It’s not called a spoiler for nothing!
One of the least effective “go-faster” bits you can get for your car is a rear spoiler. Yes, that’s right – LEAST effective. What’s more, it can actually make your car handle worse and lead to you running off the road!
Just fitting on a spoiler isn’t necessarily going to do anything for your car – except (arguably) to improve its looks – as most of them don’t have any effect on the car, except maybe increasing the drag co-efficient, until you’ve exceeded our national speed limit of 100km/h.
So that means that unless you’re prepared to exceed the speed limit, or go racing on a track, the vast majority of spoilers out there don’t do anything. You don’t get any bang for your buck!
At the same time it must be remembered that they have to be fitted properly, and in the right place – and they have to be sturdy enough to withstand the forces air pressure is going to put on them – otherwise they can do mort harm than good.
Spoilers are supposed to spoil aerodynamic lift, the force that wants to pull your car off the ground. They’re supposed to push your car onto the road.
In fact they work the opposite way to an aircraft wing. Whereas an aircraft wing is designed to give the craft lift, to make it fly, a spoiler is designed to stop the car from flying..
Spoilers deflect air upward, which creates a downward force on the car. This in turn pushes the tyres more firmly onto the road, resulting in better grip and hopefully enhanced roadholding.
At the same time a properly designed – and positioned – spoiler can reduce the effects of aerodynamic drag and air resistance. And the less air resistance your car has, the less fuel you’ll have to burn. But, again, it won’t start to take effect until you get to higher speeds.
Having said that, here comes the downside. A spoiler only works if it’s cutting through the air at the correct angle, and if it’s installed on exactly the right place on the car.
Putting it in the wrong place, or at the wrong angle, can create too much downforce at the rear of the car, effectively counter-acting the grip of the front tyres and making the car understeer in corners.
Experts say finding the right setting requires at least three hours in a wind tunnel.
Factory-installed spoilers on higher-end sports cars are very effective, but many others out there probably aren’t so effective – and some car manufacturers even say their spoilers are for looks only.
If you don’t have access to a wind tunnel there is a way you can test the effectiveness or otherwise of your spoiler, but it takes a lot of repetitive work.
What you have to do is accelerate to a high speed on a quiet stretch of road, then put the car in neutral and see how long it takes you to come to a stop. Do this in both directions.
You should do this before and after fitting the spoiler, and if it’s adjustable, before and after making any changes.
If the spoiler shortens your slowdown time, it’s increasing the drag; if it lengthens the time, it’s improving the aerodynamics.
Having said all that, remember there’s not much effect at less than 100km/h, so the differences are going to be very small.
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This Lamborghini Veneno spoiler has three factory-set adjustment points. Picture Wikipedia/ Clément Bucco-Lechat.