Liftable pusher axles are the newest variation of 6x2 axles. They are suitable for fleets with diminishing loads where the full carrying capacity of a tandem axle is not needed all the time.
When operating in the down position, a liftable system performs like a conventional 6x2 system, with one drive axle and one free-rolling axle. When the full capacity of the tandem is no longer needed, the pusher axle is retracted off the road surface.
An additional 1% fuel economy improvement over non-lifting 6x2 systems is possible with liftable 6x2s.
of 1% over traditional 6x2s.
in certain situations through positioning of the drive axle behind the fifth wheel.
on the free-rolling axle tires as well as other tires.
due to the axle in the up position giving the truck an effective longer wheel base.
since tollways typically charge by the axle.
by providing a visible cue to the fleet’s commitment to improved fuel economy.
The pusher axle requires a more expensive drop center axle.
Some fleets spec a heavier capacity front axle along with higher rated kingpins, bushings, and shock absorbers, plus heavier front suspension components and higher capacity tires.
Utah does not allow liftable axles that are not steerable and most of Canada has restrictions.
They are best suited for fleets with diminishing loads where the full carrying capacity of a tandem axle is not needed all the time.
As a very recent development, there is no residual value comparison available.
For general benefits of 6x2 axles see 6x2 axles page.
Inn 2015 Volvo Trucks North America rolled out its Adaptive Loading product. The Volvo-driven technology developed with Link Manufacturing drives the rear axle in the tandem thereby making the front axle free. An electronically controlled axle lift for this forward axle offers load biasing in poor traction or actual lifting of the free rolling pusher axle clear of the pavement for additional fuel savings over those achieved with the regular 6x2 configurations.
Mack Trucks introduced the same product under the Lifting Pusher Axle name.
Hendrickson Truck Commercial Vehicle Systems’ originally announced the OPTIMAAX system in 2014 as a 6×2 solution with a liftable axle in the forward tandem position. Hendrickson has since refined the OPTIMAAX and will announce the launch OEM in 2017. A Hendrickson developed controller will manage the lift function as well as load biasing for traction. The system is expected to provide performance and benefits similar to Volvo’s Adaptive Loading with the added flexibility of availability at multiple truck OEMs.
Driver training and understanding of liftable 6x2s is critical.
Training needs to focus on:
Fleets must implement a thorough communications and training plan to offset such biases. Major points that should be addressed include:
Major study conclusions include: