Air ride suspension design should optimize fuel efficiency and tire life, notes Bill Wakefield, senior manager, trailer product strategy at Meritor. “That involves maintaining proper alignment of axles as the trailer travels down the road,” he states. “A design that eliminates excessive movement of suspension components will reduce uneven tire wear and tire-to-road surface resistance.”
“Our engineering design parameters for trailer air suspension systems are focused on fuel economy, tire and wheel end life, braking, weight and corrosion,” says Randy Flanagan, marketing and sales director for trailer systems at SAF-Holland. “Over the past few years, we have introduced new models of air ride sliding as well as fixed frame suspensions that meet those criteria.”
Itamar Levine, director of sales & marketing at Hendrickson Trailer Commercial Vehicle Systems, points to the company’s recently launched “shockless” Zero Maintenance Damping (ZMD) system as the latest in air suspension design. “ZMD air springs integrate the damping function traditionally performed by shock absorbers within the air spring by exchanging pressurized air through interconnecting channels between the bellows and piston of the spring,” he explains. “ZMD air springs provide continuous and consistent damping levels, and eliminating shock absorbers reduces maintenance.”
Meritor RideSentry for trailers is an example of a suspension that incorporates an integrated system, which eliminates the need to inspect and maintain the axle to suspension connection. Offered in 20,000-, 38,000- and 40,000-lb. models, RideSentry’s parallelogram design, in which air springs are positioned directly over the axles and upper control arms act as roll bars, absorbs stress on the axle and eliminates dock walk.
Recently introduced by Meritor Wabco is a new electronically controlled air suspension (ECAS) for OEM and aftermarket use. ECAS provides what the company calls “intelligent load transfer” in 6x2 configurations through electronic control of ride height between axles and chassis.
Among the newest air suspension offerings from SAF-Holland is Auto-PosiLift for the SAF CBX40 tandem axle air ride sliding trailer suspension. Auto-PosiLift is programmed to automatically lift the front axle when the system senses that only one axle is necessary to carry the load.
Manufacturers of air springs for OEM and aftermarket use are also refining products. At Aktas North America (Airtech), design developments parallel those for tire technology because air springs require the same types of rubber compounds. Veyance Technologies, manufacturer of Goodyear Engineered Products, develops rolling lobe air springs for truck and trailer applications and custom air springs.
Suppliers are also making the aftermarket selection process simpler. Firestone Industrial Products provides detailed air spring replacement information and notes the importance of selecting the correct spring because even slight changes in design, construction or materials can make significant differences in performance.
ContiTech Air Spring Systems, a manufacturer of components for air suspensions in commercial vehicles, is offering an app for smartphones that supplements the company’s online catalog and cross-reference list.
At Triangle Suspension Systems, the WebSST program enables a progressive search for the correct replacement air springs by a variety of parameters, including vehicle makes and models as well as system dimensions.
Air suspension manufacturers remain focused on roll stability, ride quality and cost-effectiveness, notes Kevin Taeger, heavy duty/OEM sales manager at Energy Suspension, maker of X-Treme Duty polyurethane suspension components. “Many of our OEM customers have recognized that bonded rubber bushings limit the degree of air suspension travel, resulting in failure,” he says. “Polyurethane bushings have greater tear resistance than rubber and are designed to eliminate fatigue, causing less downtime.”
Watson & Chalin’s SL-2065 Tru-Track is a 20,000-lb. capacity self-steering axle and lift-suspension system. The SL-2065 weighs 1,327 lbs. and “maintains the durability and features of the Tru-Track family by delivering outstanding maneuverability with an industry-leading 25-deg. wheel cut.
Reyco Granning’s newest air-ride slider trailer suspension, the DockMaster 400 (DM400), is designed for increased strength, making it ideal for newer drivers that may put added stress on suspensions due to increased curbing, the company said.
Ridewell expanded its RAR-240 series of trailer air-ride suspensions to include yoke mount suspensions designed for use with Ridewell brand axles with Wabco PAN 22 air disc brakes, the company said.
In one design, the yoke trailing arm beam allows the brake actuator to be placed under the tail. A second model is available when brake actuator ground clearance and protection are critical. This design adds a “banana beam” that allows the brake actuator to be tucked between the beam and trailer frame.
Given the range of benefits that air suspensions provide, their popularity on commercial vehicles in North America continues to grow.