Shock absorbers and struts are parts of the suspension. They absorb shocks from speed bumps and potholes and keep your car running smoothly and stable. They also absorb the energy of the springs and prevent the vehicle from bouncing excessively, thus keeping good contact with the road. 

The difference between a shock absorber and a strut

What is the difference between a shock absorber and a strut? A strut is a shock absorber that consists of one unit. It is built in with a coil spring and a strut mount. 

A typical strut consists of a coil spring to support the weight of the vehicle, a housing to make the strut strong and a damper inside the housing to control the movement of the suspension. The bottom of the strut housing is connected to the steering mechanism.

Shock absorbers are actually oil pumps. At the end of a piston rod is a piston that works against the hydraulic fluid in a tube.

How do McPherson struts work? 

A McPherson strut is a type of suspension in which the strut also functions as a support arm and in the case of the front wheels as a pivot. Due to its efficient design, the system is frequently used. Especially small cars benefit from it because there is often little space for a larger construction. McPherson struts work independently of each other and are found in almost all contemporary cars. 

Replacing shock absorbers

Struts and shock absorbers require no maintenance. Does this mean they never need to be replaced? No, struts and shock absorbers wear out, especially when the roads are bad. This is not often the case in the Netherlands, but if a car has driven many kilometres, there comes a time when the shock absorbers have to be replaced. Sometimes, shock absorbers start to leak and become too soft. 

Characteristics and symptoms replaced Shock absorber

  • There is leakage, the oil leaks out of the shock absorber and reduces its effectiveness. 
  • A knocking / ticking sound can be heard on uneven surfaces. 
  • The car continues to sway for a long time after passing a speed bump, for example.
  • The car tilts a lot in bends. Of course, this also depends on the character of the car. American cars are simply less rigidly sprung than cars of German manufacture. 
  • The car becomes more sensitive to crosswinds. You can feel this in the steering wheel when there is a crosswind and you have to hold the steering wheel more firmly than usual. 
  • During (hard) braking, the nose of the car dips. 

Causes of less effective shock absorbers

As mentioned earlier, wear may occur. In the Netherlands, this wear is limited due to the good roads, but if a car has a high mileage, they may be worn out. Besides this regular wear and tear, there are a number of other causes that make it necessary to replace shock absorbers: 

  • Driving too fast over speed bumps
  • Driving through a deep pothole 
  • Hitting or driving into a curb 

In the above cases, it is possible that one shock absorber is damaged, for example at the right front. In this case, it is wise to replace the left shock absorber as well. This limits the chance of deviating driving behaviour. 

Do you have to replace all four shock absorbers when one is worn out? 

Should I replace all four struts/shock absorbers at the same time? This is not necessary unless they are all bad. For example, if your car has four old shock absorbers that are not very expensive to replace and you want a car that runs like new again, you could replace all four. So it is not always necessary to replace all four at once. On the other hand, if the front or rear is bad, it is wise to replace two. So replace the front two or rear two at the same time. 

Do the coil springs also need to be replaced? 

Do coil springs or spring struts have to be replaced when replacing shock absorbers? The answer is no: if the springs or spring supports are in good condition, they can be reused with new struts/shock absorbers. However, if a vehicle is old and it is known that spring gate mountings in this vehicle are failing, it makes sense to replace the strut mountings as well.

Stabiliser rods also replaced?  

Do the struts have to be replaced by stabiliser rods? No, but in some cars swaybar links are connected to the struts, see the picture above. A stabiliser bar has to be removed to replace the strut. Often the nut that holds the link grips, making it difficult to remove without damaging the link. 

In this case, a stabiliser bar must also be replaced. Sway bar links are not very expensive. 

Cost of replacing shock absorbers

The cost of replacing shock absorbers varies greatly depending on the brand and the hourly rate of a garage. Nowadays, aftermarket parts, including shock absorbers, are cheap. They are available from as little as €50 each on various car parts websites. An experienced mechanic should be able to replace shock absorbers in no more than 3 to 4 hours. The total price will then depend on the hourly rate. Normally, you would have to pay 300 to 400 euros for a front or rear shock absorber.