I was driving around as I usually am, and I noticed an unusual amount of spoilers on cars that are not sports cars in your typical sense. Anyways, I was wondering, what do Spoilers do exactly? Do they only work on certain cars, and under certain conditions, and at what threshold do they obtain effectiveness?
I suspect there are already pages out there, Googling has not turned up much useful information however…
On any car you or I can afford, the purpose of a spoiler is to “look cool.”
Period.
The speeds necessary for one to actually have a measurable effect are illegal in every country but Germany. 
They usually cause me to snicker quietly to myself…
Not a good answer, I know.
Of course I don’t mean factory spoilers – they contribute to the look of certain cars. My first Bonneville had factory spoilers. The non-spoiler Bonny’s looked like big, smiling butts.
On street cars, they pretty much do practically nothing aside from appearance. They’re supposed to act like a wing that pushes down on the rear of the car to maintain traction. Coming Back to my Bonneville, well, it was a front-wheel-drive car.
Beats me.
Quite a bit of good information here from when I asked this question three and a half years ago.
I believe that a 95% of rear spoilers are there for purely aesthetic reasons.
Some cars, due to their body design, have stability issues in high speeds. Remember early Audi TTs? Their rear end design was creating aerodynamic lift, destabilising the car at high speeds. Later TTs have a little spoiler to counteract that lift.
Also there are front spoilers too. They add a downforce on the front wheels to enchance steering, but also focus incoming air into the car’s various coolers and the disk brakes.
Not true. Even radio-controlled cars can go fast enough to make aerodynamic performance significant. Certainly at highway speeds spoilers can have a measurable effect.
However, most spoilers are designed to look cool without disrupting, rather than enhancing, the aerodynamics of the vehicle.
I thought that only italy didn’t have a speed limit (on freeways) , what did the germany reference mean ?
According to Wikipedia “The German autobahns are famous for being the only important public roads in the world without blanket speed limits for cars and motorcycles, though traffic on them is usually heavy enough to restrict speeds to little above typical motorway speeds in most cases.”
A couple of weeks ago a tourist show on TV had a segment about Germany. The woman reporter was doing 140kph (88mph) in the slow lane and cars were just racing past her.
They seem like they’d be pretty useful if you wanted to transport something large and couldn’t shut your trunk. Just look the bungee cord around it and hook it onto itself.
My daughter reckons their ‘handles’ to drag the car with when it conks out.
I live in Germany, and brought my American car with me. Autobahns are fun. It is true that many large stretches of Autobahn have no speed limit. In high traffic areas, the speed limit is usually 130kph (81mph), with reductions between 80 and 120 depending on certain situations. In the speed-limit free zones, the right lane stays at a usual 100 kph, since semitrucks have a national speed limit of 100kph. The left lane is usually free, since Germans aren’t in it unless their passing, and has cars usually ranging in speed from 130 to 250 kph. I myself usually set the cruise in these sections at 90mph (about 145kph), but I’ve been known to break the 200kph barrier on occasion, but not often. Believe it or not, with all this (to our American minds) excessive speed, the Autobahns have a fatality rate per capita that is significantly lower than in America. Drivers are much safer, and have excellent lane courtesy. I feel considerably safer going 90mph on the Autobahn than I do going 70 on a US interstate.
When I first got my car over there, I was on a relatively empty stretch of A5 from Frankfurt to Mannheim, 3 lanes, and I was going 115 mph in the center lane…then a Volkswagen blew my doors off on the left. It was quite an experience. 
Jman
Taking a car to Germany is kinda “taking coals to Newcastle”, isn’t it?
Hmmm… it occurs to me that I’ve never used that expression in the States, so I don’t know if you’ll understand it.
If I understand it correctly, it’s like saying “taking something to a place known for producing that item.”
So it would be like “taking steel to Pittsburgh.”
That is pretty true. The TV story I was talking about was in Stuttgart where they have the Porsche Museum and the Mercedes Museum and you can rent both.
You understand correctly. Is the steel/Pitt thing a common expression, or one you just made up? I’ve never heard it (but then I’ve never been to Pittsburgh either)