Brake Disc


A complete inspection of the rotor, caliper, and pads should be done anytime you are working on the brakes. you should also check the wheel bearings.

Whenever you are doing brake work, thoroughly inspect the entire brake assembly. Courtesy of American Honda Motor Company, Inc.

Some brake shoe pads have wear sensing indicators. The three most common design wear sensors are audible, visual, and tactile.

Audible sensors are thin, spring steel tabs that are riveted to or installed onto the edge of the pad's backing plate and are bent to contact the rotor when the lining wears down to a point that replacement is necessary. At that point, the sensor causes a high-pitched squeal whenever the wheel is turning, except when the brakes are applied, then the noise goes away. The noise gives a warning to the driver that brake service is needed and perhaps saves the rotor from destruction. The tab is generally installed toward the rear of the wheel.

Operation of the wear indicator. Courtesy of Wagner Brake Products.
  1. Visual sensors inform the driver of the need for new linings. This method employs electrical contacts recessed in the pads that touch the rotor when the linings are worn out. This completes a circuit and turns on a dashboard warning light. This system is found mostly on imports.
  2. Tactile sensors create pedal pulsation as the sensor on the rotor face contracts the sensor attached to the lower portion of the disc pad.

When a pad on one side of the rotor has worn more than the other side, the condition is called uneven wear. If you are not sure the pads are worn enough to warrant replacement, measure them at the thinnest part of the pad. Compare this measurement to the minimum brake pad lining thickness listed in the vehicle's service manual, and replace the pads if needed.

Uneven pad wear often means the caliper is sticking and not giving equal pressure to both pads. On a sliding caliper, the problem could be caused by poor lubrication of or deformation of the machined sliding areas on the caliper and/or anchor plate. A slightly tapered wear pattern on the pads of certain models is caused by caliper twist during braking. It is normal if it does not exceed 11/48-inch (3mm) taper from one end of the pad to the other.

Normal pad wear pattern.