Mercedes-Benz W123 brake pads and brake discs
What are the W123 brake disc size and minimum thickness?
The front disc diameter is 278 mm. The thickness of a new rear disc is 10 mm (model years 1976–85) and the recommended minimum thickness is 8.3 mm. Brakes are safety-critical, so have a workshop check the result of the work.
Why do new brake pads drag or squeal on a W123 after replacement?
The most common cause is a seized piston or dirty, stuck caliper sliding surfaces. Clean the end surfaces of the pads, the sliding surfaces and the piston dust boots, and make sure everything moves freely. A blocked brake hose can also keep the brake applied. If there is a ridge at the edge of the disc, the ends of the pad friction surfaces are filed so that the pad sits evenly.
Why does the W123 brake pad wear light flash after fitting new pads?
The wear sensor wire may touch the brake disc and short to earth, so the light flashes as the wheel turns. Check the wires and connectors. The wear light is a different light from the one indicating low brake fluid.
Why do the W123 brakes vibrate when braking even though the pads and discs are new?
A loose wheel bearing or a loose track rod end can cause brake vibration, and a warped disc emphasises it. Check the bearings and steering joints. Brakes are safety-critical, so a workshop should check the result.