GM mods the Sierra hybrid pickup: aerodynamic tweaks + LRR

[MetroMPG]

From the Winding Road:

In addition to the hybrid system, GM added LRR tires plus a few aero mods - things that could be on non-hybrid models too...

Additional details specific to the Sierra Hybrid include aerodynamic aids. A slightly deeper front air dam and a tonneau cover for the bed reduce air drag, fostering maximum efficiency.

Hmm - a deeper air dam. Remember what Ford did to it's '08 Superduty pickups?

Ecomodder - New: Ford mods their Super Duty pickups ... chin spoiler + final drive changes

[Big Dave]

I'm so unimpressed about GM and Ford chin spoilers.

My 2000 F-350 had a chin spoiler with 7.5 inches clearance - the least that will go over a parking curb.

[Jethro]

As long as the spoiler covers the ugliest parts of the air flow (lowest hanging parts) it's theoretically 'good' ain't it?
After that point aren't you just increasing your frontal area?

[MetroMPG]

Originally Posted by Jethro

After that point aren't you just increasing your frontal area?

You'd think so, but I recently saw a GMC pickup from the side and the stock air dam was quite a bit lower than the lowest underbody components. At the time I wished I'd had my camera - I would have like to post it.

I'm inclined to think the GM aero people found it was worthwhile to extend it down as far as they did.

[JasonG]

I believe the Nascar philosophy is the area under the car is so turbulent, it's better to keep all air out of there.
For some racing vehicles this includes the radiator exhaust as well.
Add the grain of salt to the above, they are also interested in down-force not just cd.
Trucks also have that big rear axle to drag through any air down there. Less air underneath = less to plow the differential through.