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Zorluk: OrtaBrake System Components Inspection

An operator completes an end-of-shift post-trip inspection and examines the wheel-end brake assemblies and air lines on a heavy combination unit. Which finding represents an acceptable operating condition rather than a safety defect?

  1. A
    A manual slack adjuster pushrod moves 1.5 inches when pulled firmly by hand while the parking brakes remain applied.
  2. Brake shoe linings on an S-cam foundation brake measure 5/16 inch in thickness at the center with clean friction surfaces.Cevap
  3. C
    A brake drum exhibits a structural crack that extends across two-thirds of the width of the friction surface.
  4. D
    An air brake line shows localized friction wear that exposes the internal fabric reinforcement ply.

Cevap

Brake shoe linings measuring 5/16 inch in thickness at the center with clean friction surfaces represent an acceptable operating condition.
For commercial vehicle S-cam drum brakes, non-steering and drive axle brake shoe linings must be at least 1/4 inch (4/16 inch) thick at the center of the shoe and free of grease, oil, or physical damage. A lining measurement of 5/16 inch satisfies both thickness and cleanliness requirements.

Adım Adım Çözüm

1
Evaluate the regulatory wear limit for drum brake linings against the reported measurement.
The minimum legal lining thickness for S-cam drum brake shoes is 1/4 inch (4/16 inch). The observed measurement of 5/16 inch is above the minimum threshold.
Commercial vehicle safety standards require adequate friction material thickness to prevent metal-to-metal contact with the drum and avoid brake fade.
2
Assess the contamination status of the friction surfaces.
The linings are clean and free of grease or oil from leaking hub seals.
Oil or grease on brake friction materials causes severe slippage, uneven braking, and potential wheel fire.
3
Evaluate the remaining options against safety defect criteria.
Manual slack adjuster travel exceeding 1 inch, drum cracks exceeding half the friction width, and air hoses worn to the fabric reinforcement layer are all disqualifying safety defects.
Identifying acceptable versus defective components ensures compliance with Federal Motor Carrier Safety Administration (FMCSA) out-of-service standards.

Anahtar Kavram

Foundation brake component inspection standards, minimum friction material tolerances, and defect identification
Tahmini Süre:1m 0s
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Brake System Components Inspection

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