TRU CKS & T R AN S P O R TAT I O N | By Curt Bennink
Balance Vocational Truck SUSPENSION Trade-offs
Mack Trucks
Advances in vocational truck suspensions provide options that change the weight vs. stability vs. articulation vs. ride quality equation.
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very vocational truck suspension option comes with its own unique performance trade-offs. The best choice requires an understanding of how the trade-offs match up to your application requirements. “Mechanical suspensions are still the most popular for the vocational market thanks to their great stability, articulation and maintainability,” says Tim Wrinkle, Mack Trucks construction product manager. “Air ride suspensions are becoming more common, as they offer a better ride when unloaded. However, these suspensions can be limited in articulation and stability. “Driver knowledge and training are also very important with air suspensions because drivers need to evacuate air bags before dumping the load,”
he adds. “Depending upon the setup and a driver’s experience, this can also slow the dumping process for dump trucks.” “Although there is a trend in spec’ing air suspensions for vocational applications, there are trade-offs between off-road and on-road performance,” agrees Peter Schimunek, marketing segment manager, Western Star. The job of the suspension is to support and cushion the load. The suspension absorbs shock loads that would otherwise be transferred into the frame. If the truck frame is doing the job of the suspension by twisting and absorbing shock, then it stresses every component of the vehicle, eventually causing failures and maintenance issues. Understanding the application and performance demands is the first step. The capacity of
36 EQUIPMEN T TODAY | August 2021
The Mack mRIDE provides extreme articulation and constant tire contact, delivering enhanced traction on rough terrain. The spring leaf design and V-shaped torque rods help ensure stability to efficiently transmit forces into the truck’s frame. the suspension; whether it is for a single, tandem or tridem configuration; if the system is for a tractor or straight truck; and the nature of the terrain all play a role in narrowing the choice between air, rubber or steel springs. There are multiple suspension options available to meet the many niches in the vocational truck market, each with unique features and benefits. Compare the suspension choices available to meet application needs — reducing weight, improving off-road mobility, increasing stability, minimizing torque reactivity or all of the above — while balancing upfront cost. The type of loading and
unloading performed must be considered. A dump truck hauling aggregate requires a different suspension than a mixer truck, for instance. There is more of a shock load factor when aggregate is loaded vs. ready-mix. In addition, a stationary load has different needs than a moving load, such as liquid bulk haul or a concrete mixer. Be sure to account for worstcase scenarios. Sometimes the truck may be required to take on heavier loads than it usually does. These temporary loads may require a higher creep rating on the jobsite, thus requiring a heavier-duty suspension. Where the truck will operate — the type of terrain — can create
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different needs for articulation and ground clearance. Serviceability gains importance in remote locations. For example, if it is going to be in the middle of an oil field with no immediate access to a dealership, it’s important to spec the suspension to be serviceable by the driver.
NARROWING THE GAPS Avoid relying on past history to spec today’s suspensions. Suspension designs have become more streamlined and versatile over time. In the past, bigger, bulkier and heavier suspensions suited for tougher applications also provided a rougher ride. With the introduction of air ride suspensions and other innovations, drivers now have a more comfortable ride and the loads are better protected from rough terrain. There used to be a large gap between the comfort of on-road suspensions and the durability and stability of their off-road counterparts. The gap has closed significantly in recent years, with off-road suspensions getting very close to matching the comfort and performance of those targeted for on-road applications. Mack recently made improvements to its mRIDE mechanical suspension. “The Mack mRIDE spring leaf over rubber block suspension is ideal for customers needing improved stability and greater traction on jobsites,” says Wrinkle. “The mRIDE’s parabolic springs are thickest at the center to ensure the clamp load area offers the greatest strength, and are tapered to improve driver comfort.” The improved suspension provides extreme articulation and constant tire contact for greater traction on rough terrain. “The spring leaf design and V-shaped torque rods help ensure stability to efficiently transmit forces into the truck’s frame,” says Wrinkle. “The Mack mRIDE has been our lightest vocational proprietary rear suspension and earlier this year we lightened it even further, now offering additional weight savings for increased payload when paired with proprietary Mack axles,” he adds. “Available at 40,000- and 46,000-lb. suspension ratings and with standard track axles,
