Tow-vehicle undercarriage upgrades to improve ride, handling and trailering stability
Suspension art and science involves achieving the best blend of comfort and control. Since comfort is subjective and towing situations are seldom the same for any two vehicles, truck owners often have to compromise. The floating-on-a-cloud “Cadillac” ride comes at the expense of cornering stability and body-roll control. On the other “ride” of the coin, a stiff suspension can increase handling predictability and raise towing and hauling capacity — while annoyingly jiggling and jarring in-cab occupants over uneven surfaces. “Throw a couple more leaf springs in there, George. They’re complaining up in Utah again” doesn’t cut it as “engineering” anymore.
Automaker engineers prioritize the most-common situations, particularly when designing pickup suspensions: half-ton models tend to be considered commuter vehicles with mostly empty beds; heavier trucks have stiffer suspensions with greater towing and payload capacities but less-supple ride quality. The aftermarket products here can help trailer and slide-in camper owners fine-tune their tow vehicles’ ride and handling.
Shocks
Shocks’ primary function is controlling the truck’s unsprung weight: tires, wheels and solid axles. Many automakers use cost-effective twin-tube shocks. Optional equipment such as towing packages and higher-end trim levels often include upgraded monotube shocks from manufacturers such as Bilstein or Fox. Regardless of style, modern shocks generally have velocity-sensitive damping: the faster the suspension moves, the stiffer the damping resistance. In addition to controlling bounce, shocks also regulate sway during steering as well as dive and squat resulting from braking and acceleration.
Twin-Tube: This style of shock houses the piston in an inner chamber while oil resides in an outer tube. More-refined “gas-charged” models add high-pressure nitrogen to the fluid chamber to combat heat-induced foaming — damping suffers as the shock oil aerates (known as “shock fade”).
Ride firmness is regulated by fluid flow. When the pistons’ valves let fluid flow more freely, the truck’s ride is softer and handling is less precise. The faster the suspension cycles, the less fluid is allowed to flow, stiffening the ride for better handling.
Gas-charging allows additional sensitivity to be added in select twin-tube designs. Position-
sensitive damping can employ tapered grooves in the piston chamber to further control fluid flow. A “comfort” zone is identified in the range of normal piston travel, and control zones are created at the more extreme ends of compression and rebound to limit flow and stiffen the ride. Acceleration-sensitive damping uses a compression valve, which opens to increase fluid resistance during impacts (potholes and such). Oil seals on twin-tube shocks eventually fail, effectively ending their service lives.
Monotube: This style contains fluid and nitrogen gas in a pressure chamber, which also houses a working piston and a dividing piston. Many monotube manufacturers use aluminum for the shock bodies to help dissipate heat, and remote-reservoir options are also common to further limit fluid temperature by increasing oil capacity and surface area. Monotubes can be mounted shaft up or shaft down. This design also accommodates coil-over shocks/springs and struts, which basically delete the upper control arm and regulate both sprung and unsprung weight in independent suspension systems.
Adjustable Bypass: Possibly overkill for many towing applications, these race-bred shocks offer even more flexibility. They are typically rebuildable, allowing lifetime service. Also, position-sensitive adjustable bypasses allow rebound and compression to be tuned separately for a wide range of ride refinement. Internal-bypass models are the most suitable for OEM upgrades; race-style units attach external tubes to the main shock bodies, and the resulting increased girth presents more mounting challenges.
Anti-Sway Bars
Just as shocks are a doable DIY upgrade, stiffer anti-sway bars are a tow improver that can generally be installed at home. Their primary benefit is controlling side-to-side weight transfer while towing and hauling, especially during cornering and also while changing lanes and experiencing sideways wind gusts at highway speeds. An anti-sway bar, more accurately known as an anti-roll bar, is especially useful on a truck hauling a top-heavy slide-in camper.
Vibration-Absorbing Rubber Shackles
For trucks with rear leaf springs, aftermarket shackle-replacement kits are available that use internal rubber “springs” to absorb the off-the-line acceleration jolt that can happen if you stick your foot in it too far, exacerbated by towing. These direct-replacement systems also help disperse the energy resulting from axle movement over road-surface irregularities.
Overload Springs
Also for leaf-spring suspensions, these kits add a semi-elliptical leaf to increase the spring rate (amount of force needed to compress the spring pack). Many prominent aftermarket suspension companies offer add-a-leaf kits. These require disassembling the existing leaf pack (which can sometimes be accomplished with the springs still on the vehicle), inserting the add-a-leaf, then reassembling the pack. “Helper” spring kits install on top of the existing leaf pack. Note that none of these approaches claims to increase vehicle weight ratings or capacities.
