What Is a Car Spoiler?

Loud exhausts, big tires and lowered suspension might be showy, but one of the most noticeable components of any performance car is the spoiler. While it may seem like spoilers are all for show, on many vehicles spoilers are also a key part of helping a vehicle stay planted to the ground.

So, what is a spoiler on a car and how does it work? Let’s dive in.

What is a spoiler on a car?

A spoiler is an aerodynamic component that is designed to alter the airflow on a vehicle in order to achieve higher levels of cornering performance and high-speed stability.

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Every vehicle on the road is aerodynamically designed to move down the road and slip through the air with as little resistance as possible. The more slippery a car is, the less energy it takes to move it down the road. This wind-resistance measurement is known as drag. Fuel-efficient vehicles like hybrids and all-electric vehicles are specifically designed with low drag to make them go as far as possible on a charge, gallon of gasoline, etc. On the flip side, vehicles like trucks or tall SUVs are more prone to wind resistance and therefore create more drag.

Spoilers reduce drag in specific ways that benefit performance.

How do spoilers work?

To really understand how a spoiler works, we need to take a look at basic aerodynamics, specifically Bernoulli’s principle.

This principle states that air moves over a surface that is curved on top and flat on the bottom (like a car or an airplane wing), low pressure builds on top while high pressure builds underneath. On an airplane, this creates lift which allows planes to fly. Cars also experience lift but to a much lesser extent. As air moves over a vehicle, the low-pressure zone becomes most turbulent at the rear of the vehicle when the air no longer has a surface to flow over.

A spoiler is called a spoiler because it “spoils” the low-pressure airflow pattern around a vehicle as it speeds down the road. Rather than flow directly over, to the side, or under a vehicle, spoilers redirect the air to reduce turbulent low-pressure zones around the spoiler. This makes the air rushing over the car more effective at pushing the vehicle down, and that force pushes the vehicle to the road. It’s almost like putting a stack of weights on your vehicle.

Some spoilers can increase cornering performance because the force of the air flowing over the spoiler pushes the vehicle’s tires into the road and increases grip. At high speeds, many spoilers can provide stability by pushing the tires into the road with more force. Spoilers may reduce overall top speed, but most high-performance vehicles trade off speed for increased grip.

Types of spoilers and aerodynamic devices

Although the most well-known aerodynamic device is the rear spoiler, there are many aerodynamic components that work together to increase the performance of a vehicle.

Rear spoiler

A rear spoiler sits on the very back of a vehicle and is usually bolted to the trunk or integrated into the design of the trunk or hatchback. This not only looks great but increases grip at the back of a vehicle as described above. There are different types of rear spoilers, such as lip spoilers, along with spoilers that deploy at specific speeds.

Spoiler vs. wing

The terms “spoilers” and “wings” are often used interchangeably, but they are not the same thing. Spoilers disrupt existing airflow to create some downforce on the surface of the car, while wings are designed to create downforce on the surface of the wing. Race cars use what is essentially an upside-down airplane wing that creates high pressure on its surface and forces the entire vehicle to the ground with great force. For example, Porsche’s ultra high-performance 992 911 GT3 RS produces a staggering 900 pounds of downforce from its adjustable rear wing.

Side skirts

Side skirts direct air from the sides and underneath to the top of the vehicle. This has the effect of reducing lift and increasing high pressure on top of the vehicle.

Front spoiler

High pressure builds at the front of a vehicle as it increases its speed and front spoilers help direct this high-pressure air over the front bumper and up over the top of the car for more effective downforce.

Front splitter

Front splitters function like a wing on the back of a car, and they are designed to create downforce at the front of the vehicle. Super high-performance vehicles often use a combination of front splitters, rear wings, and aggressive side skirts to control the flow of air over the vehicle.

Vortex generator

Air moving closest to the surface of a vehicle moves slower than the air directly above it. This difference in speed is known as a boundary layer, and it’s undesirable for aerodynamic purposes because it causes friction. Vortex generators are small fins that are designed to “energize” the air closest to the surface of the car. This causes the boundary layer to be less dramatic and makes the car more aerodynamic by reducing air friction.

Air diffusers

Air flowing under a vehicle does so at low pressure. Diffusers at the rear of a car function as an expansion chamber and significantly slow down air as it exits the rear of the car, which increases the air pressure quickly. This difference between the low pressure created by the diffusers and high pressure toward the front acts like a vacuum and sucks the vehicle to the road.

Should you add a spoiler to your car?

First off, spoilers look great and offer a sense of style and substance to your vehicle. For that reason alone they can be worth the investment.

If you’re looking for performance gain, be cautious because most bolt-on spoilers offer few aerodynamic advantages. That being said, there are kits out there that offer more comprehensive performance benefits. These kits are usually installed by professionals and are designed to work with a specific model of vehicle and can provide some serious downforce potential. Unlike a bolt-on spoiler, which is merely for looks, these kits are properly engineered and expensive.

Spoiler pros and cons

If you’re on the fence about whether to add a spoiler, weigh the following against your individual situation:

Spoiler pros

• Improved handling and grip at high speed
• May help improve fuel economy
• Many enthusiasts think they look cool

Spoiler cons

• Usually costly if effective, but typically ineffective if affordable
• Can actually decrease topline speed
• Marginal impact at typical daily driving speeds
• May actually worsen performance if not designed for your vehicle

Conclusion

Properly engineered spoilers offer automotive enthusiasts an aerodynamic component that looks good and can increase the performance of their beloved rides. Although the physics can be complicated, well-made spoilers and aero kits are meticulously designed by engineers to help vehicles achieve a higher level of performance.