Passive safety systems in vehicles, which are directly responsible for the optimal passenger protection in the case of an accident, are critical factors in contemporary vehicle development. Rollover maneuvers, e.g. rides over an embankment or a ramp, are considered to be especially hazardous, as they always involve a high risk of injury or even death and of vehicle damage. Today, for reasons of cost and development time, computer simulations play an important role in the development of such safety systems. For simulating the vehicle dynamics, the vehicle is realized as a complex multibody system, as a base for the mechanical part, and which is combined with additional non-mechanical components like hydraulics, sensors, driver and environment into an overall mechatronical system. This concept is realized within the threedimensional vehicle dynamic simulation environment FASIM C++. The central issue in this paper is the modeling of the vehicle ground contact, which may occur between the underbody and the ground during embankment and ramp maneuvers. Finally, the results from test drives for a cabriolet, which has been selected by the car manufacturer from simulations with FASIM C++, show a good coincidence between simulations and experiment.