When to replace the car shocks and struts?

The car’s shocks and struts, along with the springs, are important parts of the car’s suspension and, after a certain mileage and road conditions, they should be checked and, if worn, replaced.

The car’s suspension has the role to absorb the bumps caused by the unevenness of the road. Good shock and struts keep the wheels in constant contact with the tread surface regardless of its condition, thus ensuring good grip and efficient braking. As a result, these parts are essential for traffic safety.

The struts or shocks control the size of the suspension’s oscillations by compensating for the excess energy transmitted from the springs or wheels by absorbing the shocks caused by road bumps and stabilizing each wheel on the tread surface. These suspension parts absorb the vibrations generated by the condition of the road and do not allow them to reach the body thus improving the comfort in the car’s cabin.

In contrast, worn shocks and struts result in poor steering wheel grip, loss of steering ability, and, consequently, greater braking distances. When the shocks are worn, they also cause premature wear of tires and other parts, causing the vehicle to tilt sharply forward during braking, or backward when accelerating. Their wear also generates an increased balance in turns.

Symptoms of bad or worn shocks and struts

Shocks and struts are permanently required while the vehicle is running and are worn out.

Their degree of wear depends on the number of miles traveled, the profile of the road traveled, the state of loading the car, the tire pressure and their degree of wear, but also on the driving style practiced.

Shocks and struts faults can lead to vehicle’s instability when driving, especially in turns.

The first signs of worn shocks and struts can be detected relatively easily: some mechanical noises appear in their area with problems. In turn, the car tends to move laterally or gives the feeling that it floats, there are losses of grip for the wheels when accelerating.

At the same time, abnormal tire wear and even oil leakage occur on the body of a shock or strut.

We can also mention an increased tendency to aquaplaning on a wet road, increased braking distance, and, by increasing the wear of the tires, their service life decreases proportionally.

When driving with damaged or worn shocks and struts you may experience the following symptoms:

1. Low comfort

The shocks and struts, together with the helical springs, have the role of reducing the shocks or bumps caused by a bad road while keeping the wheels “glued” to the asphalt. Worn shocks, however, will leave, in the first phase, the wheel to “jump” after the impact with a road leveling, allowing then the whole body to swing uncontrolled on the springs. This results in an uncomfortable ride, noise and increased wear of the suspension components.

2. Maneuverability and low stability when avoiding obstacles

Below we can see, in a comparative test, how two identical cars behave in the milestone test, one being equipped with new shocks and struts and the other with the same parts but 50% wear.

The car with new shocks or struts manages to keep the trajectory dictated by the driver, while the other one becomes unstable, tends to subvert and the rear axle loses grip and slips, causing the car to have a “boat behavior”.

3. Increased braking distance

Although it seems unbelievable, yes, the worn shocks or struts increase the braking distance of the car by up to 5 meters. The proof is in the video below.

Explication? Worn shocks and struts “break the grip” on sudden braking (allowing the wheel to lift millimeters from the ground repeatedly) and thus the braking force is not fully transmitted to the road.

4. Low stability in tight corners

Exits from the freeway or tight curves: each one of them can endanger us if we drive with the used shocks. As you can see in the video below, the worn struts or shocks are not able to keep the wheel from the outside of the turn permanently on the asphalt, which leads to instability, the wheels begin to pull the wheel and there is a risk of skidding.

5. Low stability in windy conditions

In strong wind or when we pass a truck or other high-speed vehicle, the air pressure created by it can deflect the car or even get it off the road if the shocks do not work to their full potential. This is because the worn struts allow the car to tilt sideways much more than it should, which makes it easy for the car to steer in the opposite direction.

6. A bad lighting of the road at night

The balance of the suspension created by the weak shocks can pose problems at night for both the driver in question and other traffic participants, because the direction of the headlights light varies constantly up and down, even in the case of minor differences in the road.

How to check the shocks and struts

To evaluate the operating status of the suspension system alone, it is recommended that the car body be pressed periodically in the area of ​​the shocks. If following this procedure it is found that the car inclines too much and too fast on one side or another, which means that the shocks or the spring have been weakened.

Pay attention to the noises the car makes while driving. Other indications may be loud noises when driving or shocks when running on uneven surfaces. If you see a difference in the vehicle’s height (inclination) when comparing the wheel suspension on the same axle, the conclusion is obvious: you have to change the shocks or struts.

There is a method of verifying the condition of the shocks using an adhesion test on the stand. This test consists of measuring the weight borne by each wheel on the two axles during the swing of the platforms on which the wheels are arranged.

The oscillation frequency of the stand platforms at which the adhesion is determined is between 12-18 Hz. This method of testing the shocks is also used in the technical inspection carried out on cars.

The test takes a maximum of 5 minutes and determines their exact condition. The test result on each wheel and each deck, displayed on a screen, indicates the minimum weight determined during the oscillations relative to the static weight on the wheel.

The higher the measured value of grip on the stand, the better and better the car is for the road. The measured values ​​can be appreciated as follows:

– Good adhesion – values ​​over 60%,

– Acceptable adhesion – values ​​between 20 and 60%.

– Weak adhesion – values ​​below 20%.

A difference between the grips of the two wheels on the same axle less than 15% is considered acceptable, and a difference value over 15% is considered unacceptable, exaggerated, and indicates the wear of the shocks and struts on one of the wheels.

In the case of adhesion with the measured value below 20% (weak) or a difference between the two wheels on the same axle greater than 15%, it is necessary to replace the shocks considered worn.

It is good to replace both shocks on the same deck because when a failure occurs as a result of wear, the other pair usually registers over 50% wear as well.

In case of replacement of a single shock, the new one will take over the road shocks more correctly and there will be an imbalance between the two, an imbalance that ultimately leads to accelerated wear of the new one. Let’s not forget that by using damaged shocks, the springs also wear losing much of their original elastic properties.

How many miles do shocks and struts last?

The suspensions usually change to a certain number of kilometers indicated in the car’s book, usually around 60,000 kilometers (37300 miles), or every 5-6 years, and then every 20,000 km (12400 miles) again – because worn or defective shocks increase the risk accidents, but the replacement must be done much faster if the roads on which the car was operated have many bumps and potholes.

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