We should probably start by saying a Brake Master Cylinder technically is not essential. You could use cable-actuated brakes, if you liked, like the cheap items you get on entry-level mountain bikes. On the other hand, to stand the strain of stopping one or two tonnes of metal, plastic and humans over 10-20 years, the cable would have to be massive. 

Picture a brake pedal in your mind. Delve into the relative darkness of that imaginary footwell and push that pedal with your mind foot. In most cars the pedal motion directly pushes a rod (known, funnily enough, as a pushrod) into one end of a sealed Brake Wheel Cylinder filled with fluid, two pistons to displace the fluid, and springs to push back against the main force and return the brake pedal to its resting position when released. 

Above the Clutch Master Cylinder, which is normally horizontal, is a vertical fluid reservoir. Its job is to make sure no (compressible) air gets into the system by retaining enough spare fluid volume to keep the system fully fed at all times and in all phases of its operation.

When the pedal is pressed, the piston in the Clutch Wheel Cylinder is pushed in forcing hydraulic fluid from the master cylinder through the tube and hose to the slave cylinder (on the left). The fluid pushes the slave cylinder piston toward the open end of the cylinder pushing the pushrod that connects to the lever on the clutch-operating shaft that in turn releases the clutch.

Manual transmissions are far from dead on the street, but late-model, overdrive six-speeds often demand a late-model hydraulic clutch release system as opposed to a mechanical system. This story will look at some of the basics for hydraulic clutch actuation. The system—similar to a car's hydraulic braking system—uses a hydraulic master cylinder to create line pressure plumbed (usually) to an internal Hydraulic Clutch Bearing positioned on the transmission's input shaft. 

What Is A Brake Hose?

A Brake Hose is a vital brake component responsible for delivering brake fluid from your vehicle’s master cylinder to the wheel cylinder (in drum brakes) or brake caliper (in disc brakes).