Abstract
This paper presents a theoretical analysis of the influence of tyre characteristics on motorcycle manoeuvrability.
The analysis is carried out using a novel approach, developed by the same authors, called
the optimal manoeuvre method, which has been presented and demonstrated in former papers [1-4]. The method is an application of the optimal control, which consists in finding the solution of the equations of motion corresponding to the minimum time used for moving between given end-points. The solution must also comply with trajectory constraints that express all existing physical limitations, like lane borders, available thrust and tyre traction. This particular solution, once found, represents the fastest way for moving between the given endpoints satisfying all trajectory con-straints
( i.e.: the optimal manoeuvre) and provides a clear way of evaluating vehicle performance by means of a single scalar index.
This paper focuses on the influence of tyre camber and cornering stiffness of both front and rear wheels, and on the front/rear balance of the vehicle. Unlike cars and other four-wheeled vehi-cles, motorcycles undergo significant rolling, which in turn is responsible for large tyre camber thrust. Camber thrust may exceed what is needed for the steady turning. If this happens, wheels travel with negative side-slip. Understeering and oversteering may arise not only from unbalanced cornering stiffness, as in cars, but also from different camber stiffness of the wheels.
The paper presents an analysis of the time used by vehicles with different combinations of camber/cornering stiffness to complete a short race-like circuit. Results show that the camber stiffness of front and rear wheels has to be balanced to obtain faster vehicles, while the balancing of cornering stiffness does not the same importance. It is also shown that higher tyre stiffness is better.