Test Drive

Class Reshaped

New Peterbilt Model 579 offers a blend of fuel-efficiency enhancements, sleek styling and driver comfort.

The 579’s aerodynamic design can deliver substantial fuel savings.The 579’s aerodynamic design can deliver substantial fuel savings.

Peterbilt has introduced the aerodynamic Model 579, based on an all-new chassis and cab. Andy Weiblen, one of its designers, says the new truck integrates everything that has happened to heavy-duty trucks in recent years.

The truck’s sleek frontal design is striking when you consider that Peterbilt’s legacy was built with large, flat-nosed conventionals.

“We have a responsibility to honor that heritage in a way that says, ‘This is a Peterbilt,’ while giving our customers that absolute latest in modern design and technology to help them compete in the real world,” Weiblen says.

Peterbilt engineers maximized interior space utilization with innovative touches such as this slide-away work station.Peterbilt engineers maximized interior space utilization with innovative touches such as this slide-away work station.

If the 579 looks more compact than most Class 8 tractors, it’s because this is the cleanest, most aerodynamic overall tractor design in Peterbilt’s history. The nose on the new truck is 2 inches lower than anything else the company offers. Every flat edge has been rounded to facilitate airflow. The front windshield is higher and blends seamlessly into an air dam above the cab. The A pillars are noticeably thinner – optimizing both visibility and airflow – while details such as the cab marker lights were subjected to air-fluidity testing to achieve the ideal locations.

Different configurations are available, but the full aero package will deliver 8 percent to 10 percent better aerodynamics than comparable models, which translates to a 4 percent to 5 percent boost in fuel economy, Weiblen says.

It will be offered with Peterbilt’s powertrain offerings, including the Paccar MX and Cummins ISX diesels and Eaton automated and manual transmissions.

Peterbilt has developed a new clutch for use with manual gearboxes on the 579. Most clutches today take about 55 pounds of down-pressure to actuate. But the new Peterbilt clutch requires only about 30 pounds of down-force, a tremendous difference when dealing with stop-and-go traffic.


Driving the 579

Because the test drive unit is due next week for display at the Mid-America Trucking Show and Peterbilt needs to exhibit a pristine fifth wheel, we can’t test the 579 with a trailer. But even a bobtail outing around Dallas and Fort Worth, powered by a 13-liter Paccar MX, reveals a lot about it.

Designer Andy Weiblen says simplicity was the overriding design criteria, and the dashboard is proof of that. The elegantly functional layout neatly packages all the engine information, entertainment options and navigation systems. Large, easy-to-read, softly backlit dials are accented by bold chrome bezels. Stereo, HVAC and navigation systems have been made easier to operate.

The Evolution driver’s seat immediately grabs your attention. A large button deflates the seat down to the floorboard for easier entry and exit. Once you’re in the seat, hit the same button and the seat returns to your preset height. Another switch allows seat compression adjustment to deal with a rough patch of road.

Views from the driver’s seat are outstanding — thanks to the lower nose, taller front windshield and smaller A pillars. Designers expanded the side windows and optimized rear-view mirror placement for clear rear views.

The clean, more compact front cab design, Weiblen says, facilitates a nice flow between the front of cab and the sleeper. In the rear, drivers will find a sleeper outfitted with a work station and hook-ups for flat-screen TVs, laptops and video game consoles, as well as tons of storage space.

I spend a good portion of our drive using the passive cruise control, one of many safety and awareness systems. It radar-tracks vehicles in front of the tractor and adjusts my speed accordingly.

Weiblen says the 579 engineering team used the latest composites and ride-dampening technology on the cab. As quiet as the truck is at rest, it’s amazingly quiet even at full-throttle. The overall design has a lot to do with this, but also the aerodynamic exterior virtually eliminates wind noise. With the windows up, interior noise levels in the 579 are approximately 69 decibels — and those levels don’t rise much at all with the windows down, still plenty low at 65 mph to carry on a normal conversation with your passenger.

The all-new chassis and suspension have taken almost all the lateral sway out of the equation, making for sure-footed handling. The truck doesn’t wander around its lane at highway speeds, even with an occasional blast of wind.



Engine: PACCAR MX13

Horsepower: 455 hp at 1,900 rpm

Torque: 1,650 pound-feet at 1,100 rpm

Transmission: Eaton-Fuller UltraShift Plus automated manual

Cab configuration: 123-inch BBC/63-inch hi-rise sleeper

Front axle: Dana Spicer E1202I rated at 12,000 pounds

Front brakes: Dana Spicer air disc

Rear axle: Meritor RT-40145A rated at 40,000 pounds

Rear brakes: Bendix 16.5×7 cam drum

Rear axle ratio: 3.07


A driver-customized interior

Overdrive Executive Editor Jack Roberts samples the results of Peterbilt’s intensive research on ergonomics.Overdrive Executive Editor Jack Roberts samples the results of Peterbilt’s intensive research on ergonomics.

Designer Andy Weiblen he says the five-year development cycle for the Model 579 was driven by Peterbilt’s most intensive market research ever.

“One of our projects was to take a fully adjustable truck cab and sleeper to truck stops all around the country,” he says. “We invited drivers into the cab and sleeper and asked them to set any component in the mock-up exactly where they would want it if they were designing their own personal vehicles.”

Drivers could adjust armrests, bunk heights, interior cab width or seat positions, among other features. The result, Weiblen says, was a gigantic database of real-world ergonomic data. “We were able to use that information to design a truck that is remarkably comfortable for a remarkably wide range of drivers,” he says.


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