For decades pickup truck suspensions were as basic as could be, beginning with solid axles at both ends, each suspended with heavy and stiff leaf springs. More accommodating independent front suspensions did not appear on two-wheel-drive pickups until the 1960 Chevrolets and 1965 Fords. Eventually IFS made it onto four-wheel-drive applications on the half-ton 1980 Ford, 1988 Chevy and GMC, and 2002 Dodge pickups.
There also were several outliers with independent rear suspensions: Those included the classic rear-drive Forward Control Corvair and Volkswagen Type 2 pickups based on vans, the eye-catching all-wheel-drive Honda Ridgeline and the military-based four-wheel-drive original Hummer H1. But what about today's pickup trucks?
Suspension basics haven't changed much in many respects; manufacturers have focused on refining proven designs. NASCAR uses a similar approach: A stock car's rear suspension is essentially a heavily engineered, adjustable version of what you'll find under a 45-year-old GM pickup.
Rear Axles
With one midsize exception, the Ridgeline, every pickup sold in the U.S. uses a solid rear axle, meaning the outer axle tubes are locked to the center differential. Inside, axle shafts transfer rotational forces from the differential to the wheel hubs. This type of axle setup is reliable, serviceable, cost-effective and good for varying loads because wheel alignment doesn't change with load. In most cases, a leaf-spring suspension is used to locate the up-and-down forces on rear axles for similar reasons. Although it's a simple design, it can be hard to tune because the springs must carry weight as well as locate the axle longitudinally and laterally while controlling axle rotation and keeping the pinion angle within specifications. On some Jeeps and mid-1990s GM ZR2 pickups, a Panhard rod (aka, a track bar) was used with live axles and leaf springs to control excessive lateral axle movements.
Ram currently uses coil springs on its 1500 and 2500 rear axles, so the spring has to carry only the weight of the truck and bed load. Since a coil spring isn't a series of metal (or composite) strips rubbing against each other like a leaf spring, its movements cause less friction. This delegates axle location and rotational control to other suspension connections, typically called links, arms or radius rods used for longitudinal location, and a Panhard rod or Watts linkage (last seen on 2003-2009 Dodge Durango and Aspen SUVs) for lateral control. All pickups with independent rear suspensions use air or coil springs; most pickups with live axles use leaf springs (exception is the Ram 2500).
Air springs or airbags, optional on Ram 1500s, add complexity but also provide other benefits not found in any other configuration. They are height adjustable for ground clearance, entry ease and aerodynamics, and can level a load or trailer, which provides more consistent steering and handling, and requires less headlight adjusting. To its credit, Ram is the only heavy-duty pickup manufacturer to offer a dedicated rear air suspension system on the 2500 and as supplemental springs on 3500 dualie models.
Front Suspensions
Up front every half-ton and midsize pickup uses an independent suspension for ride quality, steering precision and in some cases, crash deformation characteristics. That's because independent front suspensions provide manufacturers with more options for steering box and shaft placement. Independent front suspensions are the only type on GM HDs. In this type of suspension, each wheel moves on its own for singular control; without a heavy, solid tube joining the wheels there's far less weight to control. Coil springs are quite prevalent on most pickups' front ends, though torsion bars (thick anti-roll bars running front to back) have been used. Currently they can be found on Chevy and GMC HD pickups.
Shock Absorbers
Shock absorbers attached to the axle and frame help control spring movement. Shock absorbers are literally meant to absorb any shock inputs the front or rear axle might encounter. Many independent front-end designs use "coil-over" shocks in which the springs are coiled around the shock are combined to save space and provide better steering precision; however, they are not ideal for carrying heavy loads.
Shocks absorbers come in many different designs: monotube, twin tube, remote reservoir, even magnetic. Monotube shocks — called that because the damping and gases are all within one tube — can be mounted right side up or upside down. This can be an advantage if you are particular about removing as much mass possible from moving parts. There's also some leeway in where shocks are mounted on leaf-sprung rear suspensions: staggered (one ahead of the axle, one behind), outboard or inboard of frame rails, etc. Mounting decisions affect how a vehicle handles with and without a load or when off-road.
