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Arminius 05-09-2008 05:50 AM

Suspension Dams on Production Cars
I’ve been thinking about putting some wheel-dams on my car, so I decided to go around and look at several brands of new cars to see how they were designed. I was shocked to see that all had front air-dams, but not wheel-dams, with one exception.

I’ll have to qualify what I just said, later, but here’s what I found.

Ford Focus: The front of the car had a long dam across the entire length, and it was extra low in front of the lowest part of the suspension and steering hardware and half the front tire. This portion that was extra low was about 5 inches long and was clearly meant to direct air around the hardware that attaches to the wheel, but not the wheel per se.

Whether or not the Focus had an air-dam for the back wheels is debatable. What it did have was a large triangular piece of plastic that looked like a bellypan that smoothed out the area just in front of the rear suspension and wheel, but it did not extend below the metal outerbody of the car.

Toyota Camry: This car had a front air-dam that also covered the suspension and half the front tire. The front air dam had a hole in it that looked a little bigger than a quarter, located between the dam and the metal underbody of the car. Nothing special was done for the rear wheel.

Toyota Prius: Same type of front air-dam as the Focus and Camry, but this car had a rear dam that actually covered the entire wheel, and perhaps an inch of the rear suspension where it attaches to the wheel.

Toyota Corolla: This car had a cheap looking air dam that only covered the wheel, but was actually so narrow that it wasn’t covering the entire wheel, and it sure didn’t cover the suspension. My memory of the rear of this car is foggy so I won’t comment on it (but I think it had nothing).

Lexus IS350: The front air dam on this car also covered the lower suspension and half the tire. The rear dam covered the tire and suspension.

Honda Accord: Both the front and rear dams blocked air to the lower suspension, and only part of the wheels.

Honda Civic: Same as the Accord.

It seems that the manufacturers are happy to block the air enough that it misses the suspension and hits the wheel. The dams are just long enough to ensure that the air hits the wheel and then goes around it to the outside of the car, rather then under it.

lunarhighway 05-09-2008 06:59 AM

that's an interesting list! i've been looking underneath cars too to see what i could revese engineer to suite my car.

i'm curently building some dams for my car... they will cover the inner 2/3 of the tire and the suspention link. they'll basically follow the wheelwell inner wall. it will be difficult to test them exacly but if i have them on i'll post some pictures.


here are some random examples i found on the web, i highlighted the actual flaps in red and some parts of the bumper that seem to work together with the flaps in green: (note most seem to guide the air to the middle of the car rather then outside)

also the mercedes and the ford have a separated design with wheel and suspention fairings unconnected and at different angles.
the mercedes has rear deflectors wich i could not see on the other cars

the civic in the first picture seems to be a more storty version and has bigger bulges (green) on the bumper, perhaps these generate some downforce rather than reduce drag.

PaleMelanesian 05-09-2008 10:32 AM

The prius has little flat deflectors in front of the front and rear wheels. The extend directly down from the front edge of the wheel well.

Daox 05-09-2008 10:47 AM

This is the dam on my Matrix. As Arminius said it covers most of the A arm and a little bit of the tire.

lunarhighway 05-09-2008 10:58 AM

seems like they all primary try to keep air out of the front wheel well wich has to be wider to allow for steering. that would explain why there's fewer cars with rear deflectors

BBsGarage 05-09-2008 11:31 AM

06 Corolla

In the process of trying to improve these.



ebacherville 05-09-2008 12:20 PM

very interesting , also there relying on air flow to get the air moving around instead of smooth body mods.. not the most efficient but workable.. air flow will create the smooth flow but not as efficiently, the reason they do it this way si that it adds added ground clearance for the car.. Ideally they would have side skits and nice low airdans from the front of the car , this however makes speed bumps etc.. hazardous..

IF all roads were designed for low to the ground long nosed highly areodynamic cars there would be no parking lot speed bumps etc.. ..

One Idea I have been tossing around was hydrolic or air suspension to raise the car up when driving in hazard area like drive ways and parking lots, but on the free way allow the car to drop nice and low to the ground... to a low stance for MPG. Even toyed around with a adjustable front nose angle, like the concord jets, they can adjust the angle of there nose.. for landing a such.. you could even make it linked to speed or gear selection, put it in 5th and it drops the nose section down to MPG mode..

lunarhighway 05-09-2008 12:42 PM

i drive around town in 5th ;)

i've been wondering... woudn't a partial infaltable nose be workable? make the whole nose out of rubber, maybe sectioned and pump it up... it can be shaped aerodynamically, will deform on impact and should pressure leak you can reinflate it same as the tires... in fact it might not even have to be really pressurised to keep it's shape, but that way it could also serve as an actual bumper... (some airbag tech to deflate/inflate as appropriate to minimise the crash effect would be nice too, because all these modern cossision prevention measures won't do much is someone decides to hit you

back to the real world it's quite understandable carmakers take such a coarse approach... looking at the aerodynamics of cars i see in dayly traffic it's unbelievable how much airdams etc at the front of the car, have been mangled torn or just clean ripped off...

ebacherville 05-09-2008 01:08 PM

yeah thats the problem, most roads are very non low car friendly, especially in towns and city's highways are not to bad..

Now if you could adjust or alter that nice low nose at slow speeds or just lift the car up 3" through hydrolic or air shocks, you'd have the best of both worlds.

Porsche makes the spoiler on the back of there 911 rise up at higher speeds.. we could figure out a easy way to do it with the nose or lower part of the air dam.. Linear actuators are pretty cheap and can provide hundreds of pounds of force.. enough to move the nose up or down a few inches..

As for crashes etc.. my nose on my project car will be all insulation foam.. its how ill sculpt the new nose for it.. it will also provide some great crash protection with 3 feet of foam in front of the car :)

lunarhighway 05-09-2008 03:33 PM

some real high end cars have these electronicly controled "drive modes"... mostely sport mode or something that controles engine management, sometimes gearshift points on an automatic gearbox, but also suspention stifness and all these new abs and what not safety features, i'm sure there's cars out there that later ride hight.

come to think of it, the old citroens like the DS did have this special suspention that would cause the cars to "sit down" when it was parked and than raise to a cerain level depending on the weight they where carying... these cars had fixed rear wheel fairings

but could lift a wheel of the ground so that it would drop out of the wheelwell and could be removed.... clever stuff for it's time and even now, i even think you could select various ride heights. sooo the technology for variable ride height is definately out there.

in fact later 80's and early 90's citroens had really gread drag quoefficients as well so with a little tweaking and aeromodding that could be an interesing starting point for a project.

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