Servo method for maintaining the wheel-sliding at an optimal level in order to achieve a maximum coefficent of adherance

Slaving method for a phenomenon, a parameter (Y) of which varies as a function of another parameter (X) according to a law with an increasing section, a maximum and a decreasing section. Accordingly initial values are measured or estimated, gradient values are determined between the point and the origin, coefficients are calculated directly or by regression and a target maximum value is determined using a predetermined invariant. Independent claims are also included for the following:- (a) A motor vehicle ground connection system; (b) a method for checking the operation of a sliding tire; (c) a method for testing a sliding tire; and a method for slaving the functioning of a tire in a given configuration so that a given friction coefficient is maintained.