Abstract
In this paper the suspension ratio is defined as the ratio between the force acting on Spring --Shock Absorber Group (SSAG) and the force on the contact road -wheel. Some drafts show the utility of this ratio for the engineering calculation of the stresses on SSAG under several load conditions. Besides a method is presented to calculate the forces in a suspension system that is used for some competition vehicle. It is very simple to use and, with the necessary modifications, can be also used to calculate the actions on the suspension elements under steering. In alternative the suspension ratio is defined as a vector having three different components with regard to co-ordinate axes. This definition is more useful for the engineers because it permits the evaluation of the loads on SSAG also in presence of adhesion forces and a more exact result in frequency analysis calculation modifying elastic and damping constant.