BRAKE DISKS (ROTORS)

Brake disks are far less prone to brake fade than brake drums but they are not immune to brake fade. Thus converting the rear drum brakes to brake disks will greatly reduce brake fade but there is so much more that you can do to your brake rotors to optimize your brakes. If you have solid brake disks, replacing them with ventilated disks will improve the heat dissipation characteristics of the disks. You could also have the ventilated disks cross drilled or slotted. The holes in cross drilled brake discs help disperse heat and further reduces brake fade while slotted discs help to de-glaze the brake pads, ensuring better friction between the brake pad and the brake disc but they will wear the brake pads faster. Of the two, slotted brake disks tend to perform better than cross drilled brake disks but they transmit more vibration though the steering wheel and are noisier. You should also note that slotted brake discs are directional, in other words, the slots must turn in a particular direction. Brembo brake disks, for example should be installed so that the end of the slot nearest the outer edge of the disc comes into contact with the brake pad first but this may differ with other disk manufacturers. Make sure which way the slots should rotate and install them correctly.

Another option is to fit larger diameter brake rotors. A larger diameter brake rotor reduces the braking effort as it gives the caliper more leverage to stop the disc rotating and allows the car to slow down much quicker without causing too much build up of heat. However, there are two factors that limit the diameter of disc that you can use: the size of the wheels; and the relocation of the brake calipers. The wheel size will limit the size of the rotors but wheel may also limit the placement of the brake calipers, especially if you are using alloy wheels. This is important as when you fit a larger brake disk, the brake caliper must be mounted further away from the wheel hub. Thus, when fitting larger diameter brake disks you need to ensure that you can mount the brake caliper and that there is sufficient clearance better the caliper and the wheel.

here are two disadvantages of fitting larger diameter disks though. Firstly, when you retain the standard brake calipers, the area of the brake disk that comes into contact with the brake pads remains the same. This will result in rust towards the centre of the disc that will not be removed by the brake pad when you brake braking. If you fit a larger brake caliper then you remove this problem. Another disadvantage is that a larger diameter brake disc will result in an increase in the car's unstrung weight, which can adversely affect handling.

Source: http://www.custom-car.us/safety/brakes.aspx