Reducing drag is also a factor in sports car design, where fuel efficiency is less of a factor, but where low drag helps a car achieve a high top speed. However, there are other important aspects of aerodynamics that affect cars designed for high speed, including racing cars. Notably, it is important to minimize lift, hence increasing downforce, to avoid the car becoming airborne.
Increasing the downforce pushes the car down onto the race track—allowing higher cornering speed. It is also important to maximize aerodynamic stability: some racing cars have tested well at particular "attack angles", yet performed catastrophically, i.e. flipping over, when hitting a bump or experiencing turbulence from other vehicles (most notably the Mercedes-Benz CLR). For best cornering and racing performance, as required in Formula One cars, downforce and stability are crucial and these cars must attempt to maximize downforce and maintain stability while attempting to minimize the overall Cd value.
The average modern automobile achieves a drag coefficient of between 0.30 and 0.35. SUVs, with their typically boxy shapes and larger frontal area, typically achieve a Cd of 0.35–0.45. A very gently inclined windshield gives a lower drag coefficient but has safety disadvantages, including reduced driver visibility. Certain cars can achieve figures of 0.25–0.30, although sometimes designers deliberately increase drag to reduce lift.
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