Remote-reservoir shocks (used in the Ford Raptor and Toyota TRD Pro models) allow for better cooling of the shock fluid, providing improved, consistent shock performance. An overheated shock absorber will lose some, if not all, of its ability to control harsh or repeated hits.
One of the most advanced shock systems is the fast-acting Magnetic Ride Control shocks on GM pickups such as the GMC Sierra Denali. They change the viscosity of the internal fluid many times per second via electrical input for maximum control and flexibility in a wide range of situations, much wider and quicker than a normal shock can accommodate. Shock absorbers also can be used as steering stabilizers mounted laterally between a big truck's steering arm and a fixed point under the truck, and to damp axle rotation on a live axle, such as Ram's Power Wagon's rear suspension.
Body Roll
Another issue to understand when considering how a big truck's suspension works is body roll, or how a vehicle can handle the forces that want to tip it over when taking a curve or corner at speed. Body roll usually is controlled by laterally-oriented steel anti-roll bars (some are actually tubes) that resist twisting when rotated; they keep the truck flatter during turns at speed.
Virtually every pickup has one on the front, and many have one on the rear as well. In fact, you can add larger diameter bars at both ends if you're uncomfortable with the lean you experience, or just to the rear to help with heavier loads such as a heavy bed camper. But remember that will change the balance of the truck when it rides empty. On the current-generation Power Wagon (based on a three-quarter-ton chassis and biased for serious four-wheel-drive trails), the front sway bar can be electronically disconnected to allow maximum wheel travel to better flex over rocky or uneven terrain. Above a certain speed, the sway bar will automatically reconnect to provide a stiffer, more controlled front-end feel.
What About the Future?
In the future, unique suspension systems used today likely will find wider acceptance and offer better control and more flexibility. We expect more air suspension options and magnetic ride technology to provide better fuel economy, load-carrying capability, comfort and handling. It wouldn't surprise us if the computer systems on new vehicles will be better able to predict what's likely to happen next on the road, possibly leaning into a turn at the first steering input to make a big truck feel more like midsize car.
Active anti-roll-bar systems already found in Range Rover SUVs, luxury sedans, and Toyota's and Lexus' active suspensions could improve highway and trail performance for small and large pickups. The Toyota 4Runner SUV's cross-linked shock system is an impressive active suspension system that works as well in four-wheel drive as it does when entering a 240-degree curving freeway on-ramp.
We also predict that as sales of luxury-model pickups increase, we'll be more likely to see more canyon-carving trucks with independent rear suspensions. The new 2017 Ridgeline will have coil rear springs and an IRS, and is anticipated to have a payload of 1,600 pounds; likewise, the 2016 Mercedes-Benz Metris midsize commercial van (also with coil springs and IRS) has a minimum payload rating of 1,800 pounds, more than many half-ton pickups.
Bushing technology also is likely to improve, perhaps adding a self-adjusting or computer-controlled aspect to them, allowing them to quiet engine vibration or wheel chatter while allowing precise steering. Less vibration means quieter and less-stressed parts and pieces.
And we expect broader application of magnet ride systems, perhaps even grouped with towing packages where damper behavior would be modified simply by engaging Tow/Haul mode or when sensing heavier loads.
Front suspensions may adopt a dual ball-joint lower coupling and have been used on everything from VW Passats to BMW SUVs and the new Lexus LS. This arrangement pays big dividends in bump absorption, handling and directional stability, and leaves more room for axle shafts and bigger brakes to move freely and stay cool.
Further down the road, we expect tuning of active suspension pieces like air springs, self-adjusting shocks or active anti-roll bars to link with cameras and navigation data to prime the suspension before it hits a bump or comes to a sharp bend, making the suspension more predictive than reactive. No matter what happens, we're confident we'll be getting more sophisticated and smarter suspensions to keep our pickups under control.
Manufacturer Images
2015 Ram 2500 rear airbag and multi-link suspension, compressor, and air tank (above)
2015 Ram 1500 rear air suspension and monotube shocks
2015 Ram Power Wagon front swaybar disconnect
2015 Honda Pilot rear independent suspension
