As it is known, the parameters of a heavy motor vehicle, including the frame, are not known in the initial design phase of the vehicle. Therefore, in this paper, an attempt is made to define the necessary dimensions based on the minimization of its lateral vibrations, while simultaneously minimizing the mass and maximizing the moment of inertia of the cross-section of the frame. Attention is given to the choice of the objective function in the optimization process, with a special focus on the interrelation of sub-objectives. The author's previously developed frame model and „stochastic parametric optimization” based on the Hooke-Jeeves method were used for the research. The calculated value of the unknown frame parameter is intended to serve for the final selection of the frame structure in the later design phase.