We should start off with a description of a
typical brake pad and and typical brake shoe. Let us first have a look
at the brake pad.
The material that you see as the grayish color with the split in the centre is the friction material and is what rides on the rotor. The split in the centre of this material is for noise reduction purposes.
The next item that we should discuss is the rotor. This is the round disc that the pads will apply pressure to in order to cause friction and bring the vehicle to stop. The rotor has two purposes. One is of course to give the pad something to press against to cause the friction needed for stopping and the other is to cool the brake pad during this process. Many rotors today have vents built into them for this purpose.
A typical brake rotor looks like the
picture to the left. Note that it has a very smooth surface for the
pads to apply pressure on and fins between the two sides for cooling purposes.
Now lets put it all together. The pads have to be held by something in order to press them against the rotors that we have described above. The item that applies this pressure is called a caliper. The caliper is an apparatus containing a piston the is pressurized with brake fluid by the master cylinder. A typical caliper might look like the one below.
You can see the
piston to the right and the brake pads already sitting inside the caliper.
The piston presses on them and with the rotor in between them applies
pressure causing enough friction to bring the vehicle to a stop.
Here is what it looks like when you put it
all together. As you can see the brake linings or pads are sitting
inside of the caliper which in turn is sitting over the rotor.
What takes place here is that the brake fluid is pushed from the master cylinder into the caliper and the piston in the caliper then squeezes the pads against the rotor.
The master cylinder is really nothing more than a reservoir mounted on top of a cylinder containing two plungers. When you apply pressure to the brake pedal you are pressing against those plungers and they in turn are pushing brake fluid through the brake lines. The fluid moving through the lines is not compressible and thus very much the same a sliding a metal rod through the lines and right into the caliper or wheel cylinder.
A typical master cylinder would like very much like what you see here. The reservoir on the top
of what appears to be just a metal tube is the reservoir for the brake fluid and the silver item that looks like a tube is the master cylinder on a typical vehicle of today.
Metal brake lines run from the master cylinder to the front
and rear of the vehicle. A typical brake line with fitting would look
like the one shown
here.
The metal line runs out to a proportioning valve and then continues on the
the wheel well area where it is linked to a reinforced rubber hose that
allows for movement of the suspension and steering components.
The proportioning valve adjusts the
flow
of brake fluid between the front and rear of the vehicle to prevent a
premature lock up at either end. This helps in reducing the
likely-hood of skidding on icy or slippery conditions.