Big GM SUVs Get Aero Treatment

September 27, 2005

General Motors executives are confident the 2007 Chevrolet Tahoe will sell regardless of record fuel prices. In part, they say, it’s because they did their homework on aerodynamics. And that’s what gives the full-size Tahoe, with its estimated 20–mpg fuel-economy rating, better EPA ratings than the mid-size ’06 Kia Sorento.

John Cafaro, the top designer on the full-size truck project, says the new SUVs spent a lot of time in GM's wind tunnel, where experts who had worked on vehicles such as the Chevrolet Corvette uncovered new ways to improve the Tahoe's coefficient of drag. "They know all kinds of tricks," Cafaro says, and GM used all of them to move the Tahoe from a coefficient of 0.4 or more to a 0.36 coefficient of drag. The big changes included eliminating the gaps in the front of the vehicle so the Tahoe now offers a smooth, tailored face to the world. In addition, the gaps between the bumper and front fascia and around the headlights have been completely eliminated. Designers also changed the angle of front windshield by moving it out at the bottom. The also reshaped the A-pillar and mirrors and rounded the bottom of the doors to help make the vehicle more aerodynamic.

The results have been impressive with some observers, such as Joseph Phillippi of AutoTrends Consulting, observing that the vehicles actually look smaller than the older models even though the basic dimensions are identical.

The aero improvements get help from GM’s standard displacement-on-demand system, which turns off four cylinders in the 5.3-liter V-8 engine under light power demands. None of the Tahoe's competitors, which include the Ford Expedition, Nissan Armada and Toyota Sequoia, offer the setup nor can they match the Tahoe's fuel efficiency.

All this new efficiency helps mask the added heft built into the Tahoe. The new edition actually weighs about 200 pounds more than the older version because of new crash protection built into the vehicle to help meet new federal safety standards. —Joe Szczesny

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