A theoretical of the effect of different stiffness on body acceleration, suspension working space and dynamic tyre load for a passive system is made. Experimental results from a quarter vehicle test rig fitted with a passive suspension system are obtained. A description of road roughness is given and the effect of power spectral density slope is studied. The importance of using the correct value of slope of the road roughness in the calculations is also shown.

A theoretical model of the passive suspension system is made and calculated results are compared with those obtained experimentally from the rig. The mathematical model produces optimistic results for a passive suspension in comparison with experimental results. The best ride comfort is obtained in this work at the expense of the suspension working space. Active elements are needed to improve further the performance criteria within the allowable workspace.