Push it real good: The role of pusher axles in trucking

Push it real good: The role of pusher axles in trucking

As someone who hasn’t lived under a rock for the past 30 years, it’s fair to speculate you’re familiar with Salt-N-Pepa’s 1987 mega-hit “Push It.” And as a fleet manager, I’ll venture that whenever you hear it, there’s one component you can’t get off your mind for the rest of the day: pusher axles (if that’s not the case, it is now).

Most commonly found in vocational applications, especially on dump trucks, refuse trucks and mixers, pusher axles are in the same family as tag axles when it comes to 6×2 configurations, where only one of the two rear axles receives power (as opposed to 6×4, where both of a tractor’s rear axles are drive axles).

Both pusher and tag axles are non-powered and can be liftable or stationary axles. The goal for both is to help the truck achieve maximum productivity by increasing payload and distributing weight, says Steve Mastroianni, senior manager of product planning for Dana.

“Whereas a tag axle is located behind the drive axles to take some of the weight off the rear drive axles when the vehicle is fully loaded, a pusher axle is positioned in front of the drive axles, adding stability to the chassis during cornering,” Mastroianni says. “The decision to spec either configuration is generally based on load balancing of the vehicle. For handling and weight balance during transport, one or more pusher axles to support the load may be required. Even while dumping a load, the weight is transferred to the rear-most axle, offering the necessary additional support at the rear of the vehicle.”

Do you need a push?

When deciding whether to spec a pusher axle for your truck, first thing’s first: Always consult with the vehicle manufacturer to ensure you’re selecting the proper axle type for your application.

Beyond this, there are several considerations in deciding whether to include a pusher or tag axle in a truck. Some of these considerations for a dump truck, for example, according to RaNae Isaak, powertrain and TCO consultancy leader at Cummins Inc., include:

  • federal regulation,
  • the state laws including bridge and frost that may impact operation,
  • the time spent off-road,
  • the duty cycle of the vehicle,
  • the weight of the commodity,
  • the potential efficiency gained,
  • and the maneuverability expected.

“Framing these considerations with expected lifecycle in mind will help fleets reliably plan for overall asset utilization,” she says.

Fleets who find pusher axles are right for their trucks’ application often find the benefits can go beyond added payload, Isaak adds.

“As a fleet manager, you might find a better distribution of weight, which can impact the service of the overall vehicle. You may find improved efficiency when heavy (lift axles down) and then when empty (lift axles up), depending on the frequency and operation in which you use them,” Isaak says. “Depending on your operation and business model, you might find additional opportunities to haul different commodities given the dynamic way you spread the vehicle weight.”

Dana’s Mastroianni adds spec’ing a pusher or liftable axle can include a potential for increased performance by the other axles, resulting in less wear and tear on the vehicle’s tires and ancillary components. Additionally, he says, the vehicle should experience improved stopping distance due to the added brakes on the pusher axle.

Maintaining a pusher axle is similar to maintaining the other axles on the vehicle with the added inspection requirements associated with the additional lift air suspension, Mastroianni says, but pushers can show other maintenance benefits as well.

“Theoretically speaking, a liftable pusher or tag axle should experience increased longevity due to the fact that it’s seeing only half the duty cycle of the other axles on the vehicle since it’s lifted half the time,” Mastroianni says. “Additionally, long life features, such as those provided by Dana on various steerable pusher axles – low maintenance king pin; dual draw keys for durability and reduced tire wear; and one-piece, lightweight forged knuckle for lower weight and reduced parts complexity – can reduce overall service requirements and extend time on the road.”

Cummins’s Isaak adds the main consideration regarding maintenance intervals for Cummins engines is the duty cycle of the vehicle, and the company has a different maintenance schedule for vocational applications. For vocational customers, the X12 provides an oil drain interval of 1,500 hours, 18 months or 40,000 miles, whichever comes first; whereas the X15 has 500 hours, 12 months or 20,000 miles for an oil drain interval.

“Serviceability may be affected by the engine location compared to axle placement, but there is not a unique difference in intervals based on the specific axle choice,” she says.

