Off-road suspension: what does it mean? Types of suspensions in off-road vehicles   

The automotive market is rapidly evolving, following modern technological solutions and aiming to for full autonomy in the near future. However, in the off-roading reality, it might seem that time follows a wholly different track. This partially civilized sport (we all understand – sand, mud, dirt) still highly values classic solutions that perfectly fit its rugged nature. 

That’s why, for example, off-road vehicles with dependent suspension are very popular here. However, this doesn’t mean that it is the only type of suspension found in off-road vehicles. There are some enthusiasts who prefer more modern constructions, for example, independent and pneumatic suspension systems. Okay, but what’s the difference? 

The most important feature of dependent suspension is the rigid wheels connection via solid axles. This means that the movements of wheels depend on each other. Changing the position of one consistently affects the other. To put it differently, the drivetrain functions as a direct connection between the wheels, creating an integrated system. It has nothing to do with wheel rotation but rather with their movements horizontally or vertically relative to each other. 

Advantages 

Its uncomplicated construction, despite over a century of tradition, is still used today. Thanks to its simplicity, it offers high durability and solidity, as well as ease of repair and service. It also comes with low maintenance costs. But the biggest advantage for many offroad drivers is its ability to be easily modified. It can be lifted, handle heavy loads as well as overload (G-forces) capacities. It is not without reason that they are used in trucks.

Disadvantages 

Vibrations occurring between the wheels affect both of them at the same time. This is one of the reasons for the risk of experiencing death wobble. Additionally, the dependent suspension system is heavy. It increases the car’s weight but also its unsprung mass, resulting in reduced driving comfort and affecting vehicle stability, especially at high speeds.

There are various subtypes within dependent suspension systems. They are categorized based on the type of spring components used: leaf springs or coil springs and a Panhard rod. The first subtype features two rigid axles connected to the leaf springs and is commonly found in older off-road vehicles, typically manufactured until the 1980s or 1990s, such as the Suzuki Samurai, Jeep Wrangler CJ and YJ, or Toyota Land Cruiser series 60. 

Advantages

Leaf spring suspension offers stability on traverses and provides large amount of support between the wheels, axles, and the car’s chassis. Furthermore, basic modifications are cheap and easy, such as adding an extra leaf spring hanger and block.

Disadvantages

Having two pairs of stiff and hard leaf springs limited the suspension flexibility resulting in reduced mobility and less potential for tilting or axle articulation. Consequently, this may result in discomfort when driving fast on gravel or uneven terrains.

The second subtype of dependent suspension uses coil springs and control arms. Coil springs absorb road shocks and maintain vehicle stability. The control arms provide a movable connection between the wheels and the body, improving the vehicle’s steering. Control arms and coil springs work together to control how the wheels move compared to the car’s body. An example of such an off-road vehicle can be the famous Jeep Wrangler JK, the immortal Nissan Patrol, or just Suzuki Jimny.   

Advantages

A flexible spring on a multi-link suspension offers incomparably greater flexibility in suspension operation compared to a leaf spring on solid axle. Thanks to its wide range of compression, such a design translates to significant articulation and greater capability in overcoming off-road obstacles. However, that’s not all, as this type of suspension also provides excellent vehicle handling and traction, and due to its high efficiency in damping vibrations, it also offers a good deal of driving comfort.  

Disadvantages

While coil springs and control arms allow for a certain degree of adjustment and tuning, it is not the simplest of tasks. Achieving the desired balance between ride comfort and handling can be complex and time-consuming. Moreover, performing larger modifications (e.g., lifts above 3.5 inches) requires replacing a greater number of components. This is not only more difficult but also more expensive. It also translates into a higher vehicle price.

An interesting, but increasingly less popular, solution is a mix of two subtypes of dependent suspension. In this example, springs are mounted on the front axle, while leaf springs are mounted on the rear axle. This solution has worked so well that it remains unchanged to this day in the iconic Toyota Land Cruiser 70 series. This is partly thanks to off-road enthusiasts, who have repeatedly requested no changes to a vehicle that performs excellently in rough terrain.

However, modern off-road vehicles typically feature independent front suspension and a solid rear axle with leaf springs.

Advantages

This hybrid achieves an excellent balance between off-road performance, driving comfort and the ability to transport heavy loads at the rear of the car. 

Disadvantages

The combination of independent front suspension and solid axle rear suspension offers a balance between off-road capability and on-road performance. The rear solid axle instead of springs and control arms provides better support for heavy loads. More flexible front offers greater suspension versatility during everyday use.

Another type of suspension is the independent system. Its name comes from the way each wheel operates on the axle. When one the wheel encounters bumps or uneven surfaces, its movements are mostly separate from the other wheels. This means that reactions to the road conditions are independent for each wheel. Thanks to this, driving is much smoother and free from steering wheel jerks. 

Independent suspension built consists of a multi-link system or McPherson struts on both the front and rear axles. It includes a combination of diagonal, transverse, and longitudinal control arms. Longitudinal control arms are the base and act as connectors. The transverse control arm connects the chassis to the steering knuckle and helps to control the side-to-side movement. The diagonal control arm controls the movement of the wheel assembly in both the vertical and lateral directions. Control arms role is to provide full control over the wheel tilting, resulting in excellent grip and precision of such cars, as well as high driving comfort. However, it is characterized by limited wheel travel. This is certainly a minus for off-road vehicles, as it affects the ability to overcome obstacles. 

