The current paper studies the dynamic behaviour of a coil spring in a vehicle suspension system. A portion of the coil spring is contacted with the top and bottom spring pads. The contact interface is modelled as a set of linear spring elements on the contact nodes of the coil spring. The eigensensitivity analysis is conducted to investigate the frequency variation of the stiffness-coupled system with respect to the contact stiffness variation. In the forced vibration analysis, the transfer function through the coil spring is obtained. The contribution of the coil spring modes to the load transfer is calculated by the modal contribution factor. It is shown that some of the longitudinal and bending vibration modes participate on the load transfer.