Modern disc braking systems rely on brake pads and brake rotors (or discs) to function. The brake pads often take center stage since they are consumed more quickly under typical conditions, but your rotors are just as crucial. Failing rotors can impact your braking performance in a variety of ways, as well as create vibrations and unpleasant noises when you stop your car.
While brake pads usually have a predictable lifespan, your brake rotors typically don't require replacement on a regular schedule. This article will help you to understand when (and why) you should replace your rotors to keep your car's braking system functional, quiet, and safe.
Objective Data: Pad and Rotor Wear Specifications
If you routinely have your brakes inspected by a professional, then you can use objective data to determine both when your pads and your rotors require replacement. For brake pads, the minimum material thickness is 3mm. Once your brake pads have less than 3mm of friction material remaining, you should plan to replace them as soon as possible.
On the other hand, minimum rotor thickness will vary from manufacturers. This information should be available from your vehicle's manufacturer (if you are using stock rotors) or from the manufacturer of an aftermarket rotor. As long as your rotors have more material remaining than the minimum thickness guidelines, you can usually resurface your existing rotors rather than replace them.
Judgment Calls: Resurface or Replace?
Under normal driving conditions, brake rotors can last twice as long (or longer) than brake pads. Poor driving habits, such as riding your brakes or applying full pressure at all times, can shorten the life of your rotors. Likewise, you can wear down your rotors much more quickly by driving on old brake pads, since the friction material will eventually wear away and expose the rotors to metal-on-metal contact.
When you abuse your rotors in this way, you usually create scoring and warping on the surface. This damage can cause your brakes to grind, pulsate, and generally perform poorly. You can repair your rotors by resurfacing, but only if the rotors will remain above their minimum required thickness after the process.
In many cases, resurfacing is not a cost-effective option. Replacement rotors are relatively cheap, and rotors often require replacement with every other brake pad replacement. Resurfacing your rotors may save you money upfront, but they will still ultimately require replacement in the future. In general, you should choose to replace your rotors by a disc brake service once they become worn enough to affect your car's driveability.