Factory installation brings customer benefits
One thing that sets Mack® trucks apart from the rest of the competition is the way Macks can be customized for specialized operations, both through factory spec’ing and aftermarket customization. For years, one popular aftermarket customization has been the addition of a liftable “pusher” auxiliary axle, which is positioned in front of a tractor’s tandem-drive axle to enhance weight distribution when the trailer is loaded and reduce fuel spend and tire wear when it’s running empty.
Starting in the second quarter of 2023, however, Mack customers no longer need to turn to the aftermarket for the addition of pusher axles, as Mack will factory-install several models of Hendrickson single pusher axles on Mack Anthem®, Pinnacle™ and Granite® tractors. Available will be a 13,500-pound and a 20,000-pound-capacity steerable axle as well as a 20,000-pound-capacity fixed axle.
“Mack dealers and customers have been putting on pusher axles for greater flexibility, and now they’ll be available from the factory, which means there will be no additional work needed and these axles will be covered by our chassis warranty,” says Stu Russoli, Mack’s senior highway product manager.
A trio of liftable axles
The specific models selected by Mack are the Hendrickson Composilite EXS 13,500- and 20,000-pound rated steerable axles and the Hendrickson Toughlift FM 20,000-pound rated fixed (non steering) axle. All three liftable axles have outside-mounted regulators and are lowered or raised by the truck driver via switches mounted on the dash.
“Much of the rise in interest for these liftable axles stems from trucking operations in the Pacific Northwest,” Russoli explains. “Regulations in that region allow for a 105,000-pounds gross combination weight rating (GCWR) for over-the-road tractors when a pusher is added at the proper axle spacing.” He points out that the 13,500-pounds rated pusher axles are also used in other states and provinces for applications that are dependent on weight and axle-spacing regulations. “The 20,000-pounds rated pushers are used across the U.S. and Canada and are typically added to tractors handling heavy hauls, such as those pulling lowboys, flatbeds and log trailers,” he says. “They’re also on tractor-trailers that are commonly used to haul large pieces of equipment, heavy industrial loads or agricultural loads.”
Given that there are many pusher axle spacings used, Russoli advises that truck owners “make sure to check the regulations in the areas that the tractors will be operating in.” For instance, in the Pacific Northwest, pusher axle spacings vary from 60 inches from the center of the front drive axle to the center of the pusher axle all the way out to 91 inches, with many steps in between.
“Those spacings can vary according to the trailer used and its axle spacings,” he continues. “For heavy-haul pushers, the most common setup is to match or be close to the tandem drive axle spacing, so 50 inches or 52 inches are common pusher axle spreads. Again, be sure to check the regulations, because wider spreads are also used, even up to 101 inches in some parts of Canada.”
Bridge to efficiency
Russoli says the purpose of opting for a pusher axle on a tandem-drive axle comes down to gaining efficiency by “taking a bridge-law approach to spec’ing.” In the U.S., the Federal Bridge Formula enables a vehicle to run at a higher GVWR, for greater load capacity, when there are more axles and/or there is more distance between the axles to “spread out” the weight of the load carried. Pusher axles make meeting the bridge formula possible while also saving fuel and tire life when the trailer is unloaded.
“The payback of putting Hendrickson pushers on Mack tractors is to legally haul greater loads and save fuel and tire wear when a heavy-haul trailer is unloaded,” Russoli says. “Factory-installing these axles adds further value by saving our customers time and money after their tractors are delivered.”