If you’ve ever driven too quickly over a speed hump or have gone over a pothole, you’ll no doubt know the value of your car’s shock absorbers. But what exactly are they, what are the different types, and why is it important to keep them in good shape? Here we’ll answer all these questions and more about shock absorbers.
Shock absorbers are one of the most important parts of a car’s suspension system, which also consists of the tyres, springs, joints, bushes and other components. The earliest versions of shock absorbers were very rudimentary and were first used on horse-drawn carriages and trains. They generally consisted of pieces of metal of varying lengths layered on top of each other and attached to the axle, allowing movement of the wheel up and down in order to dampen the force of bumps on the road. However, due to their stiffness, they were not very good at giving occupants a much smoother ride.
Later versions utilised hydraulic dampers which included a piston attached to a pressurised housing containing fluid (usually oil) or gas, which converted the kinetic energy produced by hitting a bump into thermal energy (heat). As the fluid needs to flow through small holes, this creates resistance and allows the shocks to absorb the force of the bump and dissipate it.
If your shock absorbers are too stiff, you will notice this whenever you hit a bump as the kinetic energy will not be absorbed fully by the shock absorbers but will travel into the rest of the vehicle. If the shock absorbers are too soft, the car can bounce around too much even when hitting small bumps or even when travelling on flat ground without any bumps or when stopping.
In addition to absorbing the force of hitting bumps and holes on the road, shock absorbers perform a very important role in helping to keep the tyres in constant contact with the road. When the car isn’t moving or is travelling over a smooth road, the piston sits midway in the pressurised housing, pushing down and helping the tyre to connect with the road.
Depending on the kind of vehicle you drive, there are three main types of shock absorber units available.
Conventional telescopic shock absorbers are the cheapest and simplest type of shocks, which are generally filled with air and do not provide the smoothest ride. You’ll often find them on cheaper vehicles and due to their low-cost construction, they will always be replaced instead of repaired.
Strut-type shock absorbers are built to withstand higher loads and can adapt to different road conditions. They can be found on small, medium and large vehicles and can last for tens of thousands of kilometres. Strut-type shock absorbers come in two types: sealed, which are completely replaced when necessary; and repairable, which, as their name suggests (they’re also called McPherson struts), can be repaired rather than replaced.
Spring-seat shock absorbers are basically a combination of the above two types of shock absorbers, however they are not designed for heavy loads.
In addition to the above, shock absorbers themselves can also come as twin-tube or mono-tube units, with differences in how damping forces operate. With twin tubes, the piston valve dampens the force when the piston rod extends, while the base valve helps to dampen the force when the rod contracts. Mono tubes work differently in that the piston valve is able to dampen the force when the piston rod expands or contracts. Twin tubes are usually found on most types of vehicles, whereas mono tubes are generally used for sport suspension, as well as being great at dissipating heat and being able to be tuned easily.
When should you replace your shock absorbers? Depending on the kind of driving conditions you usually encounter, such as city and highway driving or lots of extreme off-road driving, most good-quality shock absorbers should last for five years as a minimum, or even up to ten years. The more the shock absorbers have to work, the more quickly they will start to fail, so slowing down to go over speed bumps and trying to avoid potholes or other road hazards will help to extend their lives.
Whether you have a small hatchback, a mid-size sedan or wagon, an SUV, a 4×4 or a sports/performance vehicle, Pedders has a wide range of replacement shock absorbers to match your vehicle.