In real mechanical situations it is a certainty there will be non-linear behaviour present at a range of frequencies and amplitudes. It is not, however, always possible to have a priori knowledge of the input to a system. A method has been developed by Adams to allow the experimental engineer to overcome such problems. The technique is addressed in this paper and applied to both simulated and experimental data. The method makes use of time domain characterisation via work and characteristic diagrams and also the frequency domain approach toward non-linear identification from feedback of the outputs, (NIFO). This paper attempts to use these time and frequency domain techniques to locate, characterise and quantify non-linear behaviour using both simulated and experimental data. The approach to this work is to obtain simulated data from a quarter car model and real data taken from an experimental rig. The data will be taken at a variety of frequencies and amplitudes and the above time and frequency domain techniques will be applied.