There are two types of calipers, floating or non floating.

Calipers are generally made from three common casting metals: magnesium, aluminium and cast iron. Calipers are made of different materials, the most common are aluminium and cast iron.

The material used in the calipers becomes important to help eliminate deflection as deflection results in a spongy pedal.

The modulus of elasticity is very important to eliminate the deflection (flexing) of the caliper. The higher the modulus of elasticity number, the greater resistance to flex. Magnesium has a modulus of 6.5 million, aluminium has a modulus of 10 million, cast iron has a modulus of 14.5 million and steel has a modulus of 30 million.

The floating design was designed by the car manufacturers essentially to make the calipers less expensive to produce. It successfully applies the physics principle of "for every action caused an opposite and equal reaction happens." With this in mind they eliminated the piston(s) on one side of the caliper. This floating caliper is not solidly mounted, but slides back and forth on bushings.

When braking force is applied, the piston pushes the brake pad on the primary side and the reaction is the rotor being squeezed from the force of the pad primary side allowing the horseshoe shaped caliper to slide on the bushings so the secondary pads are used to squeeze the rotor. The caliper has to be very rigid to retain low deflection or the principle will be lost. Cast iron and steel is used because of its' modulus number of 14.5 million and 30 million respectfully. This also increases the "sprung weight" and it retains the heat longer. The big advantage to the full floating design (single piston) is that if the rotor has a slight run out (wobble), the floating feature will compensate without creating any instability. The other advantage is the single piston design is easier to bleed. The disadvantages are it is heavier, retains heat, requires approximately 100 pounds of pressure more to "slide" the caliper and requires more volume of brake fluid due to the diameter of the piston. Floating designed calipers also come with 2 pistons that are on the same side.

Non floating calipers (ie. 2,4 or 6 piston) require a fixed mounting bracket. Most race applications use this type of caliper, because they are generally made of aluminium, which displaces the heat faster and requires both less pressure and less volume to operate. The floating design allows all the piston to be applied at the same pressure, because the pressure is equalised when pressure is applied, thereby allowing the rotor to be squeezed by opposing forces (piston on each side). Aluminium will displace heat 1.5 to 3 times faster than the cast iron or steel calipers. This is important when the rotors heat up to 1100 to 1200 degrees in a racecar. Don't forget brake fluid has a boiling point of 550 to 700 degrees F. We have come a long way from the old 1965 Corvette design calipers, current nonfloating calipers are easily rebuilt and even have thermo barrier type pistons that reduced the transfer of heat from the rotors.

OEM (floating) vs 4 piston (non floating): Most of the brake kits currently being sold are single piston OEM type calipers. In order for the caliper to squeeze the rotor it has to use a floating design, otherwise it would only apply pressure from one side to the rotor. Because of this design you loose approximately 100 psi. 4 piston calipers squeeze from both sides and are fixed (don't float), so they (4 piston) do not require as much pressure. The single piston caliper also requires more volume to work. The area of a 2 3/4" single piston caliper is 5.93 si VS the area of two (2) pistons on a 4 piston design of 3.53 square inches. (you only multiply by 2 piston to get the area because the other 2 pistons are being apply at the same time to squeeze the rotor, unlike the one piston design) anyway 5.93' si VS 3.53 is a big difference. Does the volume effect the braking? Yes, it has a great effect on the master cylinder volume that is required for ail 4 wheels. This will mean you will have to use a larger diameter master cylinder to meet the requirements of the calipers. The larger the master cylinder is the lower the pressure output.

Rotors come in various designs, but basically there are vented rotors and solid rotors. Rotors can be a one piece design with the hat or hub incorporated in the casting or the two piece design where the rotor is separate from the hat or hub. In this case the bigger the rotor the better. The bigger the diameter means it takes that much longer before the pad is in the same area during the rotation of the rotor.

On vented rotors the fins should be far enough apart to allow air to flow between the fins, but close enough together so it allows enough support for the rotor walls. There can be as much as six tons of force being applied during braking and you do not want any deflection. Some vented rotors have curved fins to allow better flow of air and maximising the transfer of heat. Don't forget these rotors can get up to 1,200 degrees F, so anything you can do to assist the transfer of heat is a plus. If you have ever watched a NASCAR short track race with the camera on the rotors, you will know how hot they get.

Solid rotors should never be used on a car weighing over 2,800 pounds. These were designed for light duty and never used on a vehicie where heavy braking is needed. These rotors serve a specific need and work very good under limited conditions.

Your better designed brake systems will have the rotor separate from the hat or hub. This allows the rotor to have a uniform temperature across the rotor (remember the NASCAR rotor?). By having this uniformity it minimises the warping and cracking. Wilwood for an example uses an aluminium hub in the front, which the rotors bolt to. This allows the hot rotor to cool at the same rate throughout the rotor, because it is made of different material and it is a separate part. The aluminium hub is also designed to displace heat and keep it away from the bearings (remember the modulus of elasticity number is 75 percent that of cast iron, meaning it will displace heat at a faster rate). Having a two piece design also prevents the storage of this heat compared to a one piece cast iron rotor. Calipers also benefit by having less heat transferred to them and it assists to keep the brake fluid under the boiling temperature.

Factories use a one piece design, incorporating the hub/hat with the rotor; this was done strictly for cost.

Notice that the hub and rotor is cast as one piece. This does not allow for the uniform distribution of heat and it is high prone to warping and cracking due to the differences in temperature between the rotor and hub area. The one piece cast iron rotor will also retain heat longer, thereby transferring excessive heat to the calipers and brake fluid. The only advantage to the one piece design is initial cost. Did you really save any money?