>To the best of my knowledge an air dam does one thing that has
>several possibly
>good side effects - it keeps air from flowing under a vehicle from the front.
>
>The side effects I know of are
>
>o less air flow under the vehicle lowers drag
>
>o the air pressure under the vehicle is lower, enhancing grip; side skirts can
>help this, as well as extending the effect rearward
>
>o if the radiator is in the front and open to the underside of the vehicle, it
>may enhance cooling

Airdams INCREASE drag by increasing frontal area; most are never
tested for aerodynamics, either.

Their purpose is usually for appearance. Those actually designed to
WORK operate by reducing the volume of air passing under the vehicle
in order to stabilize the vehicle laterally.

Enhancement of grip cannot occur at normal road speeds and is only of
appreciable value on the racetrack.
--
Andrew Grebneff
Dunedin
New Zealand
<andrew.grebneff@stonebow.otago.ac.nz>
Seashell, Macintosh, VW/Toyota van nut