How to Replace Brake Rotors

It is important to know when and how to replace brake rotors as they are the most important component of a braking system. This article explains the concept of brake rotors and the procedure to replace them.
Whenever we check/change the brake fluid or we get new brake pads, we tend to forget the vehicle's brake rotors. They are as important as any other part of the braking system of an automobile. On application of the brakes, the pads are squeezed into the rotor, thus reducing its speed, which in turn haults the vehicle's spinning wheels, bringing it to a stop. Due to the wear and tear of the rotors, there arises a need to replace them. Before we learn about the procedure of replacing rotors, it is important to know the fuctioning of the rotors and when to replace them.

The Concept
The basic principle of disc brakes is to convert kinetic energy of the rotating wheel into thermal energy by friction. The two most important components of the disc braking system are the pads and the rotors. These are made of a high friction material. When the pedal is pressed, a hydraulic mechanism makes a caliper, and clamps the two pads together on the rotating rotor disc, thereby stopping the wheel's rotational motion and stopping the car. Thus, we can see that a rotor is aligned on the same axis as the wheel itself and the pads which act directly on the rotors, act indirectly on the wheel.

The factor that decides the working of the brakes is the metallurgical composition of the rotors and its design. This property determines the strength, noise, wear and tear, and most importantly its braking characteristics. Rotors are mostly made of high quality cast iron. The casting process is very closely monitored, and it is ensured that the rate at which the iron cools is high. The casting is done in a way so as to achieve correct tensile strength and hardness.

When to Replace
It is time to replace the rotor parts when they are worn down to the minimum specified limit also known as discard thickness. Rotor thickness should always be measured with a micrometer to get accurate measurements. They should also be changed if they have hard spots. Hard spots can return even if the rotor has undergone resurfacing. Squealing is another sign that it is time to change the rotors. In such cases, a loud noise or high pitch squeal can be heard on application of brakes.

The Process
The rotors normally last much longer than the pads, which require frequent replacement. Always wear a filtering mask during the process. This is necessary as brake dust contains asbestos.
  1. To start with, jack up the car and remove the wheels.
  2. Check the rotor for any wear and tear. Track marks or thinning out of the rotor would mean it is time for replacement.
  3. Using a large C-clamp, compress the brake calipers by placing the two sides of the clamp on either side of the caliper.
  4. Take out the bolts holding the caliper in place. Be careful not to disturb the line containing the brake fluid.
  5. Now, with the calipers removed, you can easily pull the rotor straight back outwards along the axis. In case it does not come out smoothly, due to the accumulation of rust, you have to twist and pull the rotor simultaneously from the rear until it gives way.
  6. Get the new rotor, and place it so that it is seated against the axle plate. Change the brake pads along with the calipers in their earlier positions by slipping the caliper back above the rotor, as it was before removal. Reinstall and tighten the bolts that hold the caliper tightly.
  7. New rotors are often covered in Cosmoline, which is a slippery anti-rust chemical. Use specially made cleaners to siphon off this chemical. Make sure that you don't use petroleum-based solvents. Always ensure that when you change the rotor on one wheel, do the same on the other wheel as well.
Your vehicle is now ready for a test drive. Drive very gently while testing the new replacement, as any fault or misfitting, will be revealed at this time.

Hope the above information proves immensely beneficial for you and your car. Remember, the brake is a very vital car part, and proper care should not be compromised with.