Brake rotors are metal discs that are attached to the axles of a vehicle. When the driver pushes the brake pedal, the brake pads press on the rotor, creating friction, which forces the wheels to turn slower. That friction also causes the disc to wear out, and to need resurfacing (turned). But, the brake rotors may need to be replaced due to damage or excessive wear below a specified limit, how soon depending on miles driven and driving conditions (heat, dirt, sand, rocks, road salt, etc.).
1.Removing the Old Rotor

Put on protective gloves. Before performing any work on your vehicle, as you're gathering all the tools you'll need, it's a wise idea to find a pair of sturdy work gloves. Vehicle maintenance can be a messy job, so you'll want to protect you hands from grease and grime before working on the vehicle. These gloves can also protect your hands in the event of an accident.

2.Raise the vehicle with a lift or jack on solid level ground.
Loosen the lug nuts a little before lifting a wheel, if using a jack (the ground holds the wheels from turning while using your lug wrench). Block the other wheels to prevent the vehicle from rolling when lifting only one wheel, or only one end of the car, at a time. You may need to release the parking brake for the wheels you are servicing. Using hand tools and a hand-operated jack(s) works fine, but using a power impact wrench and/or a hydraulic car lift such as professionals use is easier.

3.Remove the vehicle's wheel.

4.Remove the calipers.

5.If necessary, loosen and remove the caliper mounting bracket bolts.

6.Remove the brake rotor.

7.Inspect grease seals and bearings, if your vehicle has a rotor with a grease packed bearing in the hub assembly, since removing the hub will likely damage the grease seal, and replacing the wheel bearings including bearing races can be insurance against a potential failure late

Installing a New Rotor