About Those “Warped” Brake Rotors

I just completed a brake repair job on a 1992 Lincoln Town Car. This particular car has been very well maintained by its owners, and they weren’t really sure what to do when they suddenly began to feel a shimmy in the steering wheel during braking, along with a pulsing in the brake pedal.

Pretty scary. By now, you may have guessed the problem: Warped brake rotors. I get asked about this problem quite often, so I decided to discuss it here. To be correct, disk brake rotors

generally do not actually “warp”. What most commonly happens is that material from the brake pads is superheated and then transferred to the surface of the rotor, which is itself very hot, and this material is then fused onto the rotor surface at random places. This creates high spots or “bumps” on the otherwise smooth rotor surface, and these bumps are felt as vibrations whenever the brakes are applied. These vibrations are transmitted throughout the car and are usually felt very strongly in the steering wheel and the brake pedal.

So what usually causes brake rotor problems?

Well, the most common cause of this problem is overheating of the brake pads – i.e. “Riding the brakes” – or keeping the brakes applied too long when coming to a stop or slowing down. You can minimize the chance of damaging your brake rotors simply by not using the brakes for too long at any given time. When slowing down, apply the brakes in “spurts” rather than keeping the pedal down the whole time. This allows the pads and rotors to cool somewhat between applications. Other causes for this problem include defective or “sticky” brake calipers, which do not allow the brake pads to fully disengage from the rotor, and as a result they will overheat.

Okay, but how do I fix my warped rotors?

There are two ways to fix this problem:  1)you will either need to get your present brake rotors “resurfaced”, or 2)simply replace them with new ones.  In nearly all cases, the pads will need to be replaced with new ones. Don’t scrimp on this – cheap brake pads will generally fail noticeably sooner than higher-grade pads, and the price difference usually isn’t worth it.

To get your rotors resurfaced, you will need to remove them from the vehicle and take them to a place which can do the resurfacing work. Most major franchise parts stores such as NAPA, AutoZone, etc. can do this for you for a small fee. Many local shops can also do the work. Probably best to call ahead and ask if you’re not sure.

Not all used rotors can be resurfaced. In some cases you will need to buy new rotors. I generally use this option anyway because the cost difference is usually small. If you do buy new rotors, be sure to properly dispose of the old ones. You can usually take the old rotors to your local landfill and/or metal scrap yard. The scrap yard may even pay you for them.

After replacing the brake pads and either repairing or replacing the rotors, you should no longer feel a shimmy during braking nor any unusual movement in the brake pedal, and your brakes should be trouble free for many thousands of miles thereafter.