An analytical approach for design and performance evaluation of torsion beam rear suspension

Torsion beam rear suspension systems have been widely used in small passenger cars owing to their compactness, light weight, and cost efficiency. To study the roll behavior of torsion beam suspension systems, analytical equations to obtain roll center height, roll steer, and roll camber have been developed in terms of geometry points through the kinematic consideration of the system on the assumption of rigid body motion. In most cases, commercial software for finite element methods or experimental equations for individual parts are utilized for the design and evaluation of the suspension systems. This paper, however, proposes an analytical method to calculate the torsional stiffness of a torsion beam for various loading conditions based on the assumption that a torsion beam is in the range of linear torsional angles with a constant cross section. The proposed method is useful for exploring suspension system design, especially in the early stage of vehicle system development in which detail design parameters such as layout, cross sections, and materials are not yet determined. It is shown that the torsional stiffness and roll stiffness predicted using the proposed method has sufficient precision with around four percent difference from the results of finite element analysis and bench tests.