air dam material
 

I have heard people saying that they used sheet metal to make their air dams, but has anyone tried aluminum flashing? Just wondering how well it works compared to sheet metal.

If you hit an incline or something and bottom out, the steel will bend back into place. Aluminum does not, it will break.

Black coroplast. It bends right back even after a good whack. Some people use lawn edging, it's forgiving to a smack, too.

I used coroplast for the airdam on the TDI. I installed it in march and it's holding better than I thought it would. It almost looks as good as new. I scraped it down a couple times, but it flexes nicely and comes right back in place. I can not think of an other material that could have done a better job honestly. Also, if you have a longitudinal bend in your dam, the coroplast will resist real good to transverse forces, it won't bend under the car at speed.

Where could I get black coroplast or should I just use lawn edging? And it doesn't bend at high speeds? What did you attach it with, just sheet metal screws? How well does it hold paint?

I bought a roll of lawn edging but, imho, it was too floppy and easily bent to stand up to an oncoming 60 mph wind. I could picture it folding back flat.

Coroplast is pretty stiff and can hang in there against the wind, not to mention against the occasional curb or steep driveway entrance (I should know!).

I installed mine by first folding it over the edge of some 1" X 1" aluminum angle. I'll have to post some drawings of how I did that, it seems to be working out well. The 'plast is pop-riveted to one of the angle legs, wrapped around the angle to the other leg, and then #10 X 1" sheet metal screwed to the underside of the car.

From the front to back, we have coroplast (with pop rivet "good sides") facing out, then one leg of the aluminum angle (with the pop rivet "ugly sides") facing the back.

From bottom to top we have the other angle leg (with the screw heads), the layer of folded-over 'plast, then the underside of the car (penetrated by the screws). Held this way, the 'plast is backed up by the angle pretty well against oncoming wind and obstacles.

Edit to add: I got my coroplast at a local sign shop. It was a special order 6' by 2' black piece, cost me $12. It's easy to trim with a knife or scissors but gluing it may be a challenge.

Have a look at my TDI in the garage entry, you'll see the airdam. I just screwed it in the lip under my bumper with 7 screws. I actually got white coroplast covered with black vinyl which was leftover from a sign shop job.

Has anyone tried Kydex (thermoplastic) for an air dam?

I haven't yet but I'm trying to get my hands on some, I love the stuff, easy to form with heat, EXTREMELY rugged and looks pretty good to boot. If you know of a good place to get it for a reasonable price i'd be interested to hear as I am not sure if my source will come through or not.

I did mine out of aluminum siding because it was free. True, if you kink it to a sharp bend, itll break sooner than steel. But I had no problems with it breaking as I was forming it. I even folded the ends back and relocated the bends a couple times on the drivers side. Also if you bottom it out, itll most likely fold over gradually and you can pull it back. You wont actually land the entire front end of the car flat on the road. Also a plus is that it is more malleable than steel, so at the absolute worst if I lose it somehow, itll deform rather than poke a hole through my steel gas tank or oil pan or other things. I dont see that ever happening though, it is on there better than the airdam on my 6000 wagon and that one is still there. Really it is quite rigid though with a longtudinal bend at top and bottom.