What is the function of the brake master cylinder in a vehicle's braking system?

• A. Stores brake fluid in reserve
• B. Converts pedal movement into hydraulic pressure to apply brakes at the wheel calipers or wheel cylinders.
• C. Regulates brake rotor temperature
• D. Measures pedal position for ABS

Answer: (B)

The brake master cylinder is the part that turns the force you apply to the brake pedal into hydraulic pressure in the brake lines. When you push the pedal, a piston inside the master cylinder moves and pushes brake fluid through the system. That hydraulic pressure travels onward to the wheel calipers (for disc brakes) or wheel cylinders (for drum brakes), causing the pads or shoes to press against the rotors or drums and slow the vehicle. The reservoir attached to the master cylinder stores the brake fluid and keeps the system topped up, and many setups use dual circuits for safety. ABS uses sensors and a control module to modulate pressure, not the master cylinder’s basic function.