The geometric shape of the tires can have a large influence on the aerodynamic drag of a passenger car as it has been shown already in different publications like for example [1, 2, 3]. However, to optimize the shape of a tire, nowadays quite some effort is needed in terms of wind tunnel time and costs for prototype tires. In this paper an approach to optimize the tire's shape in model scale is described, which can help to reduce both development time and costs.The first step in the development of this method was to verify that the aerodynamic effects of the tire geometry in model scale are comparable to full scale tests. This was achieved by measuring different production tires in full scale and also by measuring the quarter scale version of the same tires. The only difference between the original and the model scale tires was that the scaled tires were not deformable. The results show that the difference between two sets of tires is comparable in full scale and in quarter scale.After validating this approach, several model scale tires with different geometries were manufactured and their influences on the aerodynamic forces were investigated. The results show that the aerodynamic efficiency of the tire can often be improved, when the outward shoulder of the tires on the front axle is smoothed. With only minor changes on a production tire, the aerodynamic drag of a vehicle can vary by more than ΔcD = 0.009.