1. A vehicle stability control system in which a characteristic parameter Q of a functioning of a tire of the vehicle intended to roll on the ground varies as a function of a parameter P according to a certain law, an optimum value of the parameter P being imposed by a controller directly or indirectly, so as to act on at least one of elements chosen from a group comprising a rotation torque applied to the tire, a steering angle of the tire, a camber angle of the tire and a vertical force applied to the tire, in which the controller comprises means for: determining estimations or measurements (P i , Q i ) for “i” successive levels of values; using, in parallel, “n” calculation algorithms, each determining a target value for the parameter P, to obtain a target value P Cn for each algorithm, selecting as the optimum value of the parameter P the best of the target values P Cn by subjecting the “n” target values P Cn to comparisons aimed at eliminating the least likely target values.