A range of factors impact air suspension design, notes Reyco Granning’s vice president of Engineering, John Stuart. “One requirement showing no signs of diminishing is the ever-present demand for weight reduction,” he says. “If you had told me 10 years ago that the market required a 1,300-lb. slider air suspension, I would have said it can’t be done; yet here we are with products that meet that need.”
Stuart also points to the demand for reliability and ease of maintenance and assembly in air suspensions, and notes that once optional features on axle/suspension assemblies are now becoming standard. Included are air release for slider pins, load blocks, air tank and mud flap brackets and plumbing attachments.
“Air suspensions are commonly spec’d for driver comfort,” says Dave McCleave, director of marketing, Hendrickson Truck Commercial Vehicle Systems, “but are predominantly specified for weight-sensitive bulk haul, beverage, grocery and refrigerated and dry van applications. We have also noticed their popularity among applications in need of equipment and cargo protection, fleets that haul furniture, fragile goods, or experience road hazards.
“Additionally,” McCleave adds, “there are already weight sensitive applications experimenting with alternative fuels that require even more lightweight options to offset equipment that can be as much as 2,200 lbs. heavier.”
OEM offerings like the Freightliner AirLiner rear truck suspension are designed to be lightweight for more payload capacity with aluminum brackets and composite aluminum air bags on some models. According to the OEM, the suspension’s geometry promotes lateral control and roll stability and its combination of trailing arm leaf springs and self-leveling airbags enhances ride whether the vehicle is loaded or unloaded.
Peterbilt’s proprietary Front Air Leaf Suspension includes a wide, flat, lower leaf front spring design to enhance control and an upper leaf for better roll stability and handling. The system is available on some truck models with suspension weight capacities from 12,000 to 13,200 lbs. The design uses four air springs.
Meritor’s RideSentry MPA Series Trailer Air Suspensions in MPA38 and MPA40 models are available for tandem-axle trailer applications in 38,000- and 40,000-lb. capacities, respectively. To provide a smoother ride, according to the manufacturer, the suspension’s parallelogram design integrates components and places air springs directly over the axles.
For LTL use on pups as well as convertor dollies, Meritor offers the RideSentry MPA Single-Axle Trailer Air Suspension (MPA20). A key feature of the RideSentry MPA20, according to Meritor, is no fore/aft axle movement during suspension articulation, which eliminates backslap. In addition, roll-induced steer—a common trailing arm problem for combination vehicles—is also eliminated.
The Meritor MTA Trailing Arm suspension family in top mount and low mount versions is designed for a range of vocational applications, including on flatbed, tank and bulk trailers. The suspensions are offered in capacities ranging from 23,000 to 30,000 lbs.
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