Replacing Shock Absorbers

While most drivers have heard of a shock absorber. Very few realize what they do and also how important they are for safety. Like all moving parts of a car, a shock absorber can wear out over time. This makes it necessary to replace it.

Knowing when to replace the shock absorber is not always obvious. The lifespan of a shock absorber depends on a large number of variables. Car make / model, the mileage traveled and the type of aggressive road surfaces driven.

Depending on the quality of the shock absorber that is fitted, 4-5 years seem to be approximately the average life of a shock absorber. With this in mind, a typical car could go through 3 or 4 in its lifetime.

Sport or street suspension, is reasonable and worth taking into account to replace them at some point.

First: What is a shock absorber?

In a nutshell, the shock absorber controls unwanted movement of the car body. It does this by controlling the movement of the wheels. Springs absorb bumps and changes in road surfaces. While the shock absorber controls / dampens the movement of the wheels after that. Without them, car wheels would swing uncontrollably every time they hit a bump. This is not only uncomfortable, but also dangerous! These two things combined cause the tires to lose contact with the ground.

A selection of typical designs of front and rear shock absorbers In effect, the job of the shock absorber is to keep the tires in contact with the road.

The way they do this varies from car to car, but in principle it is the same. In sport shock absorber models, the damping is 'firmer', which can be a bit less comfortable. What this means is that body movements are controlled more rigidly.

Most modern cars use telescopic shock absorbers which feature a piston and valve arrangement inside a tube filled with oil, they are hydraulic shock absorbers and as the wheel rises, it shortens the shock. The oil is forced into the shock through small holes in the piston.

This slows down and controls the movement of the wheel as the spring oscillates. Some more sophisticated hydraulics have an additional gas chamber inside this arrangement. This allows greater control and 'smooths' the movement. There are also many different types of adaptive or electronically controlled damping systems. It is possible to alter the firmness of the shock absorber in the movement to suit the road surface or driver preference.

How to tell if hydraulic shock absorbers need to be replaced.

As shock absorbers wear out, they become less effective. For example, damping becomes less and less. As the effectiveness of the hydraulics degrades, it is not always easy for the average driver to notice this. You can inspect them within the wheel arches to detect signs of leakage.

Oil stains are a clear signal, you should replace the shock absorber as soon as possible. Wear like this is also an instant NCT / MOT failure. Not all worn shock absorbers have leaks, so don't rely on that method.

Scalloped dips in the tire are another thing to watch out for on the tire edges. The technical name for this cupping and although other worn suspension parts can cause damage or wear, it is more common in shock absorber wear.