tire dams proper angle
 

i was thinking as the car roles forward the wheels themselfs would create drag so was wanting to divert the air away from the wheels before it gets there.
heres my delema what angle is the best and where to divert the air too
which would be best:
flat [ (=)
down =| (=)
divert air under the car /| (=)
divert all out the side of the car \| (=)
50% under 50% out <| (=)

other ideas anything

FWIW, from a not very scientific observation of the dams on multiple makes
of cars, -- cars of European and Asian origin are most likely to have them --
the industry convention, if not standard, seems to be:

* The front air dams are ~2.5 in. high, and ~1.5 x tire width with the outboard
end of the dam roughly at the tire centerline. (This suggests to me that airflow
just in front of the front tire is angled outward and not parallel to the
centerline.)

* The rear tire dams are about 2 in. high, and the outboard end is only slightly
offset inward from the outer edge of the tire.

* When installed at the front edge of the wheel well, air dams are installed
perpendicular to the centerline, and perpendicular to the road surface, that
is, they point straight down.

Yea, you definitely dont want them at an angle as they will produce [more] lift.

As for the front flaps, the best I have seen are on some newer bmws and audis, they actually wrap around the inside of the tire to promote the air down the center of body.

A key thing to remember is these flaps add drag to reduce drag. So you want to keep them fairly small (the numbers listed above are right on as far as what I have seen).

However, even I wonder if the rear tire flaps could be larger than what we typically see. Surely the rears are subject to lower pressures. The OEMs just dont want something to gaudy that might get ripped off.

Also keep them mounted as close to the tire as possible (preferably inline with the start of the wheel well). Some manufactures (like honda, actually, i think, only honda) have very poor designs, sticking the flap apparently anywhere under the front bumper.

Ive also wondered about a pressure relief system. Perhaps one could increase the size of the flap, to make it more effective, if it had slots built in to relieve the pressure buildup and decrease the size of its wake.

I think something like this can be seen on the new mazda 3's, however there is speculation as to the actual reasoning behind the slots.