How to Replace Brake Rotors

We check/change the brake fluid, we get new brake pads but we seldom look at a vehicle's brake rotors. They are as important as any other part of the braking system of an automobile. On application on brakes, the pads are squeezed into the brake 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 brake rotors, there arises a need to replace them. Let's see how to replace brake rotors and when.

Brake Rotors Explained

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 brake pads and brake rotors. These are made of a high friction material. When the brake pedal is pressed, a hydraulic mechanism makes a caliper, 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 brake pads which act directly on the rotors, act indirectly on the wheel.

The factor that decides the working of brakes is the metallurgical composition of the rotors and its design. This property of a rotor determines the strength, noise, wear and tear and most importantly its braking characteristic. Brake 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 rotors 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 accurately determine thickness. Rotors should also be replaced 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 brake rotors. In such cases, a loud noise or high pitch squeal can be heard on application of brakes. This is a sign that there is a need for changing the brake rotors or the brake pads.

The Replacement Process

Brake rotors normally last much longer than the brake pads which require frequent replacement. Here's a step-wise description of replacing them.

• Always wear a filtering mask while replacing brake rotors. This is necessary as brake dust contains asbestos.
• To start with, jack up the car and remove the wheels.
• Check the rotor for any wear and tear. Track marks or thinning out of the rotor would mean it is time for replacement.
• Using a large C-clamp, compress the brake calipers by placing the two sides of the clamp on either side of the caliper.
• Take out the bolts holding the caliper in place. Be careful not to disturb the brake line containing the brake fluid.
• Now, with 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.
• Get the new rotor, and place it so that it is seated against the axle plate. Replace 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.
• New brake rotors are often covered in Cosmoline, which is a slippery anti-rust chemical. Use specially made brake cleaner to siphon off this chemical from rotors. Make sure that you don't use petroleum-based solvents.
• Always ensure that when you replace the rotor on one wheel, replace the other wheel's rotor as well.

Your vehicle is now ready for a test drive with the brand new brake rotors. Drive very gently while testing the new replacement, as any fault or misfitting, will be revealed while testing.

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