Which parts are included in service brake components?

• A. Chambers, diaphragms, and pushrods
• B. Calipers and rotors
• C. Master cylinder and booster
• D. Brake drums and backing plates

Answer: (A)

Service brakes use compressed air to create braking force through a brake chamber. The key parts here are the chamber, the flexible diaphragm inside it, and the pushrod connected to the piston. When air pressure enters the chamber, the diaphragm pushes the piston, and the pushrod transfers that motion to apply the brakes. This pneumatic actuator setup is what defines the service brake assembly.

Calipers and rotors are parts of a disc brake friction system, not the pneumatic actuator. The master cylinder and booster belong to a hydraulic actuation path rather than the air-driven service brake. Brake drums and backing plates are part of the drum brake assembly, which can involve different actuation than a brake chamber.