Servicing disc brakes is normally a lot easier than working on drums. Rotors and calipers have fewer, larger parts than the average drum-brake system, so the average-skilled do-it-yourselfer can usually perform routine disc maintenance.
Rough Rotors
Replacing disc-brake pads is a story unto itself. This time the focus is on the inner surfaces of the disc-brake friction equation & the rotors. Although rotors routinely last longer than pads, they should still be checked at every regularly scheduled tire rotation. Over time, the friction that causes the car to stop will wear down the rotor's outer surfaces. Another possible rotor-destroyer is pads that are allowed to wear down to their metal rivets, which then cut grooves into the discs. Run your fingers across the rotor's contact area to feel for irregularities. Also, rotors that are allowed to overheat for extended periods of time can warp. This can cause the car to feel like the tires are horribly out of balance during braking. Most rotors have the minimum-thickness specification cast somewhere on their inner, non-friction area. Do-it-yourselfers can use a micrometer to determine if the rotor has enough meat or should be replaced. Run-out, or warping, can be checked with a dial indicator. It's even easier to have in-use rotors resurfaced on a brake lathe when changing the pads. Reputable mechanics will alert you to any problems and flat-out refuse to łturn˛ the rotors if they're too worn.
Installation Tips
- Wear a filtering mask when working on brakes brake dust can contain asbestos.
- Replacement rotors are often covered in Cosmoline,
a slippery, rust-inhibiting chemical. Use brake cleaner not petroleum-based solvents to clean rotors and all other brake parts.
- Keep grease, oil, and other lubricants off of the rotors' (and pads') friction surfaces. Clean these parts thoroughly when necessary.
- Newer vehicles might have electrical connections for the antilock brake system that need to be disconnected. Reconnect afterward.
- Calipers have to be removed from the vehicle to replace the rotors. Each caliper is typically secured with two bolts. Verify that you have the proper tool (sometimes an Allen wrench or even a large Torx bit) before beginning the job.
- Siphon some fluid from the master cylinder to prevent slosh-over when retracting the caliper pistons. Use a pump (not your mouth) and dispose of the old fluid properly. Never reuse old brake fluid. Top off the master cylinder after all components are back in place.
- Refer to a service manual for your vehicle for fastener torque specs and any specific requirements.
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