Here is a question I have been asked and I don't really know the answer to it:
What effect does the rear spoiler have on handling?

We see lots of different types of rear spoiler on another thread. Do any of these effect handing, and if so, which ones?

 

At speeds under 100 mph, I doubt they have much effect other than cosmetic.

 

I'd say zero meaningful effect below 100.

 

I'm wondering about higher speeds. I'm wondering if there are any wind tunnel results that analyze this.

 

I really don't know the correct answer to the question but as the others have said I can't imagine on the street at anywhere near legal speeds we could see a difference.
With that said I do remember the Greenwood wing attaches through the rear deck onto the frame. I believe this was the only wing that was mounted that way. The reason for that was any down force the wing generated would be applied to the chassis not the body work. So there must be some benefit at high speed. Either that or it was just good marketing.

 

Honestly almost all rear spoilers on cars are a safety measure for the bozos that venture into speeds over 130mph ()

It's not what you are thinking where the spoiler is going to give you an edge over the guy without one performance wise. While this may be true for serious pro racing applications, for the rest of us its to make sure we don't create lift on the rear end at very high speeds which generally happens on all cars. Thus the name spoiler, it spoils the airflow and prevents the air from creating a low pressure zone over the rear end while there is a high pressure zone under the car. This is the basic concept of an aircraft wing and its no good when you're essentially driving a wingless fuselage.

It would be a bad idea to release a car capable of doing 150mph when the chance of survival for the average joe is slim to none. Its keeps the rear planted so if you are flying by at 130-140 and must shift a little to the left of right to avoid something or follow the curvature of the road you stay alive. The best way to put it is it increases the margin of error at high speeds. How much? who knows.

 

Factory lip & wing spoilers are for the most part cosmetic.
Vane spoilers are the most effective. Vane angle & height varies the effect. If class rules dictate a height/angle restriction a wicker blade can be added for increased effect.

 

Everything that I have read in the past indicated that the wing or spoiler was strictly cosmetic at speeds less than 140 MPH. At 140+ they started to apply downward force to keep the rear end planted.

 

I drove a friends z06that has a wing on it and it makes a diff at much lower speeds than what is being discussed here. So are we talking about just the greenwood style? We all as kids have put our hands out the window and played with up and downforce going much slower and could feel the power so imagine a large wing and the force it produces.

 

This is a good point......WW

 

A large WING, yes. OP asked about a "spoiler" which to me is a lip on the rear. Obviously, if you flip an airplan wing upside down and stick in on the back of a car (in clean air), it's going to produce massive down force. So the answer to the question is;

*Depends on the "Spoiler"
*Depends on the Speed

Must "spoilers" that people buy for their cars or that come on cars, stock are for looks only and don't generate any meaningful down force in typical driving.

 

you know, ....GM designed the C4 to go 160mph in its stock form. And then noted that is also its stock top speed. And there is nothing on the rear deck but the fuel cover.

So I would tend to agree with those who state there is not an effect except for cosmetic purposes.

That said, without wind tunnel testing and documented stats, who is to say what a larger wing/spoiler is capable of doing? Does it matter?, probably not to most of us.

I've driven mine at near top speed at Talladega and I can't say that I was missing anything because it doesn't have a rear spoiler. It hunkered down and tracked just fine.

 

It is ALL about the shape of the car. The corvettes shape makes the spoiler pretty useless at low speeds. However, car with a very rounded back end, especially Porsche, create a vortex at the tail end at speeds just over 50mph! This vortex becomes dangerous to the stability of the car at just 85mph. Porsche discovered this flaw and you will notice they all have wings/spoilers. The older ones have fixed ones, the newer ones actually have spoilers that automatically rise up from the rear at speeds over 70mph. Of course this is adjustable and some guys have it pop up around 55mph but I believe they come up at 70mph from the manufacturer. They are not pretty IMO especially the Boxter, its just a flat lip that sits perpendicular to the car. So in their application, spoilers are purely functional.

 

The opinions expressed on this thread seem to cover the entire spectrum. The last two posts illustrate that quite well. I am hoping that someone has wind tunnel data that can settle the question.

Again, there are different types of spoilers and wings. Which, if any, help with handling at speed? I have seen first hand that at speeds in excess of 130, handling and stability are extremely important.

Thanks to all who have contributed to this discussion. I am enjoying the responses and points of view. Each one makes a good point.

 

What you're looking for is a little ridiculous -way too vague...which is why answers have covered the entire spectrum. No one is going to have any wind tunnel data.
*First, I doubt that anyone here has a wind tunnel. I know that I don't.
*Second, WHICH "SPOILER" do you want data on? I'd suggest going to the manufacturer's web site and seeing if they have data available.
*Third, At what speed? and
*Forth, on what car? Mounted how high? Where you place the wing/spoiler has as much an effect as the wing/spoiler itself.

You question is like asking "How fast will a modified sports car go?"

Getting it back in context, you said;
and I said;Most if not all of the spoilers that you saw in another thread, are for looks and don't provide any meaningful function in most driving.

 

The Sledgehammer went 254 without a wing. It does have a lip.

 

LOL I am hoping someone knows about existing wind tunnel data. I find that some people on this web site have access to very interesting knowledge. I certainly don't think anyone has their own wind tunnel.

"At speed" is a phrase sometimes used on this web site to indicate high speeds, and is left vague because that is supposed to be understood.

What car? A C4 obviously.
How high? depends on the spoiler/wing design. Obviously they all go on the back end of the car.

Your opinion is noted. Not everyone has agreed to it. I would like some data to back up that opinion. You earlier said "zero effect at speeds below 100", and yet there is a post on this thread that questions that. It sounds like you are shooting from the hip and are frustrated that we don't take your "guess" as the last word.

I just think the topic is interesting and I am hoping get some data on the subject. If anyone knows of wind tunnel data I would be very interested in getting that information.

The Bugatti Veyron is designed utilizing some aircraft engineering because of the great speeds it can travel at. I'm sure some of those effects come into play at much slower speeds, such as the need for a wing spoiler on the Porsche. The C4 Corvette has different wind tunnel attributes than a Porsche and the comment about the Sledgehammer was quite interesting to note, and shows a major difference between C4 Vettes and Porsches.

I am enjoying this discussion. I'm sorry that not everyone is.

 

 

Fair enough. Trying to help, but I can see you aren't listening. Let me know when you find that "precise" amount of down force that those spoilers "on another thread" provide.

 

Most of the "spoilers" found on the street have as much effect on aero, as the tennis ***** help with shock absorption...