Airbags
Airbags (and solid-material “rubber springs”) also function as helper springs. They are particularly useful for leveling trucks while towing. Most prominent manufacturers offer both rear-only and four-corner airbag systems.
Adding airbags requires wiring in an electric air compressor and plumbing pneumatic lines from the compressor to the storage tank and the bags. Some truck owners use this opportunity to upgrade the onboard air capacity for additional functions such as service air for inflating tires, adding air horns, powering pneumatic tools and actuating air-selectable differentials such as the ARB Air Locker.
Base airbag kits allow the rubber bellows to be manually inflated and deflated, similar to tires, by way of installing air-fill lines and air chucks at convenient locations on the truck. More convenient and at added expense are systems that permit inflation control from the cab or remotely from an app-based system.
Fortunately, trailer owners have many options for upgrading their tow rigs’ suspension systems. The products shown here present a cross-section of the possibilities, ranging from straightforward replacement components to more complex systems.
aFe Power|
aFe offers a variety of Sway-a-Way monotube shocks. Top of the line are external triple-bypass models with remote reservoirs, targeted primarily to vehicles that spend time in the dirt. These shocks offer externally adjustable, position-sensitive damping: two compression settings and one rebound adjuster.
Air Lift|
Air Lift’s LoadLifter line of Goodyear-engineered air springs is designed to clear fifth-wheel hitch framework. Internal jounce bumpers are included to absorb shock, even when the bags are totally deflated. Installation is designed as bolt-on, and systems are available that offer up to 7,500 pounds of load-leveling capacity, thanks to 7-inch-diameter double-bellows bags.
For remote airbag control, Air Lift offers the WirelessAir system. Combined with the company’s compressor, the system allows pressure to be individually controlled to each bag from the remote unit. A smart-phone app is available for remote monitoring and control.
Bilstein|
Upgraded shocks are a common first step to improving towing control. Bilstein monotubes are premium original equipment offerings in some applications. The company’s aftermarket line of shocks and struts includes zinc-plated bodies for improved corrosion resistance.
Daystar|
Daystar offers an Air Bag Cradle kit that is designed to increase suspension travel in trucks
having 6-inch-diameter bellows-style rear airbags. The system uses polyurethane lower mounts and is engineered to restore up to 20 percent of the suspension travel that Daystar claims can be lost when installing airbags.
Energy Suspension|
Polyurethane chassis bushings like those from Energy Suspension can provide more predictable handling and flatter cornering compared to factory rubber bushings. Polyurethane also lasts longer because it resists degradation from oil and grime better than rubber. Most polyurethane manufacturers also offer stand-alone component kits for anti-sway bars, springs and even powertrain mounts.
Firestone|
The Ride-Rite line of airbag systems from Firestone offers leveling assistance and supports up to 7,500 pounds. Two- and four-bag kits are available with a variety of options and upgrades.
Wireless in-cab airbag control systems are easier to install than traditional kits, which 
require running lines into the passenger compartment. This Air Command 3 system from Firestone Ride-Rite is one popular example.
Fox|
Fox is a prominent manufacturer of adjustable monotube shocks. Its 2.5 line (with 2.5-inch shock body diameters) offers customers premium features such as remote reservoirs and compression-adjustment knobs.
Hellwig|
Hellwig’s Big Wig airbag line is engineered to assist load-leveling capacity at the lowest-possible air pressures. The underlying goal is a softer ride without compromising load leveling and support.
Hellwig BigWig anti-sway bars are available as front and rear upgrades for popular trucks. They use larger-diameter steel than factory bars to improve stability, particularly when towing or hauling a camper.
Kelderman|
Kelderman, best known for air-suspension systems for lifted vehicles (extreme Ram kit shown), offers stock-height kits for light- and medium-duty trucks, ranging from 1500- to 5500-series vehicles. Kelderman two-stage systems are designed to improve ride in leaf-sprung trucks by replacing the shackle hanger with moving air-suspension framework. Kelderman also offers rear four-link systems for popular three-quarter- and one-ton trucks.
King|
A prominent manufacturer of racing and coil-over shocks and air-bump stops, King offers a line of 2.5-inch-diameter OE replacement dampers for popular trucks. Features include compression-adjustment knobs, offering 16 positive clicks of ride-firmness choices.
Level Ride|
In-cab airbag controllers are a convenient upgrade over manually inflating/deflating bags at their bellows. The Level Ride system uses 
pressure and height sensors, plus monitors battery voltage. The Bluetooth- enabled controller allows touchscreen and voice control. Designed to self-level the vehicle, it can save and store three different height presets.
MaxTrac|
Towing primarily taxes the rear suspension. Components such as MaxTrac Leveling Keys for late-model Chevy/GMC HD IFS trucks are available for front leveling. These forged keys are advertised as 25 percent stronger than the OE cast units and offer 1 to 3 inches of adjustable front lift. Shock extender brackets (not shown) are included in the kit.
