Do spoilers on commuter cars actually make any significant difference?



I understand the aerodynamic principles that make spoilers important for performance cars (at least in broad strokes), but I have always wondered if they actually make a big difference in cars that are not so performance oriented, especially fwd commuter cars. I know that aero is less effective at slow speeds, so I would also like to know at what speeds spoilers really give an advantage?
Thanks in advance for sharing your knowledge!

In: Engineering

Much higher speed than standard commuter cars. Honestly, mostly I suspect they actually worsen performance at lower speed by adding weight and drag.

On regular cars, the spoilers are mostly a cosmetic visual thing. They must have a specific shape to create aerodynamic forces, and lot’s of them don’t. But I’m sure there are some that actually do the job.

Other than that, many regular cars with spoilers are front wheel drive, where a spoiler on the rear end is less useful (they are most useful for RWD cars to prevent the tires slipping during aggressive cornering, and on FWD, the rear wheels are less likely to slip since they are not driven and can spin freely as they need)

Spoilers provide downforce at highway speeds. The downforce helps the car stick to the ground, especially in turns. How much depends on many factors. Indy cars provide enough downforce that at race speeds they could literally drive on the roof of a tunnel. On small commuter cars the downforce is still there and helps at highway speeds. But overall the total performance of the car suffers, albeit an imperceptible amount. This is because it adds more drag to the vehicle. More drag equals less gas mileage and performance. And for you speed junkies out there. A big spoiler on a fwd car will most definitely slow you in the quarter mile, and in extreme cases can cause your front wheels to loose grip under high acceleration/high speed situations. The back end of the car is being pushed down which pushes the front end up. This is because these cars were not designed for this. High performance cars have other aero components to put downforce in the front as well.

Spoilers on commuters cars have an entirely different reason than racecars.

They dont exist to create downforce, they exist to spoil areas of low pressure that cause drag.

When the flow is smooth this is usually a good thing. This is called “laminar flow”. But on the back of the car the smooth flow causes low pressure as the air goes over the back edge of the vehicle. The spoiler is there to ruin this airflow and reduce the low pressure causing drag on the tail.

Thats why the spoilers are shaped differently on commuter cars.

They’re cosmetic. A spoiler that operated at normal car speeds would be comically huge.

Then there’s also the fact that a spoiler would be adding downforce to the rear wheels when most cars are front wheel drive.

There seems to be some confusion in the responses between a wing and a spoiler. A wing, like F1 cars have, is basically an upside down airplane wing, that pushes the car into the ground. At legal highway speeds, a wing has little to no effect.

A spoiler is different however. It is used to break up airflow. They are very useful for reducing drag and increasing fuel efficiency. Many cars will have a front spoiler to reduce the amount of air going under the car. Rear spoilers can reduce the low pressure behind the car. You will often see cars with rather flat rears have spoilers to make the rear of the car appear more sloped to the air.

Famously, the Audi TT was released without a spoiler. After a number of accidents, it was recalled and a spoiler was added:

When it comes to aftermarket spoilers, fins, and wings, the intended purposes may vary, but the practical results are the same. You see, many of these bolt-ons promise signifigant gains in a vehicle’s performance parameters that are often difficult, if even possible to measure. However, the unintended consequence of birth control is un. deniable.