CDL Air Brake Brake Adjustment and Maintenance 2

Question 1

What is the purpose of the brake drum in an S-cam foundation brake system?

Accepted Answer

To provide a friction surface for brake shoes to press against to slow the wheel

Answer

The brake drum rotates with the wheel and provides the friction surface that brake shoes press against to convert kinetic energy into heat and slow the vehicle.

Question 2

When must a brake drum be removed from service and replaced?

Accepted Answer

When worn to the maximum diameter specification marked on the drum

Answer

Brake drums have a maximum diameter specification stamped on them — exceeding this reduces wall thickness and can lead to failure under braking stress.

Question 3

Why is a cracked brake drum considered a serious safety hazard?

Accepted Answer

It can fail catastrophically under the stress of braking, causing complete loss of braking on that wheel

Answer

A cracked brake drum can fail catastrophically under braking stress, potentially causing complete and sudden loss of braking on that wheel.

Question 4

What does it indicate if a vehicle pulls noticeably to one side when the brakes are applied?

Accepted Answer

One or more brakes on one side may be out of adjustment, worn, or defective

Answer

Pulling to one side when braking indicates unequal braking force, typically caused by a brake out of adjustment, contaminated lining, or a defective component.

Question 5

How should a driver verify brake adjustment during a pre-trip inspection?

Accepted Answer

With wheels chocked and 90 psi in the system, measure push rod stroke with brakes applied

Answer

With wheels chocked and air pressure at 90 psi, push rod stroke must be measured when brakes are applied and must not exceed the maximum for the chamber size.

CDL Air Brake - Commercial Driver's License Air Brakes Test Practice Test

CDL Air Brake - Commercial Driver's License Air Brakes Test Practice Test

CDL Air Brake Brake Adjustment and Maintenance 2