Quote:
Originally Posted by aerohead
Apology for another 'better late than never response.'
This is a really important question. I skimmed the old Sport Truck Magazine pickup aero article recently, and I believe that they directly address this question.
So as not to get it all wrong, I'll review it over the weekend and have something to bring next Monday.
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From Glen Sharpf, Senior Development Engineer, General Motors Corporation:
During R & D of the GMT 400 project truck ( which became the 'new' GMC/ Chevrolet pickup ), a full tonneau reduced aerodynamic drag: It increased air pressure on the front of the box and decreased pressure on the front of the tailgate.
A half-tonneau was more effective in reducing drag... It did so by relieving even more pressure on the front face of the tailgate.
( a bulkhead placed beneath the leading edge of the half-tonneau isolated the front face of the tailgate from the low-pressure core of the bed vortex, increasing drag ).