The demand for more energy efficient vehicles is driven by environmental considerations and alternative engine technology. In order to reduce fuel consumption on future vehicles the power needed to propel the car has to be lowered. Hence, considerable efforts are needed to improve the aerodynamics. For a modern vehicle the potential for further improvements on drag is mainly to be found in the underbody region, Howell (1991). This requires more knowledge of the underbody flow and the flow around the wheels.In the present work the flow in the underbody region has been studied using a combination of experiments and calculations to obtain a more comprehensive database.The model chosen for this work was the so called ASMO model from Daimler Benz, which is a well known geometry that is available for the public on the internet. A simple model was preferred since the goal was to study the basic mechanisms behind drag generated by the underbody flow.The aerodynamics of this model was studied by analyzing how forces, pressure distributions and velocity fields varied for different configurations with and without wheel segments. The analysis shows that a major contribution to the overall drag on this model originates from the rear wheel segments.