Brake Adjustment and Maintenance Flashcards

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

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

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.

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

Answer: When worn to the maximum diameter specification marked on the drum

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

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

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

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

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

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

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

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

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

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.

What is a 'brake spider' in an S-cam drum brake system?

Answer: The fixed mounting bracket attached to the axle that supports brake shoes and foundation brake components

The brake spider is the fixed mounting bracket attached to the axle flange that supports the brake shoes, anchor pins, and other foundation brake components.