Best Off-Road Suspension For Your 4WD Truck – A Complete Guide

1 How Does A 4×4 Off-Road Suspension System Work?

Similar to an on-road car, the function of an off-road suspension is to smoothen the bumps and keep the tires in contact with the road to ensure better vehicle control. They have similar construction and function, just like the suspensions on your passenger car. The spring absorbs the energy transmitted by the wheels as they go over bumps, and the shock absorber or dampers minimize the vibrations. Both spring and shock absorbers work together on off-road vehicles as well, but they have unique characteristics designed to meet the requirements of an off-road vehicle. The two common springs used are coil springs and leaf springs. Just like other vehicles, the front suspension of an off-road vehicle is more complex because it absorbs more braking torque and has to accommodate for the wheels to turn left and right. However, there are some key differences between off-road and road-car suspension.

The front suspension of a truck or an off-road vehicle is more complicated for two reasons. First, off-road vehicles have bigger wheels that allow them to tackle rough roads and broken terrains easily. Second, most four-wheel-drive vehicles and SUVs feature a solid axle with leaf springs. Such a suspension is called a dependent system because the two wheels are connected with an axle, making them a single unit. Unlike passenger cars that are driven mostly on-road and use MacPherson struts, off-road vehicles have a different ‌suspension system. These include solid axle with coil springs, solid axle with leaf springs, independent front suspensions (IFS), twin-traction beams (TTB) suspension, etc. On the rear, most 4×4 vehicles are equipped with a solid axle with leaf or coil springs.

2 What Are Different Types Of Off-Road Suspensions?

The technology behind off-road suspensions has evolved with time and allowed off-road enthusiasts to tackle tough terrains easily. To meet the growing needs of drivers, off-road suspension kits are constantly revamped and improved with new innovations. Different types of suspensions are available today that are designed for specific terrains and conditions. It is necessary to understand the types of off-road suspensions, their design, and how they perform.

Solid Axle or Rigid Axle Suspension (Dependent Suspension)

Solid axle suspension, also known as beam axle, live axle, or rigid axle suspension, is the most common type used on off-road vehicles. This is a dependent suspension system because both the wheels and suspensions are connected by a solid axle housing. If one wheel moves up or down, it will affect the wheel on the other side. A solid axle suspension features an axle that runs from one wheel to the other and moves up and down with the wheels. They also feature leaf springs that run parallel to the vehicle’s frame and are attached to the axle. In some vehicles, coil springs are used and some rare vehicles use a combination of both leaf and coil springs.

The leaf spring is mounted to a solid perch on one end and the shackle on the other end. When the wheel hits a bump, the leaf spring compresses and becomes flatter and longer. The shackle on the other end allows the spring to move without binding. Although coil springs are also used with solid axle suspensions, leaf springs are more favorable because of their progressive spring rate. The spring rate is the force required to compress the spring to a particular length. A higher spring rate leads to a stiffer ride and a lower spring rate offers a softer ride but increases the body roll. The leaf spring suspension can be tuned by changing the length, arc, thickness, and number of leaves to carry different loads and can be used for various applications. Leaf springs need space and can be seen mostly on larger trucks that have a lot of space. Therefore, small trucks and SUVs rarely use leaf springs and are equipped with independent suspensions.

Advantages Of Solid Axle Suspensions

• Solid axle suspension is very durable, dependable, and lasts a long time, making them favorable for off-road trucks.
• They offer good balance while driving on uneven surfaces because the axle works as a single unit and if one wheel goes down, the wheel on the opposite end comes up. This also prevents your vehicle from rolling over on extreme terrains.
• This setup comprises fewer moving parts, which makes the construction less complicated and ensures maximum torque transfer to the wheels.

Disadvantages Of Solid Axle Suspensions

• Solid axle suspensions are heavier compared to independent or coil-over-shock suspensions.
• Due to their design, solid-axle suspensions decrease the ground clearance of the vehicle. If ground clearance is something you cannot compromise on, then solid axle suspensions are not favorable.
• A solid axle suspension offers a bumpy sensation and vibration in the vehicle’s cabin. This makes the ride rough and hard to control.

Independent Front Suspensions (IFS)

Unlike dependent suspension systems, where two tires are connected by an axle, in an independent suspension, both are unlinked and operate independently. This system allows each wheel to move freely without affecting the wheel on the other side of the axle. In other words, if one wheel hits a bump, the other wheel stays undisturbed. Modern vehicles today are equipped with independent front suspensions (IFS) and they are also used on the rear axle of the vehicle. The most common setup of an independent suspension system uses A-arms, also known as control arms. These arms are perpendicular to the frame and attached to both sides of the vehicle via rubber bushings, allowing the wheels to move independently from each other.

