In the world of vocational trucks — those plying the trade in the construction, refuse, concrete delivery and logging markets, for example — suspension systems are put under a lot more strain compared to their over-the-road brethren and thus garner a lot more attention.
“The suspension is a very critical component on vocational trucks. It's on the same line of importance as the engine and transmission,” says Tom Vatter, vp-sales and marketing for Hagerstown, IN-based Autocar LLC. “Cost is always a consideration, but durability is king, followed by ease of maintenance. We've found fleets are willing to pay a little more if they get a suspension they don't have to touch much in terms of maintenance.”
That being said, though, ride and handling are becoming bigger issues for some of the same reasons cited by OTR fleets — mainly in improving driver retention and reducing wear and tear on the vehicle. “There is now more air ride in the vocational market,” says Stephen Ginter, vocational products marketing manager for Mack Trucks, now headquartered in Greensboro, NC. “Air ride's distinction is that it's comfortable for the driver when the vehicle is both empty and loaded.”
Air ride suspensions can't be used in many vocational applications; in the refuse market, for example, landfill service exposes the truck to sharp-edged debris, which could puncture the air bags. Fleets are definitely giving them more consideration, says Ginter. “A fully loaded vocational suspension, either spring or air ride, will provide a comfortable, stable ride,” he explains. “But … an air suspension is easier on the body and the equipment, both loaded and unloaded, compared to heavy mechanical suspensions, which are somewhat harsher-riding when unloaded.”
In terms of future directions for vocational suspensions, Ginter says the focus will be on developing more lightweight designs with the same or better stability for high center of gravity equipment, lower maintenance, plus easier and more inexpensive rebuilding of wear points.
“Customers are also very interested in the ability of the suspension to reduce tire wear by maintaining proper orientation to the ground or road surface as the suspension works and articulates through the working range of motion,” he says. “On top of that, remember that a little maintenance will go far in terms of lubrication and re-torquing, while attention to proper axle alignment will pay back in reduced tire wear and longer suspension life.”