Purpose <p>The hydraulic shock absorber is the crucial element of tracked vehicles suspension that is utilized for dissipating the transmitted energy from the road disturbances to vehicle hull. Most of shock absorbers have intrinsic nonlinear characteristics in order to compromise the ride comfort and terrain handling. Modelling of nonlinear behaviour of shock absorbers has been studied by many researchers to provide models that can be employed in simulation of vehicle suspension system. The aim of this study is to experimentally characterise the dynamic properties of shock absorber of a light weight tracked vehicle.</p> Methods <p>By performing comprehensive tests under different sinusoidal frequencies and amplitudes representing a wide range of operating conditions. These dynamic properties are modelled by a nonparametric technique based on the restoring force surface (RFS) approach and Chebyshev polynomial function.</p> Results <p>The results of this study indicate that the shock absorber possess highly nonlinear dynamic properties where it is relatively soft in compression and hard in rebound. The RFS constructed from the measured data has captured the shock absorber dynamics excellently. The validation data sets representing a wide range of excitations of the shock absorber show that the application of the RFS to predict the shock absorber force for known displacement and velocity is reasonably precise.</p> Conclusion <p>The nonparametric model provides an accurate representation of the shock absorbers nonlinear behaviour.</p>