Brake Adjustment and Maintenance Flashcards

What is the purpose of a slack adjuster in an air brake system?

Answer: To maintain proper brake shoe-to-drum clearance as brake linings wear

Slack adjusters maintain proper clearance between brake shoes and drum as lining wears down, ensuring the push rod does not have to travel too far.

What is the maximum push rod stroke allowed before brakes are considered out of adjustment?

Answer: Varies by brake chamber size, but typically 1¾ to 2 inches maximum

Maximum push rod stroke limits vary by brake chamber size but are typically around 1¾ to 2 inches — exceeding this means brakes are out of adjustment.

What is an automatic slack adjuster (ASA)?

Answer: A self-adjusting mechanism that maintains proper brake adjustment without manual intervention

An automatic slack adjuster continuously self-adjusts to maintain proper brake lining-to-drum clearance without requiring manual adjustment.

Even with automatic slack adjusters installed, what must a driver do during pre-trip inspection?

Answer: Visually inspect and check push rod stroke to verify proper adjustment

Drivers must still visually inspect slack adjusters and verify push rod stroke during pre-trip inspections, as automatic adjusters can still malfunction.

What is the minimum brake lining thickness allowed on drum brakes before replacement is required?

Answer: ¼ inch for drum brakes

Brake linings must be replaced when they reach ¼ inch thickness on drum brakes to maintain safe stopping performance and prevent metal-to-metal contact.

What condition requires immediate brake lining replacement regardless of lining thickness?

Answer: Lining is contaminated with oil or grease

Oil or grease contamination on brake linings significantly reduces friction, making them ineffective and requiring immediate replacement.