The ubiquitous spoiler is the little flap or raised protrusion on the rear decklids

of coupes and sedans, or on the upper edge of the rear gate on hatchbacks.

Although the spoiler is often a cosmetic upgrade designed to tell the world that

your car is “sporty,” it also has a very specific role in aerodynamics.

Whether a spoiler is needed on your car is matter of

-

 How you use your car

-

 How your car was designed

As the name implies, this device spoils the airflow over the top half of the car

at the trailing edge of the car’s upper surface. The spoiler can keep airflow

from tumbling and creating a swirling vortex behind the car. This is important

for a couple of reasons — without a spoiler, swirling air behind the car can

create both

-

 Drag (which can keep the car from moving forward as quickly as possi-

ble). Drag is expressed as a numeric coefficient of wind resistance.

-

 Lift (which reduces the car’s grip on the road at speed)

Manufacturers have been known to add spoilers to cars that didn’t have

them in the original design. The Audi TT was released first without any

spoiler. It could only be purchased with a spoiler after reports began deriding

its high-speed stability and inherent rear lift.

Wings

A wing on a car is an upside-down version of the wing on an airplane. Instead

of lifting, the upside-down wing pushes the car against the ground.

Because the wing must catch an undisturbed flow of air, most wings are

mounted on raised pedestals, as shown in Figure 8-1.

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