The two most common types of independent suspensions used today are MacPherson strut and Double Wishbone suspensions. MacPherson struts are widely used on front-wheel-drive passenger cars. It has a simple construction with one lower arm and plays an important role in providing structural support and holding the wheels in an aligned position. A double-wishbone suspension features two control arms (upper and lower) with the upper control arm usually shorter than the lower. This suspension features a shock absorber and coil spring assembly that is mounted on control arms. Furthermore, these control arms are adjusted to change the caster, camber, toe, etc. to align the wheels of the vehicle and improve its handling.

Advantages Of Independent Suspensions

• The independent movement of wheels is beneficial on extremely rough and rocky terrains.
• With the absence of axle housing, like dependent suspensions, the vehicle has a higher ground clearance and can tackle huge obstacles easily. Intensive off-roading like rolling over steep hills and boulders is un-challenging with independent suspensions.
• Since each wheel is isolated from the other wheels, all tires are in proper contact with the road, offering excellent traction. This allows maximum traction and a smooth ride over bumps.

Disadvantages Of Independent Suspensions

• These suspensions are not as durable and reliable as solid axle suspensions. They are prone to more breakdowns and mechanical problems, leading to increased repairs and costs.
• An independent suspension system also uses more moving parts and features a complicated setup.
• It is more expensive compared to a solid axle suspension system.

Twin Traction Beam (TTB) Suspensions

The Twin Traction Beam (TTB) suspension system was a revolutionary design released by Ford, which uses both independent and dependent suspensions. This suspension system uses two beams at the front, with one end mounted to the pivot and the other to the wheel. A U joint at the center allows independent movement of the beams that act like long control arms. Initially, twin traction beams or Ford’s Twin Beam suspensions were released in two variants: I-Beam for two-wheel-drive vehicles and Twin Traction Beam for four-wheel-drive vehicles. They feature coil springs and can offer over 30 inches of suspension travel or more. This suspension system offers the best of both solid axle and independent suspensions because it can handle heavy loads and handle great on roads.

Advantages Of Twin Beam Suspensions

• Twin beam suspensions offer huge amounts of suspension travel at a lesser cost, making them a favorite amongst high-speed desert racers that participate in events like Baja1000.
• Due to the long length, the twin beams are very strong and they spread out the stresses and have a better shock ratio compared to control arms (A-arms).

Disadvantages Of Twin Beam Suspensions

• The beams pivot at the center, which makes the wheels swing along an arc, causing the camber to change.
• Apart from an unstable camber, this suspension setup also leads to uneven tire wear.

Four Link Suspension

Some solid-axle suspension systems use coil springs instead of leaf springs because they are more compact and do not support the axle like leaf springs. Therefore, a radius arm design is used where the arm runs parallel to the frame and is perched on the frame at one end and mounted to the axle housing on the other. This allows the axle housing to pivot up and down. Additionally, a track bar, also known as a Panhard Bar, running perpendicular to the radius arms keeps the axle centered on the frame. This suspension system was widely used by Ford and Dodge Ram trucks.

A parallel four-link suspension is a variation of a radius arm suspension. Instead of a fixed mount used on the radius arm suspension, the four-link system uses an upper and lower link on each side with pivots on both ends. It also uses coil springs and a track bar to center the axle, just like radius suspensions. As the axle moves up and down on rough roads, the links keep the caster angle constant. While using a parallel four-link suspension system, a Panhard bar is needed to locate the axle side to side. This track bar is eliminated on a newer version called Triangulated four-link design in which the upper bars are placed at an angle and when connected to the axle and the frame, they form a triangle. This keeps the rear axle centered under the vehicle and there is no need for a separate lateral locating device like a Panhard bar.

This type of suspension system offers you a choice of choosing between different kinds of shock and spring combos suited for many terrains. With the right knowledge on how to tune your suspension system, you can adjust the length of links, their angle, and how the vehicle reacts to acceleration, braking, turning, and high-speed and low-speed performance. Even the most extraordinary trucks on the planet called Trophy Trucks, which are designed to exceed 200kmph in deserts, use a similar four-link solid axle suspension design. The trophy truck suspensions feature trailing arms that attach low on the chassis in the front and below the axle housing at the rear, offering over 35-40 inches of suspension travel. This design keeps the tires on the ground as much as possible for traction and maximum driver control.

