This paper illustrates a possible approach to evaluate the influence of the bushing stiffness on the suspension elastokinematic performance. Particularly when a multilink suspension is investigated, the contribution of a single bushing stiffness on the whole suspension assembly performance is not immediately obvious. For this reason a standard sensitivity analysis approach could require a high number of simulation runs to describe, for a given geometry, the relationship between bushing stiffness and suspension performance.
Starting from a basic analysis a design methodology has been created with the aim of supplying the suspension engineer with an effective and rapid tool to address this class of problems.
For a fixed geometry the concept of geometric sensitivity is introduced as complementary to the elastic sensitivity. In this way it is possible to distinguish the influence due to both the position and the orientation of the bushing with respect to the influence of the assigned bushing stiffness itself. The sensitivity is evaluated as an intrinsic value, independent from the values assigned to the whole assembly bushings when the sensitivity analysis is run.
Finally, as an example of the methodology, the design guide-line followed for the tuning of the bushing stiffness of a multilink rear axle (the new Lancia Thesis) is presented.