and now disc brakes,
made of either cast iron or nowadays ceramics ( very expensive ), these ROTORS or DISCS are attached to the wheels, the brake pads are placed in a BRAKE CALIPER which forces the pads against the rotor to produce friction and causes the wheel to slow/stop.
It is an english invention and it was patented in the 1902 by a william lanchester. The 1st production cars to appear with disc brakes were the Citreon DS and the Triumph TR3.
The design varies from solid cast iron to ventilated discs which are hollowed out, these hollowed out discs allow for easier dissipation of heat.
Holes were drilled into the disc brakes to prevent GASSING, brake pads when heated form gases and these gases create distance between the brade pads and brake rotors, these holes allowed gases to escape. This is called Cross Drilling. Cross drilling has the disadvantage that cracks can appear around the holes.
Slotted rotors work on the same principal as cross drilled rotors but they work better than the cross drilled rotors but they reduce brake pad life very much.
In racing and very high performance road cars other disc materials have been employed.Carbon-Carbon braking is now used in most top-level motorsport worldwide, reducing unsprung weight, giving better frictional performance and improved structural properties at high temperatures, compared to cast iron. nowdays companies like mclaren mercedese and ferrari and pagani use carbon-carbon brakes to increase braking efficency and to reduce brake fade.
The brake caliper is the assembly which houses the brake pads and pistons.
There are two types of calipers: floating or fixed. A fixed caliper does not move with the disc. It uses one or more pairs of pistons to clamp from each side of the disc, and is more complex and expensive than a floating caliper. A floating caliper moves with respect to the disc, along a line parallel to the axis of rotation of the disc; a piston on one side of the disc pushes the inner brake pad until it makes contact with the braking surface, then pulls the caliper body with the outer brake pad so pressure is applied to both sides of the disc.
Basically what happens when u press the pedal is that the pedal pushes a small lever which in turn pushes another small lever in the brake cylinder which multiplies the force and sends brake fluids into the brake lines. the brake line goes to each cylinder on each wheel and it compresses the piston of the brake caliper and as the piston is compressed it presses the brake pads against the brake discs and thus causes the car to slow down.