Many commercial vehicle manufacturers are now using computer simulation as an aid in assuring compliance with FMVSS 121. One particularly important aspect of such a simulation is the analysis of the interaxle load transfer during braking due to tandem axle dynamics.In this paper, two analyses of the four spring tandem suspension with short load leveler are presented. One, a simplified model, serves to illustrate the mechanism of interaxle load transfer and to identify the design parameters which affect this phenomenon. Improved accuracy is obtained by the second model through the inclusion of frictional forces that develop at the points where the leaf springs contact the frame. Comparison of effectiveness test data indicates good agreement between empirical and simulated results when this advanced suspension model is used in conjunction with existing commercial vehicle simulations.