Braking Series...Part 2......Match Rotor To The Motor...

Cementite: Cast Iron is an alloy of iron and silicon in solution intersped with particles of carbon.At elevated temperatures,inclusions of carbides begin to form in the matrix.In the case of the brake rotors,any uneven deposits on the rotor surface become hotter than the surrounding metal. Every time that the leading edge of one of the deposits rotates into contact with the pad, the local temperature increases.When this local temperature reaches around 500 degrees celcius,the cast iron under the deposits begin to transform into Cementite . 

Cementite is very hard , very abrasive and is a poor heat sink. If severe use continues the system   will enter a self defeating spiral-the amount and depth of the Cementite increases with increasing temperatures and so does the brake roughness. 

Calipers: There are basically 2 types of design: fixed and floating..a fixed caliper is secured rigidly to the axle assembly and has at least 2 opposing pistons that force the pads against the rotor. A sliding or floating caliper has pistons only on one side of the rotor Therefore , when the caliper acts, it must slide or float in order to bring the pad on the opposite side in contact with the rotor.Nearly all original equipment calipers are of the floating type.In a system with fixed calipers,not only is the mounting much more rigid,but the stiffness of the caliper itself is greatly increased.This manifest itself in enhanced braking performance,pedal feel and pad wear. Performance calipers are usually made of cast aluminum.

Brake Torque: This is basically the clamping force of the braking system.The brake caliper acts on the rotor at a certain distance from the hub centre, known as the total piston area.(effective radius) The clamping force of a caliper is measured in pounds.The force exerted by the caliper (brake line pressure) , multiplied by the total piston area of the fixed caliper and two times the total piston area in a floating design equals the brake torque. Increasing either the brake line pressure (force applied by the caliper) or the piston area results in increased brake torque. Therefore a larger rotor allows for more clamp area resulting in better torque.Which also means just installing a larger rotor of any design or increasing the coefficient of friction (type of brake pad used) will not increase brake torque.

During braking, the front brakes provide about 70% of the stopping power hence, they also wear faster.This is because the heavy engine and transmission system is located in front , and when braking,the centre of gravity shifts towards the front thereby stressing the front pads and rotors.Adding a big brake system to the rear of the vehicle can result in unstable condition,and actually degrade braking performance. Smaller aftermarket slotted rotors are available for the rear. They work with your standard calipers and give you increased stopping powers,cooler operating temperatures,and reduced brake fade.The front should have a larger and more powerful braking system.

The friction materials of the brake pads and rotors must not come into contact with the greases as this could lead to brake failure. Check rotor thickness and replace if the wear limit is exceeded or if cracks are found.Remove any corroded areas or heavy surface crazing on the outer and inner parts of the rotor working  surface area by skimming the surface area. One of the most important steps after installing new rotors or pads is to bed them in,otherwise it can lead to improper wear and braking performance.

High performance models use larger rotors and 4 pot (for 300 to 335 mm rotors by up to 30mm thickness) or 6 pot (335mm to 378mm rotors by up to 32mm thickness) or 8 pot (380mm to 405mm rotors by up to 36mm thickness calipers to increase braking performance.There is also a 12 pot caiiper for the extreme car like the GTR R35. The stock rotors are mostly on the average about 26mm thickness based on a 330mm rotior size. The larger brake surface area provides more friction when braking so that you can stop on a dime.Enquire for service kits for after sales purchase that should include all replacement seals and bolts for long term maintenance.You can upgrade your brakes by using the braking components from a larger model.However, some modifications are required to mount them.Although many family saloons make do  with drum brakes for the rear and not disc brakes,the drum brakes provide more than adequate braking performance as 70% of the braking force is at the front.