Types of shock absorbers and when to replace them

Types of shock absorbers and when to replace them

What are shock absorbers?

In an ideal world, all road surfaces would be even and smooth, allowing you to drive freely without worrying about your tyres or suspension system. Unfortunately, bumps, potholes, and rough roads are an everyday reality for drivers. Thankfully, modern vehicles have efficient damping systems which reduce the vibrations and unwanted movements caused by driving on uneven surfaces. The shock absorbers play a key role in this.

Hydraulic shock absorber

Shock absorbers, also known as suspension dampers or “shocks”, are devices that balance the compression and rebound movements of the suspension springs. They also cushion the body components from shocks and reduce the intensity of vibrations. They do all this by converting kinetic energy into thermal energy. For example, when a car goes over a bump, the springs react and absorb the kinetic energy. To stabilise the movement of the car, this energy must then be dissipated. A piston is actuated in the shock absorber cylinder, pushing out the oil inside. This oil has to be forced through small openings or absorber valves, creating resistance. In turn, the resistance slows down the piston and suspension movement while generating heat.

What are shock absorbers

These components are essential for maintaining road contact, vehicle stability, and control. If your shock absorbers aren’t working properly, you may notice that the vehicle bounces uncontrollably and swerves when turning. It will also negatively affect the vehicle’s braking efficiency.

Types of shock absorbers

Nowadays, the most common suspension dampers are hydraulic, however, there are many different kinds of hydraulic devices with varying designs and components. Here are three popular types of dampers that are used in modern vehicles:

  • Twin-tube shocks
    These have two cylinders. The inner cylinder contains the piston and shaft, and the outer one acts as a fluid reservoir, also containing a low pressure gas for absorbing vibrations. A valve controls the flow of fluid between the cylinders. One of the main advantages is that they are super affordable. However, there is a higher risk of oil foaming when they are subjected to severe driving conditions, which ultimately reduces the effectiveness of the dampers.
  • Monotube shocks
    As the name suggests, these components consist of a single tube which houses the piston, shock absorber fluid, and gas. They have larger pistons and contain more oil than traditional twin-tube shocks, allowing for greater damping precision and improved heat dissipation. Foaming is avoided as the oil and gas remain completely separate at all times, thanks to the free-floating piston that divides them. On the other hand, you may notice that the ride is stiffer as a result of the high pressure gas. The components are also much more expensive to produce and more vulnerable to external damage.
    Types of shock absorbers: monotube shocks
  • Remote reservoir shocks
    These are advanced products designed with an external reservoir and external hose which connects the main cylinder to the oil tank. Its design increases the oil capacity of the absorber and therefore dissipates heat more effectively. There is also less pressure buildup, making the components more durable. They are ideal for off-road and high-performance vehicles. The downside is that, due to these characteristics, they are very expensive and not recommended for standard vehicles.

How long should they last?

As a general rule, you can expect your shock absorbers to last for at least 4 to 5 years unless they are subjected to extreme driving conditions. The replacement interval will largely depend on the driver’s habits, type of vehicle (e.g. light or heavy-duty), condition of the roads and vehicle’s mileage. Off-roading, carrying heavy loads or frequently driving over potholes and rough surfaces will cause the components to wear out faster. It is advisable to inspect them annually or at least once every 50,000 miles.

It is important to replace them when they are faulty for your own safety and the safety of the passengers. If you don’t you could lose control of your vehicle the next time you encounter a bump in the road or pothole.

Signs that the shock absorbers need to be replaced

  • ! A rough or bumpy ride. If the vehicle bounces more and you feel like you are going to lose control of it when driving on uneven surfaces, there is a strong possibility that the shock absorbers are faulty.
  • ! The vehicle nose dives when braking. This can occur if the shocks or struts are worn or damaged.
  • ! Fluid leaks. If you notice that the hydraulic fluid is leaking out, this is a clear sign of damage. The loss of fluid will reduce the pressure, causing the components to become ineffective.
  • ! Uneven tyre wear. A faulty suspension system will directly impact the wheels.
    Symptoms of wheel alignment problems: uneven or abnormal tyre wear
  • ! Steering difficulties. If the steering wheel is abnormally stiff or the vehicle sways or leans to one side when turning, this could be an indicator that it’s time for a replacement.


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