Examkin

Question

Difficulty: MediumBrake System Components Inspection

After securing a tractor-trailer on level pavement with wheel chocks and releasing the cab parking brake control valve, a technician pulls firmly by hand on the manual slack adjuster at each wheel position. What is the maximum distance the pushrod should move from the brake chamber to be considered within safe operational tolerance?

  1. A
    Up to 1.5 inches of movement when tested with the parking brakes set
  2. No more than 1 inch (approximately 2.54 cm)Answer
  3. C
    Exactly 1/4 inch, measured with the service brake pedal fully depressed
  4. D
    No more than 2 inches, provided the spring brakes remain fully engaged

Answer

No more than 1 inch (approximately 2.54 cm)
Under standard commercial vehicle inspection criteria, manual slack adjuster free play is checked by chocking the wheels, releasing the parking brakes, and pulling hard by hand on each slack adjuster. Safe operating tolerance permits no more than approximately 1 inch of pushrod travel at the clevis attachment point.

Step-by-Step Solution

1
Identify the proper vehicle configuration for checking manual slack adjuster free play.
The vehicle must be parked on level ground with wheels chocked and parking brakes released so the pushrod is free to move manually.
Spring brakes hold the pushrod tightly in the applied position, making it impossible to check manual free play if left set.
2
Determine the maximum allowable free play travel when pulling the slack adjuster by hand.
The pushrod must not move more than approximately 1 inch at the point where it connects to the slack adjuster.
Movement exceeding 1 inch indicates excessive clearance between the brake linings and the drum, requiring mechanical adjustment.

Key Concept

Manual slack adjuster free play inspection tolerance and procedure
Estimated Time:1m 0s
Rate this question

Topics

Brake System Components Inspection

More questions from this topic