The brake master cylinder is a component in your car’s braking system that drives the pressure generated by the brake pedal to the braking mechanism at your vehicle’s wheels. It’s essentially the heart of your car’s brake system. When you press down on the brake pedal, that force pushes a piston through the brake cylinder, converting the force into hydraulic pressure. This pressure pumps hydraulic fluid through the brake lines, transmitting pressure to a secondary cylinder at each wheel’s braking mechanism. The secondary cylinders drive the caliper piston to engage the brake calipers in disc brakes (the wheel cylinder in drum brakes). This action then goes on to stop the wheel.