Mastering Brake Maintenance: Adjusting Automatic Slack Adjusters
Table of Contents
- Introduction
- Why Brake Maintenance is Important
- Checking the Geometry of Automatic Slack Adjusters
- Measuring Free Stroke
- Measuring Applied Push Rod Stroke
- Checking the Movement of Adjusting Mechanism Inside Slack Adjusters
- Using the Six-Pack Method to Check and Adjust Automatic Slack Adjusters
- Other Possible Causes for Automatic Slack Adjuster Issues
- Benefits of Proper Brake Adjustment
- Conclusion
Introduction
In the fast-paced trucking industry, maintaining a safe and efficient braking system is crucial. Automatic slack adjusters play a vital role in ensuring that brakes are adjusted properly and function effectively. In this article, we will discuss the importance of brake maintenance and provide step-by-step instructions on how to check and adjust automatic slack adjusters.
Why Brake Maintenance is Important
Proper brake maintenance is essential for the safety and efficiency of a truck. Brakes that are not adjusted correctly can lead to excessive wear, reduced stopping power, and even brake failure. Regularly inspecting and maintaining the braking system, including automatic slack adjusters, can prevent costly breakdowns and ensure the safety of the driver and others on the road.
Checking the Geometry of Automatic Slack Adjusters
Before checking the adjustment of automatic slack adjusters, it is crucial to ensure that the geometry between the air chamber, push rod, and camshaft is correct. Using a small square, confirm that there is a 90-degree angle between the center of the air chamber push rod and the center of the camshaft. Any deviation from this angle indicates a potential issue with the mounting or positioning of components.
Measuring Free Stroke
Free stroke refers to the movement between the brake shoe friction and the brake drum. Measuring the free stroke can help determine if there is proper movement and distance. To measure the free stroke, place a pry bar in the push rod yoke and pull away from the air chamber. The movement should be between one-half and 5/8 of an inch, approximately the width of a thumb.
Measuring Applied Push Rod Stroke
The applied push rod stroke is the measurement most commonly used during a brake check. With the brakes released, measure the push rod travel distance from the back of the air chamber. Utilize a stroke indicator or mark the position on the push rod where it enters the air chamber. The maximum allowable stroke varies based on the type of air chamber, with a range from two inches for a type 30 chamber to two and a half inches for a long stroke chamber.
Checking the Movement of Adjusting Mechanism Inside Slack Adjusters
To ensure that the internal adjusters of automatic slack adjusters are functioning properly, a method known as the "six-pack" can be utilized. This method also helps in adjusting slack adjusters. With the wheels chocked and brakes released, back off the slack adjuster by half a turn. Once the air system has built full pressure, apply the foot brake three times while observing the movement of the wrench on the adjuster nut. This process should result in approximately a quarter turn of adjustment.
Using the Six-Pack Method to Check and Adjust Automatic Slack Adjusters
The six-pack method involves making three full brake applications to observe the movement of the wrench as the push rod and slack adjusters adjust the brakes. After three applications, allow the air system to build pressure again and apply the foot brake three more times. By the end of this process, the slack adjuster should be properly adjusted if the internal mechanisms are functioning correctly.
Other Possible Causes for Automatic Slack Adjuster Issues
While a lack of adjustment and internal mechanism issues are common causes of automatic slack adjuster problems, other factors can contribute to their malfunction. Inadequate greasing, using the wrong type of grease, and worn or corroded components like camshafts, camshaft bushings, clevis pins, or brake attaching hardware can also affect the performance of automatic slack adjusters.
Benefits of Proper Brake Adjustment
Ensuring that automatic slack adjusters are adjusted correctly provides several benefits. Proper brake adjustment leads to improved stopping power, reduced brake wear, and extended brake life. It also enhances the overall safety of the vehicle and its occupants. By adhering to regular brake maintenance, fleet owners and repair shops can avoid unnecessary expenses and guarantee the most efficient and safe wheels on the road.
Conclusion
Maintaining and adjusting automatic slack adjusters is an essential aspect of brake maintenance in the trucking industry. By following the steps outlined in this article, truck drivers and maintenance personnel can ensure that their braking systems are in proper working condition. Regular checks and adjustments of automatic slack adjusters contribute to safer, more effective, and efficient braking, giving drivers peace of mind while on the road.
