A Wabco Electronically Controlled Air Suspension will be available next month through the European company's North American joint venture with Meritor.
A so-called dead tag axle is part of this 6x2 tandem with Electronically Controlled Air Suspension from Meritor Wabco.
A so-called dead tag axle is part of this 6x2 tandem with Electronically Controlled Air Suspension from Meritor Wabco.

The ECAS system, aimed primarily at potential users of the 6x2 axle configuration, is adapted from a product that has sold 3 million in Europe and elsewhere overseas.

ECAS precisely maintains a set ride height between the axle and chassis as road and vehicle characteristics change, and alters air-bag pressure on auxiliary axles as needed for load support and traction, product specialists explained at a demonstration earlier this week near Rochester, Mich.

They showed a road tractor with a 6x2 axle layout, whose tandem has one drive axle and one liftable non-driving, or "dead," axle. Automatic transfer of weight begins when drive wheels lose traction and spin; the truck's traction-control system senses this and informs ECAS's controls, which order a reduction in pressure on the dead axle's springs.

This causes the drive axle to shoulder more weight, increasing traction and helping the vehicle to start out and keep moving on slick surfaces. Controls are set to load the drive axle only to legal limits, usually 17,000 pounds on a tandem. With lighter loads, a greater proportion of the tandem's weight can be sent to the drive axle, specialists explained.

Pressure in air springs is only adjusted when there is a change in the load, so normal axle vibration during driving does not cause height adjustment or consume air. Reduced air consumption decreases the compressor duty cycle, resulting in improved fuel economy, they said.

More customers are becoming interested in the 6x2 concept as they seek ways to cut vehicle weight and fuel use, said Jon Morrison, president and general manager of Meritor Wabco. A 6x2 eliminates the heavy and friction-producing differential and axle shafts used in the second drive axle in the common North American 6x4 tandem.

Most operators here have stayed with the 6x4 because they believe it has better traction; this causes its resale value to suffer. Yet the 6x2 is the rule for highway trucks and tractors in Europe because operators know that transferring weight to a single drive axle enhances traction.

A few LTL fleets in the U.S. use 6x2 tractors, but with either manually adjustable lift axles or dead axles which cannot be lifted. But ECAS is automatic, Morrison said.

"This is a highly differentiated approach to 6x2 applications, which provides several cost benefits to the fleet owner at the point of purchase and over the life of the vehicle," he said. "The ECAS system will not only improve 6x2 traction and reduce fuel consumption, but will also decrease axle wear and tear, requiring less maintenance in addition to several safety benefits."

Safety comes from reduced wheel slip through a combination of weight transfer and torque control done by electronic traction control. An optional air-dump feature allows the suspension to be lowered to ease coupling onto trailers, then raised to resume travel.

ECAS can also be employed on multi-axle vocational trucks, whose lift axles can be automatically adjusted to enhance traction on drive axles, the company said. Meritor Wabco will also seek sales to motor coach operators.

ECAS for North America operates on 12 volts instead of the 24 volts used in European trucks. Otherwise the product for this market is very similar to the proven one from Europe. The company will emphasize use of ECAS with Meritor axles, but it will work with others, specialists said.