Other important components include shock absorbers and coil springs. Some vehicle models, instead of standard shocks and springs, have coilovers. Independent suspension is defined by the absence of a solid axle and features a multi-link system (although multi-link system is totally different from that in a solid axle). This allows for adjusting the mounting point of the spring and enabling the vehicle to be raised or lowered. It is commonly believed that independent suspension is great for sports cars, where speed is the most important. Examples of vehicles closer to off-road use with such suspension systems include mostly SUVs, Toyota RAV 4, Jeep Grand Cherokee WK 2, Jeep Cherokee KL, Jeep Renegade, Jeep Compass, Nissan Patrol Y62, Pajero 4, Subaru Forester, Crosstrek, Outback.

Advantages

Firstly, independent suspension enhances handling, providing better traction and stability during cornering. Additionally, it offers a smoother and more comfortable ride by effectively absorbing transverse bumps in the road, such as potholes.

Disadvantages

Independent suspension isn’t a perfect solution for off-road and has some cons. It tends to be more complex and more expensive to maintain. Additionally, the ground clearance is compromised limiting vehicle ability to traverse rough terrain. Furthermore, its load-carrying capacity is reduced, what making it less effective at supporting heavy loads compared to setups with leaf springs, for example.

Between dependent and independent suspension, there are also vehicles that are a hybrid of both. This solution is typical for pick-up trucks, but it’s not exclusive to them. At the front, a simpler version of independent suspension is present. It consists of a control arms and, in the case of off-road vehicles, a coilovers. Passenger cars, such as the Suzuki Vitara, often feature a MacPherson strut instead of a coilover. 

On the rear axle, both types of vehicles commonly employ dependent suspension setups. Off-road vehicles like the RAM DT typically contain coil springs, while pickup trucks, such as the Volkswagen Amarok, often feature leaf springs. Pick-ups are known for their large loading capacity, located at the back of the car, commonly called the bed. Leaf springs construction is cheaper and solid, that’s why they are more commonly used, especially in utility versions of pick-ups like Ford Ranger. In contrast Ford Ranger Raptor designed more for fun than work use coil springs instead. 

Advantages

The combination of independent front suspension and solid axle rear suspension offers a balance between off-road capability and on-road performance, making it suitable for a wide range of driving conditions. The rear solid axle instead of springs and control arms provides better support for heavy loads. 

Disadvantages

Compared to the fully independent suspension setups, the hybrid suspension may have more limited articulation on uneven terrain, affecting off-road performance in certain situations. The solid axle rear suspension may transmit more road vibrations and harshness to the cabin, resulting in a less comfortable ride, especially on rough surfaces.

The final type of suspension system found in off-road vehicles is the air suspension sometimes referred to as pneumatic suspension. This system utilizes special air bags instead of traditional coil springs. These bags are filled with either air or a combination of air and nitrogen under pressure. 

The air bags are often integrated with pneumatic shock absorbers, forming a single unit that serves as an alternative to standard coilovers. This type of suspension allows for even more precise smoothing of the smallest ground irregularities, resulting in higher driving comfort. 

The air bags are inflated by a compressor powered directly from the car creating a self-sufficient system that replenishes the air in real time. This continuous adjustment allows the suspension height to adapt dynamically to additional loads. However, the greatest advantage for all off-road vehicle owners is the ability to manually adjust the vehicle’s height by changing the pressure in the airbag. An example of such a car is the Land Rover Discovery 4 or the latest Defender. 

Advantages

Air suspension ability to adjust the vehicle’s height is a real game changer in off-roading. Increased ground clearance is very useful when it comes to avoiding rocks and ruts or lowering it for improved stability at high speeds or on even surfaces. Furthermore, air suspension can absorb shocks and bumps better than traditional spring systems, offering a smoother ride over rough terrains. 

Disadvantages

Air suspension systems are generally more expensive to install, maintain, and repair than standard suspension systems. Additionally, they are more complex and include air compressors, electronic control and airbags. This complexity can lead to reliability issues, with more potential points of failure. Airbags are more vulnerable to damage from sharp rocks, sticks, and other debris.

In heavy off-roading, the most important thing is the suspension’s ability to handle high articulation which allows for a wide range of movement in the wheels. This include maximizing the flex (compression) and extension (drop) of each wheel independently, ensuring that they maintain contact with the ground even on very uneven terrain. That’s why, when it comes to off-roading in tough conditions, the capability to easily cross rough terrain is more valuable than comfort. So, the most important factors are the car’s adaptability to modifications and its suspension’s ability to adjust its performance to specific conditions. These are precisely the features of dependent suspension with a solid axle and control arms. It is still the unquestioned king of off-roading: see the Jeep Wrangler. 

Why not independent or air suspension for extreme off-roading? These systems are technologically advanced and more complex, which makes them difficult to modify and less practical for navigating tough terrains and offroad competitions. Does this mean they’re no good for off-roading? Not at all. Independent and air suspensions can perform well on moderate off-road trails and provide superior comfort and handling on uneven surfaces. However, making significant modifications requires a lot of effort and involvement, or sometimes it’s completely impossible. 

We’ve already mentioned several times why modifying off-road suspension is important, during discussions about off-road basics and suspension kits. We also talked about what kind of lifts or modifications you can make to specific types of suspension. 

Off-road tourism is a different story. Compared to hard-core off-roading, it’s a whole other world, requiring different setups even though they might overlap at times. 

On long journeys, comfort becomes key. So, for overlanding, vehicles with a mix of springs and shocks or multi-link suspensions at the front and solid axle setups at the back are preferred. This setup not only increases the vehicle’s load capacity but also keeps it stable when carrying extra weight. 

So, civilized off-road vehicles or rugged road cars, often known as SUVs, are the go-to choices here. They offer the greatest driving comfort, especially if you’re mostly hitting public roads. 

Which off-road vehicle and what kind of suspension is best for you? You’ll need to answer that based on how you plan to use it.