Drum Brake Basics
What is the primary function of drum brakes?
To slow down or stop the vehicle by converting kinetic energy into heat energy.
What component transfers hydraulic pressure to the brake shoes?
The wheel cylinder.
How is braking force applied in a drum brake system?
Hydraulic pressure from the master cylinder pushes the wheel cylinder pistons, which force the brake shoes against the drum.
How often should drum brakes be inspected?
At least every 12,000 miles or as specified by the vehicle manufacturer.
What could cause a spongy brake pedal?
Air in the brake lines.
What are the two main types of drum brakes?
Leading/trailing shoe and twin leading shoe.
What is the function of the brake drum?
To provide a surface for the brake shoes to press against, creating friction to stop the vehicle.
What happens when the brake pedal is pressed?
Hydraulic fluid is forced through the brake lines to the wheel cylinders, causing the brake shoes to expand and contact the drum.
What is a common sign that drum brakes need servicing?
Squealing or grinding noises when braking.
What might cause uneven braking?
Worn or contaminated brake shoes or drums.
What material is commonly used for drum brake linings?
Asbestos-free friction material.
What are brake shoes typically made of?
Steel with a friction material lining.
What is the effect of brake shoe wear on braking performance?
It can reduce braking efficiency and increase stopping distances if not properly adjusted.
What should be checked during a drum brake inspection?
Brake shoe thickness, drum condition, and the operation of the adjuster mechanism.
What is a possible cause of brake drag?
A stuck wheel cylinder or improperly adjusted brake shoes.
What is the purpose of the return springs in a drum brake system?
To retract the brake shoes away from the drum when the brake pedal is released.
What is the role of the adjuster mechanism in drum brakes?
To maintain the correct distance between the brake shoes and the drum.
How does the leading shoe in a drum brake system differ from the trailing shoe?
The leading shoe is pushed into the drum by the rotation of the wheel, increasing braking force, while the trailing shoe is pulled away.
How can you tell if a brake drum needs to be replaced?
If it is scored, cracked, or worn beyond the manufacturer’s specifications.
What could cause a pulsating brake pedal?
A warped brake drum.
How does the self-adjusting mechanism in drum brakes work?
It adjusts the position of the brake shoes to compensate for wear, ensuring consistent braking performance.
What component helps to dissipate heat generated during braking?
The brake drum, often with cooling fins.
What is the purpose of the parking brake in a drum brake system?
To hold the vehicle stationary when parked, typically by mechanically actuating the brake shoes.
What is the procedure for adjusting drum brakes?
Manually adjust the star wheel until the brake shoes lightly contact the drum, then back off slightly to ensure free rotation.
How can you diagnose a brake fluid leak in a drum brake system?
By inspecting the wheel cylinders, brake lines, and connections for signs of fluid leakage.