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Difficulty: EasyBrake System Components Inspection

During a pre-trip vehicle inspection, you park on level ground, chock the wheels, release the parking brakes, and firmly pull on a manual slack adjuster by hand. What is the maximum distance the pushrod should move where it attaches to the slack adjuster?

  1. A
    No more than 1/4 inch
  2. B
    Zero movement because the pushrod must remain completely rigid
  3. No more than about 1 inchAnswer
  4. D
    No more than about 2 inches

Answer

No more than about 1 inch of pushrod travel is acceptable when pulled firmly by hand with the parking brakes released.
When checking manual slack adjusters on S-cam brakes with the vehicle secure, wheels chocked, and parking brakes released, pulling firmly by hand should result in no more than approximately 1 inch of pushrod movement at the attachment point.

Step-by-Step Solution

1
Identify the proper pre-trip inspection condition for checking manual slack adjusters.
The vehicle must be on level ground with wheels chocked and parking brakes released to allow manual movement.
Spring brakes must be released so the pushrod and slack adjuster can be moved freely by hand.
2
Evaluate the allowable manual pushrod travel limit against CDL safety standards.
Standard manual pull travel must not exceed approximately 1 inch (about 2.54 cm).
Movement exceeding 1 inch indicates excessive brake shoe-to-drum clearance or an out-of-adjustment slack adjuster requiring immediate service.

Key Concept

Manual slack adjuster pushrod travel inspection tolerances
Estimated Time:45s
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Topics

Brake System Components Inspection

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