To examine the effect of the minimum ground clearance h on the aerodynamic lift and velocity distributions, the time-averaged airflow around a mileage competition vehicle was simulated using the computational fluid dynamics. The speeds of the inlet airflow and the ground were both set to 30km/h based on the running conditions in the mileage competition. The rotation speed of the wheels was also included in the simulation. The minimum lift (with a maximum downforce) occurs at h=50 (mm) along with a minimum aerodynamic drag. A decrease in the lift (increase in the downforce) takes place as h decreases from 150mm to 50mm as the flow speed between the vehicle underbody and ground increases, thereby raising the downward curvature of the streamline. Whereas, an increase in the lift (as h decreases from 50mm to a very small clearance of 30mm) happens through a remarkable reinforcement of the downwash behind the vehicle, accompanied by a wide separated flow near the trailing edge. Furthermore, the occurrence of the minimum lift at h=50 (mm) was also confirmed by calculating the circulation at the spanwise center of the vehicle.