Semi-Trailer Brakes Maintenance Tips

Semi-trailers have a larger mass and greater inertia, requiring longer braking distances than other vehicles. However, if any component of the braking system of a semi-trailer malfunction, it can further extend the braking distance and increase the risk of accidents.

It is the responsibility of every driver to ensure that the semi-trailer’s braking system is functioning effectively. Here, we will share seven brake maintenance tips and how to adjust the brakes of a semi-trailer.

Semi-Trailer Brakes

Semi-Trailer brakes maintenance

Air Pressure Level

The braking system of a semi-trailer requires sufficient air pressure to function properly. Before hitting the road, check your air pressure gauge to ensure that the reading is between 100 psi and 125 psi. This will put the trailer in good working order. If the pressure gauge shows 60 psi, then the braking system of the semi-trailer needs to be repaired.

Brake Pads and Hoses

Brake pads are an essential part of the braking system of a semi-trailer and should be checked regularly since they are frequently used. When checking the brake pads, make sure that the pins are not loose and that they have not been soaked in lubricant. Normally, the pads should be dry and should not be wet with oil or grease. If there is any wear and tear on the pads, make sure that their thickness is at least 1/4 inch.

Hoses are another important component that should be inspected regularly. Check the airlines of the semi-trailer to see if they are loose or have any cracks or wear. Any hoses that show signs of damage should be replaced.

Slack Adjusters

To ensure that the braking system operates smoothly, lubricating grease should be applied to the slack adjusters. The function of the slack adjusters is to help maintain alignment.

Automatic slack adjusters can be easily overlooked in this regard since they do not require as much manual adjustment. However, maintaining lubrication is still important.

Slack Adjusters


S-cams are responsible for the crucial task of pushing the brake shoes into the brake drums. This is the primary action of breaking a semi-trailer, and it should be performed without any hindrance. Proper lubrication can ensure this.

Wheels and Brake Chambers

When checking the wheels, it is important to inspect for damage in exposed areas, such as cracks, wear, corrosion, etc. Pay special attention to the area between the bolt holes, as this is where cracks are most likely to occur.

In addition to inspecting the wheels, it is also necessary to visually inspect the brake chambers for any obvious issues. Look for damage to the chamber or bent pushrods.

Loose or missing components such as clamps, cage bolts, or dust plugs can allow water or dirt contaminants to enter the chamber and cause erosion to the power spring.

Brake Shoes and Other Parts

Brake shoes on a semi-trailer can wear out over time and may need to be replaced. Many brake shoes have built-in wear indicators that will signal when it’s time for new brake shoes. When replacing them, it’s best to replace all related brake components, including brake drums, springs, linings, and pins.

Anti-lock Braking System (ABS)

It is an electronic safety system that prevents wheel lock-up, ensuring that the wheels maintain contact with the ground during braking. It’s best to check the ABS at least once a year during the annual safety inspection. When an ABS warning code appears, it should not be ignored.

Common triggers for ABS issues include

  • Broken wheel speed sensor wires
  • Damaged wheel bearings
  • Dirty tone rings
  • Low battery voltage

How to adjust semi-trailer brakes

1. Find a Safe Location

Before starting the adjustment process, find a flat and level area where you can safely park the trailer. Make sure the trailer is on a firm surface and chock the wheels to prevent any movement.

2. Identify the Brake System

There are two types of brake systems commonly used on semi-trailers: drum brakes and disc brakes. Drum brakes are the most common and require manual adjustment.

3. Locate the Brake Adjuster

On each wheel, you will find a brake adjuster that can be used to adjust the brakes. The adjuster can be accessed through a small slot in the brake drum.

4. Adjust the Brakes

Use a brake adjustment tool to turn the adjuster. Turn the adjuster clockwise to tighten the brakes and counterclockwise to loosen them. The goal is to adjust the brakes so that they have a slight drag when the wheel is turned.

5. Test the Brakes

After making adjustments, test the brakes by applying them while driving at a low speed. Listen for any unusual noises and make sure the brakes engage smoothly.

6. Repeat for all Wheels

Repeat the process for all wheels on the trailer to ensure the brakes are evenly adjusted.

Maintaining the brakes on a semi-trailer is an essential part of keeping it roadworthy and ensuring safe driving. Regular brake maintenance, including adjusting the brakes, can prevent accidents, save lives, and reduce repair costs. By following the steps outlined in this article, you can keep your semi-trailer brakes in good working condition and enjoy safe driving on the road.

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top
Open chat
Need help?
Scan the code
Welcome to Three Horses Trailer
May I know which trailers you are interested in?