Modern cars are more aerodynamic than ever before, in the sense that most have much less drag when driven at highway speeds to help boost fuel economy. But even the slipperiest cars can be scary to drive when the speeds are ramped up, because the front or rear ends of the car can lift and make the car difficult to control. That’s why when production cars are adapted for the racetrack they usually have modifications like air dams, side skirts, and spoilers.

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The aim of such additions is to overcome design problems that only reveal themselves at high speeds. They’re generally devised to provide downforce and counteract the vehicle’s tendency to lift, so the tires stay firmly in contact with the road surface for traction, braking and steering control. Such modifications can often increase drag, but the goal of the car builder is to achieve a balance between the necessary downforce and the minimal amount of drag.

The effectiveness of the spoiler is dependent on its size, angle and the shape of the car. If its primary function is to provide downforce, it will be angled more vertically so the high speed airflow coming off the roof toward the back of the vehicle is disrupted, reducing its velocity and creating high pressure. However, spoilers can also be designed to reduce drag. On some cars the distance between the rear edge of the roof and the tail end disrupts the airflow and increases drag. A properly designed spoiler can, in effect, lengthen the distance or make the slope gentler, preventing airflow separation and reducing drag.

Regardless of where a rear spoiler is mounted on a street-driven car, it won’t affect handling much when the vehicle is at legal highway speeds. Spoilers are firmly rooted in racetrack performance, but in the realm of public roadways they’re much more for show than go. On a sedan, a roof spoiler can provide an unexpected styling element, one that catches the eye as it scans the vehicle’s roofline, creating visual interest in the overall design. Roof spoilers can often be more pronounced on a hatchback. A properly designed spoiler can improve airflow over the vehicle and create an aggressive, performance look.

Along with a large selection of styles, our roof spoilers also come in the most popular aftermarket body accessory materials including lightweight, affordable fiberglass; tough, durable ABS plastic; flexible urethane; and high-tech carbon fiber. Most install quickly and easily with strong 3M adhesive. You can order your spoiler unpainted, but we strongly urge you to choose the painted option. A local body shop won’t be able to paint the spoiler for less than the price difference, and your spoiler will arrive at your door color-matched to your vehicle and ready to install.

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Guides & Articles

  • Spoilers
    What Kind of Spoiler is Right for You?
    The function of a rear spoiler is to control the flow of air streaming over a vehicle and properly manage it when it reaches the rear where turbulence is most likely to form. A correctly designed spoiler will counteract the lifting forces that most cars experience when speeds get high, and it will enhance rear grip by keeping a vehicle's rear end planted firmly against the road - without causing excess drag.

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11 STI
Color matches perfectly, install was exceptionally easy.
BPosted by Bryan (Norfolk, VA) /
2008 Subaru Impreza
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