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 vehicles’ wheels. It’s essentially the heart of your car’s brake system. The most common vehicle uses of master cylinders are in brake and clutch systems. In brake systems, the operated devices are cylinders inside of brake calipers and/or drum brakes; these cylinders may be called wheel cylinders or slave cylinders, and they push the brake pads towards a surface that rotates with the wheel (this surface is typically either a drum, or a disc, a.k.a. a rotor) until the stationary brake pad(s) create friction against that rotating surface (typically the rotating surface is metal or ceramic/carbon, for their ability to withstand heat and friction without wearing-down rapidly).