Quote:
Originally Posted by Christ
The truck has a natural rake to it, so that the bed actually slopes downward to the cab. I assume by lowering the rear, he's attempting to level the truck out some, so that the bed doesn't act like a forward facing scoop.
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My thought is that the standard rake affects all the fore-body flow,forcing it always into a positive pressure regime as the truck advances.
Lowering the tail takes some of the "wedge" out of the profile and could threaten the energy at the very back of the roof,something automakers have worked very hard to get since the late 1980s.
This could compromise the viability of any bed mods.
Conventional aerodynamic wisdom is to raise the tail as much as practical to achieve the reflex-camber worked out with the banana car.
Trunklid heights have come up on cars and bed rails and tail gates for the same reason on pickups.
If the whole truck could be lowered it might be a better solution.Should a load of "full-capacity" ever be added to the bed,you sure wouldn't want the tail to sag.Very dangerous to stability.
Only testing would reveal a "scoop" effect.The majority of pickups have a locked vortex contained within the bed,often with air flowing backwards over the tailgate into the bed.
Adding a soft tonneau allows the air to strike the back half causing an indentation in the fabric,while the low pressure of the vortex attempts to lift and suck away the forward half.
GM's patented 1/2-tonneau exposes the front face of the tailgate to the low pressure of the vortex and with it,the relative delta-p across the gate for net thrust and a little better mpg.