A procedure of the spindle displacement back-calculation to acquire body loading spectrum is presented through a case study of a light-duty bus.First,road loads in the proving ground is collected by arranging some transducers.Then,the multi-body dynamic simulation model with a satisfactory accuracy is established.Finally,based on the above two factors,virtual iteration is applied to cascade body loads from the wheel hubs.The conclusion can be drawn that the simulation signals obtained from the proposed method agree well with the experimental data,and thus the load information extracted from the body interface points can be utilized to evaluate the fatigue lifetime.