The relation between contact patch geometry and the mechanical properties of motorcycle tyres

The mechanical properties of motorcycle and scooter tyres have a large influence on the handling and stability of these vehicles. When a two-wheeled vehicle moves along a curvilinear path, there are large camber angles (up to 50◦); hence, tyres have a curved cross-section and the contact patch moves and changes its shape when the roll and steer angles are modified by the rider. This paper describes experimental research aimed at studying the influence of the camber angle, vertical load and inflation pressure on the shape of the contact patch and the forces and moments of the tyres. The experimental tests were carried out by means of a rotating-disc machine. The contact patches were measured by making use of a pressure-indicating film. The camber force and twisting torque were related to the vertical load and inflation pressure through the dimensions of the contact patch. Newbestfitting equations were developed starting from the brush model. Many experimental results dealing with front and rear tyres are presented and the merits and limitations of the best-fitting equations are discussed.