It’s not called a spoiler for noth­ing!

Motor Equipment News - - DIESEL PARTS & SERVICES -

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.

READER RE­PLY 01506032

This Lam­borgh­ini Ve­neno spoiler has three fac­tory-set ad­just­ment points. Pic­ture Wikipedia/ Clé­ment Bucco-Lechat.

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