MORryde|
The MORryde RS system is a shackle-replacement upgrade for vehicles with rear leaf-spring suspensions. It uses rubber springs to isolate and absorb road shock and is marketed as a cost-effective alternative to airbags. The company claims the system can be easily installed onto most trucks and specialty vehicles.
Pacbrake|
Pacbrake offers a wide line of airbag systems and related components for popular trucks. Pacbrake’s Amp line of pneumatic controls includes the WirelessAir system to remotely adjust air-spring pressure. Features include military-grade solenoids, a ¼-horsepower 12-volt DC compressor, a preassembled control board and a plug-and-play harnesses.
Rancho|
The adjustable Rancho RS9000XL is a flexible shock-upgrade option. This gas-pressure, multitube shock allows the user to dial in a choice of nine valving settings. Lower levels allow freer fluid flow for a softer, factory-type ride. Middle levels provide increased stiffness and control, and the highest levels are firm for towing and higher-speed stability.
Roadmaster Active Suspension|
The Roadmaster Active Suspension kit is designed to control axle wrap and wheel hop in leaf-spring suspensions. The system is also engineered to add towing strength without increasing ride harshness.
Roadmaster Suspension Solutions|
Known for the Comfort Ride line of trailer shocks and slipper springs, Roadmaster Suspension Solutions offers RSS Anti-Sway Bars for late-model full-size tow vehicles. The chromoly-steel bars are designed to significantly improve handling and side-to-side stability, especially when cornering. They also help keep tow vehicles level through crosswinds.
Sulastic|
Sulastic was one of the first manufacturers of rubber-spring replacement shackles. The bolt-on system adds a third pivot point to help absorb suspension jolts and control pickup-bed bouncing.
SuperSprings|
SuperSprings suspension stabilizing systems are designed to help stabilize and level rear leaf springs without adversely affecting ride quality. Preload tension can be adjusted by using different hole locations in the kit’s shackles.
SuperSprings’ SumoSprings are a solid-polyurethane alternative to airbags. They have micro-cellular bubbles that trap air, eliminating the need for an external compressor and plumbing. Progressive rates increase resistance the farther the SumoSpring compresses.
Timbren|
Timbren’s Aeon solid-rubber helper springs are bolt-in rear bump-stop replacements. They are designed to control body roll and prevent the main springs from bottoming out.
Torklift|
StableLoad from Torkliftis designed to preload the factory overload 
leaf. The goal is to improve handling characteristics and braking distances when towing and hauling by reducing sway.
Tuff Country|
Traction bars such as these Tuff Country units for Ram 2500/3500 trucks are designed to 
greatly reduce wheel hop and axle wrap that can result from increased horsepower, towing and larger-than-stock tires. Greaseable and rebuildable heim joints allow the bars
to be adjusted to fit varying ride heights.
SOURCES
Sway-A-Way monotube and bypass
shock absorbers
aFe Power, www.afepower.com
Airbag systems, components
Air Lift Company, www.airliftcompany.com
Monotube shock absorbers
Bilstein, www.bilstein.com
Airbag cradles, polyurethane bushings
Daystar Products, www.daystarweb.com
Leaf-spring overload stabilizer
Dynamic Suspensions
www.dynamicsuspensions.com.au
Polyurethane bushings
Energy Suspension, www.energysuspension.com
Airbag systems, components
Firestone Ride-Rite, www.riderite.com
Monotube shocks
Fox Factory, www.ridefox.com
Airbags, heavy-duty sway bars,
helper springs
Hellwig Products, www.hellwigproducts.com
Air suspensions, four-link conversions
Kelderman, www.kelderman.com
Monotube and bypass shocks absorbers
King Shock Technology, www.kingshocks.com
Front leveling kits
MaxTrac Suspension, www.maxtracsuspension.com
Suspension systems, rubber shackle kits
MORryde International, www.morryde.com
Airbag systems and components
Pacbrake, www.pacbrake.com
Polyurethane bushings
Prothane, www.prothane.com
Premium replacement shock absorbers
Rancho, www.gorancho.com
Leaf-spring helper system
Roadmaster Active Suspension
www.activesuspension.com
Anti-sway bars
Roadmaster Suspension Solutions
www.roadmasterinc.com
Rubber spring shackles
Sulastic, www.sulastic.com
Overload and helper springs
SuperSprings, www.supersprings.com
Composite helper springs
Timbren, www.timbren.com
Leaf-spring stabilizing products
Torklift, www.torklift.com
Tractions bars, suspension components
Tuff Country, www.tuffcountry.com
