At a quarry in Easton, Pennsylvania, I got a chance to see just how well-suited Command Steer, Mack's active steering system, is at managing 20,000-pound steer axles over rough jobsite terrain.

Command Steer combines an electric motor with the truck’s existing hydraulic steering. The motor is upstream of the hydraulic steering gear, so the steering gear recognizes only the torque from the steering column input shaft. The steering gear doesn’t "know" there’s a motor helping the driver turn that shaft. It responds as it normally would, turning the output shaft X degrees for every Y degree of input.

The driver is certainly aware of the motor’s presence. It applies up to 11 newton-meters (about 8 lb-ft) of torque to the steering shaft — which means the driver doesn’t have to.

“With a Mack steering wheel, the force is equivalent to 10.67 pounds of assist,” said Mack Construction Product Manager Tim Wrinkle. “If you can picture it in your mind, it’s like having a bowling ball on the edge of that steering wheel to help you turn that truck.”

There’s no difference in the steering performance or road feel. Turning the steering wheel is just much easier and less tiring for the driver.

It works in the opposite direction, too. Command Steer suppresses the input often felt at the steering wheel due to uneven terrain, large rocks, fallen logs, and the like. The motor reacts to those irregular forces hitting the wheels by countering with an applied force of its own, thus reducing steering wheel “kicks.”

In situations that would sometimes see the steering wheel nearly jerked out of the driver’s hand, the driver feels almost nothing as the system steers the truck in the intended direction.

An array of sensors collects data on what the truck is doing and what the driver wants it to do by comparing the rotational angle of the steering shaft with the position of, and inputs to, the output of the steering gear.

If the position of the wheels does not agree with the driver’s input to the steering shaft (for example, when hitting a large rock or a pothole), the system determines that the driver doesn’t want to turn, and therefore keeps the truck on the driver’s intended track.

Command Steer collects data over 2,000 times each second, Mack says, monitoring road conditions, driver inputs and environmental inputs.

“If the driver isn’t changing the steering wheel position, the system will compensate by applying a counterforce to the steering gear to keep the truck going straight,” Wrinkle says.

“Command Steer has been shown to reduce driver effort by 85%, which all goes toward improving jobsite safety and driver productivity.”

Where the Rubber Meets the Potholes

Mack Trucks launched Command Steer for Anthem highway trucks in 2020. The Granite line of vocational trucks got Command Steer about a year later.

At a quarry owned by long-time Mack customer H&K Group, Mack crews laid out a short serpentine course on the floor of a gravel pit about 200 feet below ground level. In another section of the quarry, they had dug shallow trenches, 4 to 8 inches deep and offset by several feet in some cases.

Testing the Mack Granite with Command Steer

I first ran the course in a Granite not equipped with Command Steer Granite with the system.

The difference was like night and day.

Without Command Steer, a good driver could manage all the turns while going quite slowly. It took some pretty aggressive tugs on the wheel, and you had to be quick about it. The Granite has a nice firm steering feel, but it’s almost impossible to “whip” the wheel around.

With Command Steer, on the other hand, I could literally one-finger steer the truck through the serpentine, and I could make the turns fast enough to traverse the course at a decent speed.

There was a backing maneuver, too, where I was able to one-palm the wheel to swing the heavily laden truck (about 74,000 pounds, Mack told us), into position.

But the clincher was the trenches. Without Command Steer, it was difficult enough just staying in the seat while dropping the big front wheels into the offset trenches. The push-back on the steering wheel required more than a little effort to counteract. The tires were pushed and pulled as they dropped into the gouges in the ground, and all that externally induced torque (bump steering), of course, came right back up the steering column.

Command Steer tamed that completely. Where I had worked to keep the non-equipped truck in a straight line, I was able to lift my hands off the wheel of the Command Steer truck while it steered straight through the trenches, unperturbed by the external forces acting on the big tires.

In the days before power steering, many drivers suffered broken wrists and fingers while wrestling steering wheels under such conditions.

I can say the difference between Command Steer and not is about as dramatic as the difference between power steering and "arm-strong" steering.

Testing the Mack Anthem with Command Steer

Mack brought a couple of Mack Anthems to the quarry as well, with and without Command Steer.

Bobtailing around a gravel pit hardly does the system justice, but I did get a sense of the system’s capabilities. The Anthem course was somewhat less aggressive, and included a couple of right and left turns, a backing maneuver, and shallower trenches.

It was a good demonstration of the system's centering capabilities. The steering wheel always swings back to center automatically after a turn. While backing, in particular, a savvy driver would let the system self-center while straightening out rather than risk over-steering and blowing the backup maneuver.

And like the Granite, driving through the trenches, the truck motored straight through the ruts as if guided by some higher power. It never wavered.

Pretty cool.

I have neglected to mention up to this point that Command Steer is sensitive to road speed. As speed increases, its influence on the steering wheel diminishes.

At highway speed, the steering feels exactly as you’d expect a non-Command Steer truck to feel. It’s invisible until it’s needed, and even then, you might not notice it.

In a stiff crosswind, for example, the system counters the forces trying to push the truck right or left by applying a small amount of torque in the opposite direction. The driver will feel almost nothing but a little less tired from counter-steering into the wind.

It will also respond in the case of a steer tire blow-out or if a steer tire slips off the edge of the pavement. The driver will not have to fight to bring the truck back. Command Steer does it for you.

ROI on Command Steer

Command Steer won’t reduce your fuel consumption or help keep air in your tires, but it will be a hit with drivers, especially those that work in challenging environments. Driver recruiting and retention is no less of a challenge for fleets than compliance and cost reduction, so this little tool will pay dividends of its own, though they may be less tangible.

I thought it did a remarkable job with the heavy Granite trucks and their 20K steer axles. Steering through the serpentine was a cinch and maintaining a straight vector through the offset trenches was ridiculously easy. In fact, Command Steer did all the work.

It feels odd at first to swing the wheel of a big truck with so little effort. We’re accustomed to the stiff feeling of traditional hydraulic power steering systems, so being able to turn that wheel with less effort than I need to steer my car was strange, at first. But I got used to it pretty quickly.

Watch Mack's Command Steer in Action

A version of this article appeared in the November/December 2022 issue of Heavy Duty Trucking.