Method of determining the behaviour of a shock absorber in the sprung mass system of a vehicle and a jig for performing the method

A jig for determining the behavior of a shock absorber arranged in a wheel suspension unit within the sprung mass system of a vehicle, comprising a wheel supporting plate, a body deformable under load on which the supporting plate is mounted, a bearing plate engaging the deformable body, means for applying vertical vibrations to the bearing plate, and means responsive to the deformation of the body, said deformation responsive means providing at least one electrical signal representing the magnitude value of the vertical contact force of the wheel on the wheel-supporting plate during the applied vertical vibrations, and determining means responsive to said deformation responsive means for indicating whether the magnitude value of the vertical contact force exceeds a predetermined magnitude value as an indication of the useability of the shock absorber.