Tyre rolling resistance and tyre rolling loss: a theoretical and experimental study based on a new trailer

The aim of the paper is to clarify the semantic and thus the difference between tyre rolling resistance and tyre rolling loss. Reference is exclusively made to longitudinal forces. The focus is on which are the actual forces and moments that cause a dissipated power during tyre rolling. The equilibrium equation for rotation of the wheel is unable to describe which are such actual forces and moments. In accordance with the existing literature, the power balance of rolling tyre is more suitable to identify the actual forces and moments causing dissipated power. We propose to refer to “rolling resistance” when the longitudinal slip is vanishing or low and to refer to “rolling loss” when the longitudinal slip is relatively high. A new index defining the rolling loss is proposed, namely the tyre rolling dissipation index (TRDI). The theoretical investigation is substantiated by an experimental activity performed via a new trailer for tyre testing. The rolling resistance torque, the external applied torque, the wheel axle height, the longitudinal force at the hub and the kinematics of the rim have been measured and combined to describe the TRDI. Results shows that tyre rolling loss increases as a braking torque is applied to the wheel and the effect of the TRDI is shown as function of longitudinal slip. A practical rule is proposed, stating that the ratio of tyre dissipated power to the total dissipated power is nearly equal to the longitudinal slip.