the analytical tyre model

A new analytical tyre model for the cornering power (CP) and the self-aligning torque power (SATP) is proposed on the basis of the Fiala model. In a pneumatic tyre, the self-deformation by the transmission of force and torque is so large that it influences recursively the force and torque generation during cornering. Then the CP and SATP have negative feedback loops; as the CP and SATP increase, the steering transmission loss due to tyre self-deformation also increases, reducing further increments in the CP and SATP. The present model, the CP-SATP system model, analytically describes the force and torque transmission with feedback loops by taking into account not only the shear deformation of the tread rubber and the in-plane belt deflection, but also the out-of-plane sidewall rotation. As with other practical systems with a negative feedback loop, the CP and SATP feedback sustain the CP and SATP output levels at a higher vertical load and approximate the measured load dependences of the CP and SATP with high accuracy. Although the sidewall rotation feedback due to the SATP has not been considered in conventional cornering studies, its contribution in recent radial tyres is shown to be larger than that of belt deflection due to the CP.