Brake pads and rotors are wear items and should be inspected regularly and replaced as necessary. It’s best to get in the habit of inspecting your vehicle’s brakes every 10,000 miles. However, if your brakes suddenly start to squeal or pull to one side, or if your brake pedal flutters when you step on it (not to be confused with the normal pulsing of ABS brakes when applied in a hard stop), you should inspect sooner.
Relining, caliper maintenance and disc grinding should be left to a professional. Brake components should be installed by a competent mechanic in a professional manner. Any incorrect installation of brake components can cause a major safety problem or an accident. If you are not a competent and qualified mechanic you should not attempt to install brake parts but should take the vehicle to a vehicle dealer or competent automotive mechanic for their installation. In some cases, servicing or replacing brake hardware at the time of pad or rotor installation may also be required.
Use the checklist below to inspect your disc brakes. If you're unsure about any of this, take your vehicle to a mechanic to have them checked out.
Loosen the lug nuts on the wheel you intend to take off. Jack up that end of the car and support it securely with jack stands. Remember to use wheel blocks for safety. Remove the wheel.
Look at the brake rotor but don’t attempt to remove it from the vehicle. Check the visible part of the disc for heavy rust, scoring or uneven wear. Rust generally is harmless unless the vehicle has been standing idle for a long time and the rust has really built up. If your disc is badly scored or worn unevenly, have a mechanic determine whether it can be resurfaced or needs to be replaced.
Brake rotors should be replaced before their thickness has reached the prescribed "Worn Rotor Minimum Thickness" limit (expressed in millimeters) engraved on the edge of the brake disc. Use a micrometer to measure rotor thickness.
Plain brake rotors can be turned on a brake lathe to remove scoring and to true the disc surfaces until this minimum thickness has been reached. Drilled and slotted rotors may or may not be able to be turned.
While you're looking at the rotor, spin it around with your hand. If you're looking at a drive axle, make sure the car is in neutral and the parking brake (if it's connected to that axle) is off. The rotor should turn more or less smoothly. If it grabs in one spot, it may be warped or have excessive brake pad deposits and should be machined or replaced. To better understand pad deposit issues, see Centric Parts' Technical Paper "The 'Warped' Brake Disc & Other Myths of the Braking System" & read "Myth 1: Brake Judder & Vibration is Caused by Discs That Have Been Warped from Excessive Heat."
If the vehicle has been driven recently, the caliper will be hot. If it’s cool, grasp it and gently shake it to make sure that it isn’t loosely mounted and its mounting hardware isn’t worn.
Look through the inspection hole in the dust shield on the caliper and look at the brake pads inside. Measure the thickness of the linings on the brake pads so that you can tell whether the linings on your brakes are badly worn. If the lining is down to the thickness of the steel backing plate, the pads should be replaced. Brake pads should typically be replaced when approximately 1/8" to 3/16" of friction material remains on the steel backing plate. If the linings have worn to the metal pads, the disc probably has to be reground or replaced as well.
The flexible rubber hose that runs between the steel brake line attached to the frame and the brake caliper should be dry (that is, not soaked in brake fluid or oil) and free of cracks.
Replace the wheel and lug nuts (these should be torqued to the manufacturer’s specifications) and hubcap. Lower the vehicle to the ground.
If the brake parts seem to be in good condition and your brake pedal doesn’t flutter when you step on it, you don’t need to do anything else.
Here's a video with step-by-step instructions on how to check your brake pads.