Computational fluid dynamics is implemented to investigate the influence of the wheel contact patch on the global car aerodynamics. Two main aspects of the problem are the contact step and patch shape. Three important parameters: step height, cut angle, and tire tread shape are taken into consideration. For validations of the numerical results, the experimental data are also considered. The obtained results show that the step height may not significantly affect the global flow field. But when the cut angle increases, the flow separations on the two sides of the front wheel patch will be suppressed successively, which generates two critical points and a sudden drag decrease is achieved. Besides, tiny differences in tread shape can effectively change the flow rate of the underbody and make a huge drag discrepancy in the results. In conclusion, the cut angle and tire tread shape carefully must be dealt with in aerodynamic applications of automotive engineering.