Suspension Kits And Body Lift Kits

Off-road kits are great for modifying your stock suspensions and help you raise the body and frame of the vehicle to create additional ground clearance. This allows you to make room for larger tires and bigger suspensions for more suspension travel. Several manufacturers make lift kits and suspension lift systems, specifically for this purpose. However, before choosing a suspension lift kit, it is essential to understand what a lift kit is and how it works. DIfferent suspension kits are designed for different purposes. For example, a high-speed desert vehicle and a rock crawler have entirely different suspension setups.

There are two types of lift kits: suspension lift kits and body lift kits. Suspension lifts include shock absorbers, sway bars, springs, and other components that can help you improve the suspensions of your truck or SUV. Most trucks and SUVs have a body-over-frame construction. The suspension lift kits raise the vehicle’s body and frame above the wheels, increasing the distance between the axle and the chassis. Installing a suspension lift on your 4×4 truck requires expertise to ensure handling, braking and steering do not get compromised.

Body lift kits are a comparatively simple way to modify your vehicle and increase its height. They use a system of blocks or spacers that allow you to raise the vehicle’s body above the frame. This is a simple modification that does not change the power train and core suspension components. As a result, the body lift kits cost less and require less installation expertise compared to suspension lift kits. Lift kits are a great way to make your vehicle more functional and add wider and bigger wheels.

Coil Spring Vs Leaf Spring Suspensions

VA combination of leaf springs and solid axles is very common in trucks and comes as a standard from the manufacturer due to its durability and simple construction. They are usually made from spring steel and stacked together with varying lengths for different terrains and loads. A stock leaf spring offers a decent ride under normal driving conditions. However, they can be replaced with an aftermarket high-quality leaf spring to haul loads or off-roading. They are sturdier than coil springs and handle heavy loads easily. Leaf springs can also be raised or lowered easily according to your requirements. Coil springs, on the other hand, are used on independent suspension systems and mostly on radius arm or twin-traction beam suspensions. Coil springs are costly compared to leaf springs and are not usually preferred for heavy vehicles. However, they are used a lot in high-performance applications like off-road racing, rock crawling, etc. as they offer a wide range of suspension movement.

Leaf Springs	Coil Springs
Strong and simple construction and does not require linkages.	Coil spring offers more range and increased suspension travel.
Leaf springs support the chassis of vehicles, making it ideal for heavy and commercial vehicles to carry huge loads and cargo.	Offers safe, improved ride quality and reduced bounce on rough terrains, making the ride quieter and smooth.
Costs less compared to coil springs and has long-lasting and enduring capabilities.	Coil springs are light and offer increased ground clearance for better off-roading capabilities.
Over time, leaf springs lose their shape, and sag, and alter the cross weight of the vehicle, affecting the handling.	Coil springs do not make sounds as they get old, require less maintenance compared to leaf springs and you don’t have to lubricate the springs.
Leaf springs offer less suspension travel and range compared to coil springs.	Coil springs are not suited for heavy vehicles as they can crack or break under excessive pressure.

3 5 Most Important Factors To Consider While Choosing An Off-Road Suspension

There are several types of off-road suspension to choose from, but meeting your off-roading requirements is very important. If you are a hardcore off-roader who likes to tackle tough terrains and like to participate in events like rock crawling, then you should invest in a complete suspension system. However, if you do light off-roading and are seeking a good balance between street riding and broken roads, an aftermarket suspension lift kit or minor modifications with less technicality will do enough. To ensure you choose the correct suspension for your 4×4 truck, consider the factors mentioned below.

Weight Capacity

The weight capacity of a suspension determines how well it can handle the load of the vehicle and other components. A 4×4 off-road truck can have several accessories and components like bullbars, rear bumper bars, auxiliary fuel tanks, roof racks, fridges, etc. Ensure the suspension system you are purchasing is rated for that weight capacity. It is also known as Load Rating and is the continuous weight that your suspensions are designed to carry. Usually, the springs of a suspension system are designed for a specific load. Under heavy load and wrong spring rating, the suspension can bottom out or can lead to a very stiff and rough ride, making the ride uncomfortable and challenging on rough terrains. Since the suspension system plays a vital role in the vehicle’s handling, it’s necessary to consider these factors while choosing one for your car.

