By just looking at the 2014 GMC Sierra 1500 (or the 2014 Chevy Silverado 1500, for that matter), you wouldn’t assume it to be very streamlined. True, it’s no 2014 Corvette Stingray, but as far as trucks go, it’s quite impressive. The formula is to make sure every component contributes to the overall airflow around the half-ton pickup.
“We can’t stop air; we can only guide it through the path of least resistance. It’s like electricity, without the shock,” said Bloch, GM aerodynamic performance engineer. “The biggest misconception is that it’s all about single components. But a certain side mirror design doesn’t create a certain amount of drag, its interaction with the rest of the vehicle does.”
For instance, the airflow around the 2014 Sierra 1500’s air dam below the front bumper reduces drag because it directs air toward the ground, rather than the truck’s rough underbody. At the same time, the 2014 Sierra 1500’s ducted flow path between the grille and radiator prevents air from swirling inside the truck’s front cavities.
To further optimize the aerodynamics the tail gate of the all-new Sierra and the top-mounted center braking light are fitted to guide air cleanly around the truck. And because Bloch’s team detected unwanted airflow between the cab and bed, new sealing has been added.
“We discovered that in the computational analysis we perform,” said Bloch. “The most harmful air between the cab and bed was coming over the cab and down through the gap, so we paid the most attention to that specific area.”
The benefits to all of this work? Improved fuel economy, and decreased wind noise.
To set the record straight, Bloch dismisses the old wive’s tale of leaving the tailgate down or removing it completely as a way to improve aerodynamics. In reality, that action does the opposite. This is because as air flows over the truck, it falls over the cab and pushes forward on the rear of the truck. With the tailgate down, the benefits of that airflow are diminished.
When it comes to truck accessories, Bloch recommends soft tonneau covers and running boards to further reduce the drag of the truck.