CDL Air Brake Brake Adjustment and Maintenance

Question 1

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

Accepted Answer

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

Answer

To adjust air pressure delivered to the brake chambers

Answer

To regulate the governor cut-out pressure

Answer

To control air flow to the spring brakes

Question 2

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

Accepted Answer

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

Answer

Whatever the driver feels is sufficient based on pedal feedback

Answer

3 inches maximum for all brake chamber sizes

Answer

4 inches maximum for all brake chamber sizes

Question 3

What is an automatic slack adjuster (ASA)?

Accepted Answer

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

Answer

A device that automatically adjusts the governor cut-out pressure

Answer

An ABS component that adjusts brake pressure during skids

Answer

A computer-controlled system that monitors brake temperature

Question 4

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

Accepted Answer

Visually inspect and check push rod stroke to verify proper adjustment

Answer

Nothing — automatic adjusters require no inspection whatsoever

Answer

Manually adjust each slack adjuster to the desired setting

Answer

Replace all brake linings at each inspection interval

Question 5

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

Accepted Answer

¼ inch for drum brakes

Answer

⅛ inch for drum brakes

Answer

¾ inch for drum brakes

Answer

There is no minimum — replace only when brakes stop working

Question 6

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

Accepted Answer

Lining is contaminated with oil or grease

Answer

Lining has been in service for more than 6 months

Answer

Lining color has changed from its original appearance

Answer

Vehicle has traveled more than 50,000 miles since last replacement