4WD Flex Or Axle Articulation

4WD flex or axle articulation is the vertical wheel travel and how far the axle can move in relation to the chassis. Articulation helps you keep all four wheels on the ground to ensure better stability and traction. A generous amount of flex will help you get your 4×4 truck out from a rut easily without causing your vehicle to tip over. When choosing a suspension for your 4WD vehicle, you must consider the flex or axle articulation depending on your off-roading requirements. A suspension system with longer control arms, longer shocks, and sway bar disconnects can help you achieve better articulation. The coil spring compression rate is a determining factor for better articulation. A vehicle’s 4WD flex can be measured by a Ramp Travel Index (RTI) score. Usually, a ramp at an angle of approximately 20 degrees is used on which one tire of the vehicle is driven up until the opposite tire starts to lift off. A greater RTI score means more axle articulation and increased flex, making the vehicle suitable for extreme off-road.

Durability

The durability of the suspension system is an essential factor to consider while selecting one for your vehicle. Since these suspensions are designed to operate in tough conditions and broken roads, they should be durable enough to last a long time. The life and performance of suspensions can vary depending on your driving style and terrain. High-speed desert racing can cause your suspensions to heat up as they are worked hard. A rock crawler or extreme off-roading vehicle might not witness heated suspensions, but they must be tough and durable to withstand extreme axle articulation, rocks, and boulders. Choosing the correct suspension system for your 4×4 vehicle is vital to ensure it meets your driving requirements.

Size Of Tires

Tire size is an important factor in determining which suspension is best for your 4×4 vehicle. Larger tires are very helpful in driving over large obstacles without getting stuck, but they require stronger suspensions to complement the required height and strength. Some people use larger tires solely for aesthetics and do not intend to drive off roads. If you are using up to 33 inches of tires, you can use a solid axle and leaf spring suspension setup. You can also use a simple body leveling kit or body lift kit without affecting the handling of the truck significantly. However, with tires up to 35 or 37 inches, you will have to upgrade your suspensions with coil spring shock absorbers and track bars. Using bigger wheels will also increase your ground clearance and throw the vehicle’s center-of-gravity off-balance. This requires a certain level of expertise and proper suspension selection. You might also have to change your drive shafts and steering system which makes this a heavy upgrade.

Comfort And Terrain

The final factor to consider while choosing a 4×4 suspension system is comfort and overall driving experience. The function of a suspension system is to prevent vibrations, noise, and harshness from reaching into the cabin and provide a comfortable driving experience. Before selecting a suspension system for your truck, decide the terrain you will drive on. If you commute daily on the road with some rough patches, you won’t need to purchase an expensive suspension upgrade. However, for rough tracks, occasional jungle camping trips, or off-roading events, you will require a suspension system that can handle the task well. The ultimate idea is to choose a perfect balance between comfort and terrains because you cannot achieve maximum comfort and maximum off-road capabilities from a single suspension system. A balanced level of comfort and driveability is the perfect option while choosing suspensions for your 4×4 truck.

4 What Is A 4WD Air Bag Suspension?

An air bag suspension uses compressed air instead of conventional steel springs  for a smooth ride. It is usually powered by an electric pump or compressor that forces air into the air bellows that act like springs. These bellows or rubber bags are made from polyurethane or textile-reinforced rubber. The complete system is known as Electronically Controlled Air Suspension System (ECAS) which consists of various components like vulcanized rubber air springs, a compressed air storage tank, valve blocks to direct air to all the springs, air pipes, and an ECAS computer that controls the amount of air pressure. Two types of airbag suspensions are used: sleeve-type and bellows-type. Bellows style air bag suspensions are very popular and are offered in single, dual, and triple chamber designs.

A major advantage of using an airbag suspension system is its quiet operation and smoother ride compared to metal springs. The cushion of compressed air eliminates direct metal-to-metal contact and offers a plush and comfortable riding experience. The modern air bag suspension system also features a height-control system with height sensors that allow you to increase and decrease the height of the suspension system according to your requirements. However, this system takes up a lot of space and is very complex, making it difficult to install. Furthermore, it’s not very reliable, unless it is a high-quality suspension system, making it an expensive upgrade. 

Upgrading the suspensions of your 4WD vehicle is very crucial to improving its off-roading performance and capabilities. Amongst several suspensions and setups to choose from, the debate between independent versus solid axle suspensions remains unsettled. Both designs are very capable of off-roading with their advantages and disadvantages. The solid axle suspension might not provide the best ride but is very durable and twin-beam suspensions are a perfect and low-cost replacement for your A-arm suspensions with more suspension travel on challenging terrains. If you are not into extreme off-roading and need a simpler mod, you can use off-road suspension lift kits or body lift kits, which will allow you to use wider tires. Ultimately, to choose the correct off-road suspension for your truck, you should understand its use, capabilities, and requirements. This article helps you understand these factors and their role in performance in vehicle safety as well.