Ensure Safe Braking with Properly Adjusted Automatic Slack Adjusters
Table of Contents
- Introduction
- Importance of Proper Brake Adjustment
- Checking the Geometry between Air Chamber, Push Rod, and Camshaft
- Measuring Free Stroke
- Measuring Applied Push Rod Stroke
- Checking the Movement of the Adjusting Mechanism
- The Six-Pack Method for Adjusting Slack Adjusters
- Common Causes of Slack Adjuster Problems
- Importance of Greasing and Using the Right Grease
- Other Components to Check for Proper Adjustment
- Conclusion
1. Introduction 👋
In the fast-paced trucking industry, ensuring that your brakes provide safe, effective, and efficient braking is of utmost importance. One key component of the braking system is the automatic slack adjuster. This article will guide you through the process of checking and adjusting automatic slack adjusters to ensure they are working properly. By following these steps, you can maintain the proper adjustment of your brakes and promote overall safety on the road.
2. Importance of Proper Brake Adjustment
Proper brake adjustment is crucial for the safe operation of commercial vehicles. When brakes are incorrectly adjusted, it can lead to uneven braking, reduced stopping power, and increased wear on brake components. This can compromise the overall safety and efficiency of the braking system. Regularly checking and adjusting automatic slack adjusters is essential to maintain optimal brake performance.
3. Checking the Geometry between Air Chamber, Push Rod, and Camshaft
To ensure that your automatic slack adjusters are functioning properly, it is important to check the geometry between the air chamber, push rod, and camshaft. This check helps identify any potential mounting or positioning issues that may affect the adjustment of the brakes.
Using a small square, measure the angle between the center of the air chamber push rod and the center of the camshaft. The ideal angle should be 90 degrees. If the angle deviates from 90 degrees, it indicates a problem with the mounting or positioning of the components. Ensure that the air chamber is correctly mounted on the bracket and that the yoke is properly positioned on the push rod.
4. Measuring Free Stroke
Measuring the free stroke of the air chamber push rod is an important step in checking the adjustment of automatic slack adjusters. The free stroke is the movement between the brake shoe friction and the brake drum.
To measure the free stroke, chock the wheels and release the brakes. Use a pry bar to pull the push rod away from the air chamber. The movement should be between one half and 5/8 of an inch, which is approximately the width of your thumb. If the free stroke measurement falls outside this range, it indicates an issue with the adjustment of the automatic slack adjusters.
5. Measuring Applied Push Rod Stroke
The applied push rod stroke is another critical measurement used by the Department of Transportation (DOT) during brake checks. This measurement determines the distance the push rod travels when the brakes are applied.
With the brakes still released, measure the push rod travel distance from the back of the air chamber. You can use a stroke indicator, a zip tie, or a soapstone to mark the position on the push rod where it enters the air chamber. Compare the measurement to the maximum allowable stroke for your air chamber size. For a type 30 chamber, the maximum allowable stroke is two inches, while a type 30 long stroke chamber allows for a maximum stroke of two and a half inches.
6. Checking the Movement of the Adjusting Mechanism
The movement of the adjusting mechanism inside the slack adjusters plays a vital role in maintaining proper adjustment. If the internal adjusters are not working correctly, the automatic slack adjusters will not maintain the desired adjustment.
The "Six-Pack" method is an effective way to check the functionality of the internal adjusters. This method can also be used to adjust slack adjusters that are slightly out of adjustment. To perform this check, you will need an assistant.
Start by backing off the slack adjuster by half a turn. Then, allow the air system to build full system air pressure. Place a wrench on the adjuster nut and have your assistant apply the foot brake. Observe the movement of the wrench as the push rod and slack adjusters adjust the brakes.
The "Six-Pack" consists of making three full brake applications after achieving full system air pressure. Each time the foot brake is applied, check the movement of the wrench. This method helps determine if the internal adjusters are working properly. If the adjusters are functioning as expected, there should be a noticeable adjustment after the "Six-Pack" procedure.
Remember to bring the slack adjuster back into proper adjustment before moving on.
7. Common Causes of Slack Adjuster Problems
Several factors can contribute to slack adjuster issues. One common cause is insufficient or improper greasing. Greasing the slack adjuster with the appropriate grease not only helps to maintain proper adjustment but also ensures smooth operation.
Worn or corroded components can also affect the performance of slack adjusters. Camshafts, camshaft bushings, clevis pins, and brake attaching hardware should be regularly inspected for signs of wear or corrosion. Any worn or corroded components should be replaced promptly to avoid further complications.
8. Importance of Greasing and Using the Right Grease
Proper greasing is essential for the smooth operation and longevity of automatic slack adjusters. The right grease for slack adjusters is typically a high-quality, lithium-based, NLGI grade 2 grease. Using the correct grease helps reduce friction and wear, keeping the adjusters in optimal condition.
Ensure that the slack adjusters are adequately greased during routine maintenance. Follow the manufacturer's recommendations regarding the type and frequency of greasing to obtain the best results.
9. Other Components to Check for Proper Adjustment
While automatic slack adjusters play a significant role in maintaining brake adjustment, other components should also be inspected for proper adjustment at regular intervals. These include the camshafts, camshaft bushings, clevis pins, and brake attaching hardware.
Worn or damaged components can lead to improper brake adjustment, compromising the performance and safety of the braking system. By regularly checking and replacing these components as needed, you can ensure that the automatic slack adjusters work in conjunction with other brake components for optimal adjustment.
10. Conclusion
Proper adjustment of automatic slack adjusters is crucial for maintaining the safety and effectiveness of your braking system. By regularly performing checks and adjustments, you can ensure that your brakes provide reliable and efficient stopping power when needed. Take the time to inspect the geometry, measure the free and applied strokes, and check the movement of the adjusting mechanism. Additionally, prioritize greasing and replace any worn or damaged components. Remember, well-adjusted brakes contribute to safer roads and smoother journeys.
Highlights
- Maintain proper brake adjustment for safe operation
- Check geometry between air chamber, push rod, and camshaft
- Measure free stroke and applied push rod stroke
- Verify movement of the adjusting mechanism
- Use the "Six-Pack" method to test internal adjusters
- Grease and use the correct grease for slack adjusters
- Inspect camshafts, camshaft bushings, clevis pins, and brake attaching hardware
- Regularly replace worn or corroded components for optimal adjustment
FAQ
Q: How often should I check and adjust my automatic slack adjusters?
A: It is recommended to check the adjustment of your slack adjusters during routine maintenance, which is typically performed every three to six months. However, it is best to consult the manufacturer's guidelines for your specific vehicle and application.
Q: What is the significance of the 90-degree angle between the air chamber push rod and the camshaft?
A: The 90-degree angle between the air chamber push rod and the camshaft ensures the proper alignment and movement of the braking components. Any deviation from this angle indicates a potential mounting or positioning issue that needs to be addressed.
Q: Can I use a different grade of grease for my slack adjusters?
A: It is crucial to use the appropriate grease recommended by the manufacturer for your slack adjusters. Using the wrong grade of grease can lead to poor lubrication, increased friction, and premature wear.
Q: Why is it important to check components other than the slack adjusters for proper adjustment?
A: While slack adjusters play a significant role in brake adjustment, other components such as camshafts, camshaft bushings, clevis pins, and brake attaching hardware can also affect the overall adjustment. Checking and replacing these components as needed ensures the proper functioning of the entire braking system.
