Measuring a slack adjuster correctly is vital for ensuring proper functionality in a braking system. Follow these steps to gather the necessary measurements and identify the characteristics of your slack adjuster:
1. Count the Splines
- Locate the spline area of the slack adjuster where it connects to the camshaft.
- Carefully count the number of splines (teeth) on the camshaft opening. Common spline counts are 10, 28, or 37.
- This count helps determine compatibility with the camshaft.
2. Measure from the Center of Splines to the Center of Clevis Pin
- Position a measuring tape or ruler.
- Measure the distance between:
- The center point of the spline opening.
- The center of the clevis pin hole.
- This measurement is the arm length of your slack adjuster and is crucial for replacement or repair. Measurement A in the picture below.
- Some slack adjusters have multiple clevis pin holes to make them useful for multiple applications.
3. Measure the Spline Diameter
- Use a caliper or ruler to measure the diameter of the spline opening.
- Ensure the measurement is precise, as this ensures proper fit with the camshaft.
- Typical measurements are 1.25" and 1.5". Measurement C in the picture below.
4. Determine Whether the Slack Adjuster is Manual or Automatic
- Inspect the slack adjuster:
- Manual Slack Adjusters: Require periodic manual adjustment using a wrench.
- Automatic Slack Adjusters: Self-adjust with brake use, requiring less maintenance.
- This distinction is essential for ensuring proper adjustment and brake performance.
5. Note the Manufacturing Style
- Look closely at the design, shape, and any branding or markings on the slack adjuster.
- Compare it with reference images or manufacturing guides to identify the specific style or brand.
- This information can help you find an exact replacement or compatible model.
Additional Tips
- Always clean the slack adjuster and surrounding areas before taking measurements to improve accuracy. You also might get lucky and find a part number on your slack adjuster.
- Consult your vehicle’s manual for specific measurement tolerances and guidelines.
- If unsure, seek assistance from a professional mechanic to ensure safety and proper functionality.
By following these steps, you can confidently measure your slack adjuster and gather all the necessary details for replacement or troubleshooting.
Recommended Tools on Amazon
- Digital Caliper – Accurate readings of spline diameters.
- Tape Measure – Ideal for arm length measurement.
- Mechanic Gloves – Keep your hands clean and protected.
- Penetrating Oil – Loosen rusted or stuck adjusters.
- Adjustment Tool - Keep your brakes adjusted properly
- Grease - Don't forget to grease! Grease will dramatically improve slack adjuster life.
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