Shock absorbers for trailers and semi-trailers: function, wear and maintenance

The shock absorbers for trailers and semi-trailers they play a fundamental role in the behavior of the vehicle on the road. Although attention is often focused on the tractor, the trailer suspension system is also continuously subjected to loads, vibrations and stresses.

Efficient shock absorbers help control suspension movements, improving vehicle stability and correct contact of the tires with the road. Because of this wear and maintenance of semi-trailer shock absorbers they should not be underestimated.

What are trailer and semi-trailer shock absorbers used for?

The main function of the shock absorber is to control the oscillations generated by the suspension when the vehicle encounters irregularities, variations in the road surface, braking or other load transfers.

Without adequate damping, the suspension would continue to oscillate after every load.

In the shock absorbers for trailers and semi-trailers, this check becomes particularly important considering the different conditions in which the vehicle can travel: fully loaded, partially loaded or unloaded.

The shock absorber then works together with the other suspension components to help:

• control the oscillations of the axes;
• maintain smoother contact between tires and road;
• improve trailer stability;
• limit excessive movements and vibrations;
• reduce stress on other suspension components.

Shock absorbers and pneumatic suspensions for semi-trailers

Many trailers and semi-trailers use pneumatic suspension equipped with air springs.

However, air spring and shock absorber perform different functions.

The air spring supports the load and allows the suspension to adapt to operating conditions, while the shock absorber controls the speed and amplitude of the oscillations.

For this reason, during maintenance of semi-trailer suspensions, it is important to evaluate the system as a whole rather than focusing solely on a single component.

How to recognize a worn shock absorber?

Shock absorbers are subject to progressive deterioration due to mileage, road conditions, loads and methods of use of the vehicle.

Among the possible signs of worn shock absorbers on the semi-trailer can include:

• anomalous oscillations after road irregularities;
• less stable behavior of the trailer;
• uneven tire wear;
• obvious fluid leaks from the shock absorber;
• damage to bushings or attachments;
• excessive movements of the axes.

Not all of these phenomena necessarily indicate a faulty shock absorber. A professional check of the entire suspension is therefore necessary to correctly identify the source of the problem.

Maintenance of shock absorbers on trailers and semi-trailers

There is no replacement interval valid for every application. A semi-trailer used mainly on the motorway can be subjected to very different conditions compared to a vehicle used on uneven surfaces or with frequent load changes.

The maintenance of trailer shock absorbers should therefore include periodic checks of the condition of the component, connections, bushings and surrounding elements.

It is also important to check the condition of the tires and air springs, when present, because a fault in one part of the suspension can influence the behavior of the other components.

How to choose shock absorbers for semi-trailers

When the time comes for replacement, identify the correct replacement for the semi-trailer it is essential.

Dimensions, stroke, type of attachments, axle, application and technical specifications must be compatible with the vehicle. The OE code can represent an important reference for identifying the correct aftermarket correspondence.

The choice should therefore not be based solely on price, but consider compatibility, construction quality and application characteristics.

Way Assauto: shock absorbers for trucks, buses and trailers

With over a century of experience in the industry, Way Assauto develops and produces shock absorbers for industrial vehicles, with solutions dedicated to trucks, buses and trailers for the OE and aftermarket markets.

Production experience, knowledge of the different applications and attention to technical characteristics allow us to respond to the needs of a sector in which reliability and correct identification of spare parts represent fundamental elements.

Because even behind the stability of a semi-trailer there is a component called upon to work continuously: the shock absorber.