Spoilers, speed and staying stuck to the ground
My two-year-old has recently learned the word “spoiler,” which he’s pretty sure is the key to identifying race cars. Every car he sees, from punky Mazdas to custom Mustangs are excitedly called out as race cars, simply because they have the slightest indication of an air foil on their trunk. This isn’t really by accident— most cars you see on the street with a spoiler probably have it for the sake of aesthetics rather than handling. While some cars absolutely depend on these aerodynamic enhancements, a badly designed spoiler can actually make a car less of a racer, increasing drag without any benefit beyond impressing my son.
Like flying, upside-down
A properly installed spoiler (or more specifically, rear wing) should act like an upside-down airplane wing. When air goes around a wing, the air underneath pushes the wing upwards into the sky. On a car, the shape, and thus the lift, is flipped so that the car is pushed down onto the road. This downward pressure, called downforce, increases the cars grip on the road. That extra grip gives the driver better control, especially when cornering, making maneuvering at higher speeds possible. Without a spoiler, the only other options to increase the cars grip would be to increase the car’s weight or quality of the tires, both of which may cost the car some potential speed. So clearly a spoiler is the way to go (faster).
Spoiling the fun
Unless your car’s spoiler isn’t actually designed and installed correctly. At a certain point, a spoiler is capable of generating so much downforce it makes more air resistance, or drag, it slows the car down enough to be a detriment to performance. Top race cars, like a Formula 1 racer, carefully tune their lift/drag ratio making use of tools like wind tunnels to ensure things are running as optimally as possible.
All of this is only relevant if you’re driving fast though. Just like an airplane taking off, a spoiler needs a sufficient amount of air moving over and under it to produce a relevant amount of downforce. The minimum speed most drivers will notice anything is around 62 mph. In some cases, cars have been built with dynamic spoilers, which adjust themselves according to your speed and handling needs. So despite the wishes of my two-year-old, our stop-and-go driving makes it hard to justify getting a whale tail for our Mazda 5 any time soon. Maybe some racing stripes though.
Source: What exactly is the purpose of the spoiler on a car and how does it work? by Frank DiBonaventuro, PhysLink.com
