What’s the Point and Purpose of a Rear Spoiler on a Vehicle?

February 5th, 2020 by

Toyota Supra coupe exterior side shot with gray metallic paint color and rear spoiler attachment

Spoilers are one of the most common accessories on not only sports cars, but sedans and roadsters, and even compact spoilers can now be found on the back edges of some hatchback and SUV roofs. So, what do spoilers do, and how do they work?

First, let’s define a few things and give some background on the topic.

Aerodynamics and Car Efficiency

Basically, aerodynamics is the study of how air flows around a certain object and is especially applicable when that object is in motion. Designing vehicles requires an understanding of aerodynamics to create better flow and to reduce drag. The better a design for aerodynamics, the better fuel efficiency a model will have, before taking engine power and mechanics into account.

Engine Power, Fuel Consumption, and Wind Resistance

After your vehicle reaches a certain speed, your engine power is mostly battling wind resistance. In fact, at that point, roughly 80% of power is used to prevent natural forces from slowing down your car rather than speeding up. Within that equation, more wind resistance and drag mean more power and fuel usage.

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So, what does all of this half to do with a Rear Spoiler accessory? Let us explain. 

#SpoilerAlert: How Spoilers (and Wings and Side Skirts) Work

A rear spoiler is one of the most common aerodynamic accessories used to disrupt the flow of air. Its design ‘spoils’ the smooth flow of air at the back of a vehicle to disrupt and prevent lift. 

Lift is an effect created by airflow when it goes under your vehicle. The trapped air tries to raise your vehicle, reducing grip on the road. 

By preventing or greatly reducing lift, a spoiler improves airflow and therefore vehicle performance and efficiency by some small measure. 

2020 Toyota GR Supra 3.0 Premium exterior shot with yellow paint color following another red GR Supra model
Volkswagen I.D R Pikes Peak concept electric racing car exterior rear shot of bumper and spoiler with highway sun flare

Essentially, all other aerodynamic accessories (Front Spoilers, Front Splitter Rear Wings, Side Skirts, Vortex Generator) aim to disrupt airflow in a similar manner, by minimizing air from getting trapped under a vehicle and other ‘dead spots’, preventing lift, and therefore improving airflow.  

Meanwhile, an Air Diffuser tries to disrupt air that does get trapped under a vehicle, rather than preventing its entrance. 

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