A system is presented for controlling the stability of a vehicle. The system includes a controller using a slip parameter G_OPT corresponding to a predetermined value of the coefficient of friction or a controller maintaining the functioning of the tire at an optimal value ^OPT of the drift angle corresponding to the maximum value of the draft thrust F_target. The controller performs the following operations (where X is either the slip G or the drift angle , and Y is either or F). Estimations or measurements are determined for at least one pair of values (X_i, Y_i). The corresponding values of the slope _i are determined for the straight line passing through the origin (X_i, Y_i). Coefficients A_p are calculated by direct calculation or by a regression from a sufficient number of pairs with (_i, X_i) so as to model a variation curve _i=f(X_i, A_p). A target value X^Target is calculated by using a predetermined invariant "Invt".