8 Brake Maintenance Tips for Semi-Trailers


Semi-trailers traveling 65 MPH can take up to two football fields to come to a complete stop, and that is with fully functioning semi-trailer brakes. If any component of the semi-trailer air brake system is faulty, it could extend the distance needed to stop or inhibit stopping altogether.

Unfortunately, brake problems account for 29% of all large truck crashes making the consequences of inadequate brake performance potentially catastrophic. Additionally, semi-trailer brakes are one of the main reason semi-trucks receive out-of-service violations.

One of the most important responsibilities semi-trailer owners and operators have is to maintain semi-trailer brakes that work effectively. Here we’ll share 8 brake maintenance tips to keep you and your semi-trailer safe and on the road.

1. Keep an Eye on Air Pressure Levels

Semi-trailer brakes rely on adequate air pressure levels to function properly. Be sure to take a look at your air pressure gauge before heading out on the road so you know everything is in good working condition. Semi-trailer air pressure readings should be between 100 psi and 125 psi. A pressure gauge showing 60 psi before driving indicates semi brakes that need service.

2. Check Semi-Trailer Brake Linings and Hoses

Brake linings are an integral part of semi-trailer brakes and because of their frequent use, it’s imperative that they be checked regularly. When you check brake linings, check that they aren’t loose or soaked with lubricant. Linings should be dry, not damp with oil or grease. As linings wear down, check that they are at least ¼ of an inch thick.

Hoses are another key component in the semi-trailer air brake system to monitor. Take a look at where the semi-trailer air line connections occur in the brake area to avoid any detached hoses. Air hoses also need to be evaluated for cracks or wear. Any hoses that show signs of damage should be replaced.

3. Apply Grease to Slack Adjusters

To keep your brake system running smoothly, apply grease to your slack adjusters. Slack adjusters come into play every time your semi air brakes are used, and they help maintain correct alignment.

Whether your semi-truck has manual or automatic slack adjusters, it’s important to remember to keep both lubricated for an effective semi-trailer air brake system. Sometimes automatic slack adjusters get neglected because they don’t require as much manual adjusting, but it’s still important to keep them greased. Applying grease to your slack adjusters will help you avoid brake failures.

4. Inspect and Grease S Cams

S cams perform the important job of pushing the brake shoe into the brake drum. This action is what helps your semi-trailer brake so it’s imperative that the motion occur freely and without impediment. Proper lubrication will not only ensure semi-trailer brakes don’t seize, but it will also support the lifespan of your S cams. Make it a point to inspect the S cams between shoe changes and add more lubricant if necessary.

5. Perform Visual Inspection of Wheel and Brake Chambers

Safe semi brakes also depend on well-maintained semi-trailer wheels. Performing regular wheel inspections will help prevent problems from arising. Clean wheels and examine exposed areas for damage such as:

  • Cracks
  • Wear
  • Corrosion

Take time to do a visual check on the inner dual wheel while the outer wheel is removed. Be especially careful to check areas where common cracks are found, such as between bolt holes.

It is also important to visually inspect semi-trailer brake chambers for noticeable problems. Look for damage to the chamber or bent pushrods. Loose or missing parts such as clamp bands, caging bolts, or dust plugs can allow contaminants like water or dirt to enter the chamber and result in erosion on the power spring.

When replacing chambers, stick with ones that match what you are replacing. In the short-term, a chamber with a different pushrod length than the OEM specification may not cause problems, but in the long-term, it can cause brake issues.

6. Regularly Replace Brake Shoes and Other Parts

Over time, semi-trailer brake shoes wear down and need to be replaced. Many brake shoes have built-in wear indicators that make it clear when new brake shoes are needed. It is recommended that you replace all interrelated brake parts at the same time. This means when you replace brake shoes you should also look to replace:

  • Brake drums
  • Springs
  • Bushings
  • Pins

Brake drums can wear and crack from heat, so regular replacement is of utmost importance. Schedule regular semi-trailer repair and maintenance to keep your semi-trailer brakes operational. 

7. Check Anti-Lock Braking System

A semi-trailer’s anti-lock braking system (ABS) is an electronic safety system that prevents wheels from locking up and ensures wheels stay in touch with the ground when brakes are applied. While your anti-lock braking system may not require frequent maintenance, it is a good idea to check it at least once a year during your annual safety inspection. To ensure your semi-trailer brakes perform at their best, never ignore ABS warning codes. These notifications serve to alert drivers that there may be a braking system issue that needs attention.

Some common triggers that set off the ABS are:

  • Wheel speed sensor wire is broken
  • A wheel bearing has gone bad
  • A tone ring is dirty
  • Battery voltage is low
  • The ABS module itself is malfunctioning

8. Evaluate Air Dryers Monthly

Air dryers provide the semi-trailer air brake system with air that is free of liquid, solid, and aerosol contaminants. Removing water and oil before they reach the air brake system is vital to its operation. Conduct monthly evaluations of your air dryer by checking for moisture in the air brake system. If you do find moisture present, it may be time to replace the air dryer cartridge.  

Visit Hale Trailer for All Your Maintenance Needs

Hale Trailer Brake & Wheel Inc. is your one-stop-shop for all things semi-trailer. Whether you need parts or repair services or are looking for semi-trailers for sale or semi-trailers for rent, we have what you need!

Our knowledgeable team is eager to answer any questions you may have, and with an unmatched selection of inventory, you are sure to find what you’re looking for. View our locations to find which of our 12 shops is most convenient for you or give us a call at 800-232-6535 today!

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