Of course, that ability to carry more payload often comes with some potential trade-offs as well. For example, says Tony Sablar, Peterbilt vocational marketing manager, these axles add complexity to the vehicle, take up more frame space and may negatively impact maneuverability.

“A pusher or tag axle may negatively impact maneuverability due to the scrubbing effect of the additional tires,” Sablar says. “Steerable pusher axles will help limit the amount of tire scrub, but it will still exist. Lifting the pusher axle may be allowed in slow speed applications. In these cases, the steer and drive axle manufacturers have published ‘creep’ or ‘job-site’ ratings that allow a truck to load the axle over its nominal rating at low speeds.”

He adds, “Some vocational body types and applications will not work with a typical tag axle due to its location.”

Lifting the limits

A truck’s turn radius is one of many factors affected by adding a pusher axle. In the case of a dump truck, for example, spec’ing a pusher axle over a tag axle could result in a less flexible turn radius.

“However,” says Cummins’s Isaak, “depending on the maneuverability requirements within the customer’s route, this might not be an issue. With the development of lift-capable pusher axles, the turn radius and maneuverability can be improved, as long as weight limitations are not limiting the ability to lift the axle.”

Mastroianni says Dana works with various niche specialty vehicle builders that integrate Spicer steer axles and components as part of their liftable, steerable axle solutions, in order to provide improved turn angles and optimal performance.

“Dump trucks spend most of their time at job sites or driving on urban roads between job sites, where tight turns and cornering can be routine,” he says. “In this case, a steerable, liftable pusher axle that aids in maneuverability and allows the axle to remain in the lowered position as needed would maximize productivity.”

Are pusher axles a good fit for over-the-road use? Click here to find out.

You May Also Like

Goodyear says tires-as-a-service may help fleets save money

Goodyear said the subscription service can help fleets improve TCO, increase uptime, reduce breakdowns, decrease fuel consumption and more.

Goodyear-Tires-as-a-service-TaaS

Goodyear Tire & Rubber Co. said its new tires-as-a-service (TaaS) offering combines the company’s tires, predictive insights and footprint into one subscription-based solution. Building on the company’s Total Mobility program, Goodyear said that it will manage end-to-end tire service for its customers.

Available for commercial and last-mile delivery fleets in the U.S. and Europe, Goodyear adds its TaaS offering can help save time and improve total cost of ownership through outsourced tire management from this subscription-based solution. According to the company, this is designed to increase uptime, reduce vehicle breakdown events, decrease fuel consumption and more.

Davco Technology appoints Tim West as new president

Before joining Davco, West most recently served as VP of seating and structures, Vehicle Solutions Division at Commercial Vehicle Group, Inc.

DAVCO-president-Tim-West
PRT launches new strut assemblies for ProMaster, Silverado, and more

These new items cover more than 15 million vehicles and include models such as the 2023 Ram ProMaster 1500, 2023 Chevrolet Silverado, and more.

prt-for-web
East opens Aftermarket Parts Facility in Kent, OH

In addition to East trailer parts, the facility will carry common parts for all makes and models, such as airbags, lights, wheel ends and more.

East-new-facility-larger-photo
Lucas Oil facilities achieve ISO 9001:2015 recertification

The Quality Management Systems certification included both Lucas Oil production facilities in Corydon, IN.

Lucas-Oil-ISO-Certification
Other Posts
Navigating fluid options to raise efficiency and reduce downtime

ICE technology is changing, and Valvoline and Cummins say oil plays an important role in your fleet’s efficiency and uptime.

Valvoline-Cummins-oil-ICE-changes-webinar
What is ‘Trucks-as-a-Service’?

We talk with Volvo Trucks about the service that aims to ease fleets into making the EV transition.

Trucking-Sustainably-truck-as-a-service
NACFE: small depots are ready to scale electrification

Dipping your toes into electrification is one thing, leaping into running 15+ BEVs is another. Though NACFE says for many, the time is right.

NACFE-DEPOT-Scaling-Report-Cover-Run-On-Less-BEV-Electrification-fleet-trucks
Beyond a one-size-fits-all trucking decarbonization strategy

Much of the responsibility now falls on the fleet, but that should be a welcome change.

2024-ACT-After-the-Show-Floor-1400