In recent years, aerodynamic analysis of automobileshas became one of the most important issue which affect thecompetition of the companies present in the world markets.Therefore it can be considered as one of the most importantfactor in aerodynamic design of the vehicles. This paperinvestigates the effect of aerodynamic devices on how to reducethe aerodynamic forces in the rear of a car model. The studywas conducted experimentally at speeds of 0 to 60 m/s and aconstant speed of 60 m/s. In these experiments aerodynamicforces, lift and drag coefficients were measured and the effect ofthe spoiler with three different heights along with diffuser werecompared. The most important result of these experiments wasthe effective reduction of lift and drag coefficients with thepresence of a spoiler and diffuser on the model.