Suspension is everything in a 4×4. It’s the mechanism that quite literally holds everything up and impacts everything from the stability of the ride to the amount of lift. But suspension, as with all man-made things, is not immune to the passage of time or the rigours of use. Indeed, passenger vehicles with stock suspension can start showing signs of fatigue or failure after only a few years, particularly if they’ve been used off-road or for heavy load-carrying and towing.
A suspension issue is not something to be overlooked. It could cause your vehicle to fail its MOT and in more extreme cases it could be, quite frankly, unsafe. A failing suspension could lead to an uneven ride height, front or rear sagging and a ride that’s unstable and unsafe. The most common suspension problems will vary depending on the age of your vehicle, but corrosion of parts, leaks and worn or broken springs are all common causes of failure.
Even if your ride is generally ‘OK’ and meeting basic safety requirements though, that doesn’t necessarily mean it’s in good order. You might need to swap out individual components or even replace the suspension system entirely with a suspension upgrade kit manufactured specifically for your vehicle. If you want to keep on top of your suspension health, you’ll want to keep a serious eye on the following components:-
Your shock absorbers are what control the travel and rebound of your suspension and to work, they typically require oil and gas. When left for a few years, oils naturally begin to break down or turn to foam and this will inevitably lead to a reduction in performance. Over time, seals can also split, which allows oil to leak out of the absorbers.
To test your shock absorbers, park your vehicle on level ground and bounce each corner several times before allowing it to settle. Good spring travel should stop in a controlled fashion, usually after no more than one movement cycle. Continued movement is often a sign of shock absorber failure and will need to be looked into.
Leaf springs can last a long time. Indeed, they were popularly used in the 70’s and many of those vehicles are still running today as long as they’ve been looked after. The first sign of leaf spring problems is when your vehicle sags or leans more to one side than another. A broken leaf spring, meanwhile, might cause a knocking or rattling sound. This often happens when one of the leaves has cracked, fractured or fallen out completely due to heavy use. Worn-out leaf springs might also lead to a reduction in ride height, as the spring packs become flatter.
To check for leaf spring issues, first, check whether the vehicle is sitting level. Flattened leaf springs will be more prone to ‘bottoming out’ over bumps and may not perform correctly under normal driving conditions. When leaf springs become worn, visible cracks are possible and corrosion is also common, so this is something to keep an eye out for. Spring bushes can also become brittle and crack or disintegrate and will need to be replaced.
Due to their construction from thinner materials, coil springs are more prone to thinning and breakage than leaf springs. The first sign of a worn-out coil spring is if you find your vehicle can’t carry as heavy a load as it once could without kicking up a fuss.
You’ll also find that you feel the bumps a little more because there’s less resistance and, as with the leaf spring, your ride height will also suffer. You might also notice unusual noise during operation, as well as handling problems, accelerated tyre wear, and even loss of control under heavy acceleration or braking.
Torsion bars twist to absorb the motion when your wheels make contact with a bump or dip so without them, you’d be experiencing a much less pleasant ride. Given their location at the front-to-rear of the vehicle, they can leave themselves open to damage when they make contact with objects in the vehicle’s path. So it’s important to visually inspect them for damage and replace if needed.
As with coil and leaf springs, sagging ride height is the most likely indicator of worn torsion bars. Harsher ride quality is also common, as torsion bars lose their range of torsion and become more brittle. Broken torsion bars tend to cause serious ride issues and accompanying noise.
Height Adjustable Suspension
Some premium 4WD models can be factory-fitted with complex suspension setups like Toyota’s Kinetic Dynamic Suspension System (KDSS) or Air Ride suspension. These systems use compressed air or fluid-filled reservoirs to raise or lower the vehicle, either on-demand or automatically. Unfortunately, once these systems start to age, they can become unreliable and are very costly to fix.
Whilst it is difficult to offer general diagnostic advice given the diverse nature of different manufacturers’ systems, common issues include loss of ride height, leakage, or inoperable height adjustment selection. In some cases, aftermarket solutions are available to replace them with conventional suspension setups that will allow the vehicle to remain serviceable, but once again it will depend on the specific make and model.
Replacing Suspension Components
If your vehicle’s suspension is worn to the point where components have started to fail, you should consider the condition of the remaining springs, shocks or torsion bars. Now could be a good time to invest in a quality integrated replacement suspension system. This could add years to the lifespan of your vehicle and, in some cases, could essentially bring it back from the dead. Note, however, that you’ll want to do your research first and ensure you’re getting a replacement system that is compatible with your ride.
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