The analysis are carried for two reasons:

1) Check (negative) lift: As vehicles now travel at high speeds, their bodies are subjected to aerodynamic forces. If the design is not considerate, increasing the speed of the may topple it over. Ergo, it is essential to generate lift in the negative direction to maintain the normal contact force of the vehicle.

2) Minimize drag: Increasing drag means more load on the engine, which greatly affects the fuel-efficiency of the vehicle. It also reduces top-speeds.