This study analyzes the effect of soil deformation on ride dynamics of off-road vehicles using a quarter-vehicle model integrating different equivalent soil stiffness models. Soil deformation has an effect on the tire sinkage, wheels contact area and the wheels dynamic interaction with the terrain, which affects the overall ride dynamics of the vehicle. Apart from the very simplified equivalent soil stiffness model documented in the literature, a new equivalent soil stiffness model is developed in this study, which encompasses the effect of soil deformability on tire-soil contact area. Two measured ground roughness profiles are then used for vehicle ride dynamics simulation. The analytical and simulation results analyses demonstrated that the variations in tire-soil contact area due to soil deformability and tire sinkage should be modeled for ride dynamics analyses, and soil deformability tends to reduce the vehicle body bounce acceleration and dynamic tire-soil interacting force with a compromise on suspension travel. Parametric studies further demonstrated the potential of optimal tire/suspension settings.