The aerodynamic development of a race car often includes wind tunnel testing and track testing. Wind tunnel data includes aero forces and moments which are measured by the wind tunnel balance. Track data is usually derived from stop watch and driver “feel.” The instrumentation that provides a correlation between wind tunnel and track data is pressure ports. Pressure port data helps the test engineer understand the reason why a body modification causes a change in the balance data. This paper presents typical pressure port data measured at the wind tunnel and describes the effects that deck spoilers, yaw, and traffic interference have on balance data and body pressures.