Going off-road and riding over sand, mud, snow, riverbeds, rock, gravel and other types of natural terrain can give you an adrenaline rush like no other, which is why many Australians opt to spend their weekends venturing off the beaten trails. But even if you don’t take it to the extreme and prefer a more leisurely drive, your 4×4’s suspension can take a lot of abuse from divots in the ground, hefty loads, fast acceleration that can wear down your stock parts and negatively impact your safety and comfort. Even though stock 4×4 vehicles are made to take a decent beating from rough terrain, installing an aftermarket suspension can go a long way in keeping your ride safer and more comfortable.
What’s the Purpose of a Suspension System?
As you probably already know, a car suspension system serves a pretty straightforward purpose. Just from the term ‘suspension’ itself, you can get an idea that you’re basically raising something from the ground in an attempt to minimise the impact of forces on the ground. For example, if you lay down on the ground, you’ll feel the vibration when people walk by you. Now lay on a mattress that’s just a couple of centimetres high off the ground and you’ll no longer feel those vibrations. Of course, this is oversimplifying what a vehicle suspension system does, but you get the idea.
Your 4×4’s suspension system absorbs vibration, impact forces from the road and gravitation. Suspension systems in the past weren’t really efficient at absorbing all of the aforementioned forces, so some people used padded cushions to reduce their impact on their butts. Not the best solution, but it still provided a more comfortable ride. And while we’ve come a long way from those days and modern-day suspension systems are advanced right off the factory, there’s still room for improvement, which is why aftermarket suspension systems are some of the most sought after 4×4 accessories.
Further, the suspension system ensures the vehicle’s tires are constantly in contact with the driving surface. While technically it’s the tires that are in direct contact with the surface, the layout of the wheels and axle is connected to the vehicle’s suspension. The vibrations, shocks and all other road imperfections are absorbed by the tires and transmitted through the shock absorbers, further reducing the effects of these shock and vibration forces.
The spring mechanism of modern suspensions compensates for irregularities on the driving surface by pushing the wheels and thus, the tires, against it. If the tires get airborne due to a big bump on the road, the suspension system will try to push them down in an attempt to reestablish contact with the ground. So if your vehicle didn’t feature adequate springs, every bump on the driving surface would send it jumping off the ground, and every high-speed turn on a corner would have the inside wheels lifted off the driving surface, which can make your vehicle flip over. With a proper off-road suspension system, however, your vehicle will remain in contact with the surface at all times, since the springs will push the tires towards it.
When you take these two functions, it’s easy to see how a proper suspension system can improve overall performance and safety. By keeping the tires constantly in contact with the ground, you reduce the chances of flipping and rolling over. Further, the suspension system ensures that power to the wheels is transmitted where it’s needed the most, although this is mainly the job of the vehicle’s transmission.
What Parts Are Suspension Systems Comprised Of?
At the most basic level of modern car suspension construction, there are only two basic parts – the springs and dampening mechanisms. Of course, suspension systems may include other parts, such as suspension struts, bushings, etc. but I’ll be discussing the two basic parts so that you get a better understanding of what you’re looking at when shopping for these 4×4 accessories.
There are three types of springs that are used in suspension systems today – coil, leaf and torsion springs. Coil springs are the same type of string that you can find in retractable ball pens, except they’re larger and made of a heavy-duty torsion bar which is coiled around an axis. This type of spring expands and compresses to absorb the wheel’s motion. Leaf springs are the oldest type of all three, and they’re simple and easy to assemble. They’re basically a few layers of metal bound together to form a single spring unit. Although not as popular as coil springs, you’ll find them on heavy-duty trucks and vehicles.
Torsion suspension systems are slightly different than coil and leaf systems. We can’t talk about torsion bars without thinking about the unique ability of some objects to twist, giving them a spring-like ability similar to that of a coil spring. One end of the torsion bar is either mounted or connected to the wishbone, while the other is connected to the vehicle’s frame. The wishbone acts as a lever, and when you come across a bump, the upward movement of the wheel will be transferred to the wishbone, and the wishbone will move the torsion bar. As a result, the torsion bar will be twisted along the axis, resulting in spring action.
While the springs absorb the energy from vibrations and bumps on the road, the dampening mechanism helps dissipate or control the energy in order to prevent the vehicle from bouncing with each bump until all the energy is fully dissipated. If you press an ordinary spring, it will keep bouncing a few times before stopping. This ongoing bouncing action of the spring needs to be controlled in vehicle suspension systems, and that’s the main purpose of suspension struts, shock absorbers and anti-sway bars.
Shock absorbers are parts of the suspension systems responsible for reducing the amount of vibrations you experience on the road, and reducing the springing action of the springs. In other words, they convert kinetic energy into thermal energy that’s dissipated with hydraulic fluids. The best way to look at shock absorbers is as if they were an oil pump located between the frame of your vehicle and the wheels. The upper mount is connected to a piston rod, and the piston rod is connected to a piston that’s connected to a hydraulic fluid-filled tube. The inner part of the hydraulic fluid-tube acts as a pressure chamber while the outer part acts as a reservoir for excess hydraulic fluid.
When you come across a bump, the wheels will transfer the energy to the springs, which will transmit the energy to the upper mount, then the piston rod and all the way down the piston. The piston has small holes all over it that allow small amounts of hydraulic fluid to pass through them with each movement the piston makes inside the pressure tube. This slows down the movement of the piston, as well as the overall spring movement.
Suspension struts are another dampening mechanism that works just like shock absorbers. These parts are in fact shock absorbers that are already mounted inside the coil springs. This type of mechanism helps reduce the impact of spring forces, and provides structural integrity for the suspension.
Lastly, anti-sway bars aren’t a key part of suspension systems, but they do provide extra stability for any moving vehicle by resisting body roll motions. They’re usually cylindrical steel bars that connect the left and right sides of the suspension on the same axle and are used in conjunction with shock absorbers or suspension struts. When there’s suspension movement in one side of the vehicle, the movement is transferred by the anti-sway bar to the opposite as well in order to create a more level ride. This helps reduce the swaying tendency of your 4×4 when turning.