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| Dial Indicator | A precision measurement tool used to measure small distances or variations in dimensions. In the context of disc brakes, it is commonly used to measure runout, thickness variation, and other critical dimensions. |
| Disc Brake Micrometer | A specialized micrometer designed for measuring the thickness of brake discs. It provides accurate measurements to determine if the disc is within the manufacturer's specified thickness tolerance. |
| On-Car Lathe | A machine used to resurface brake discs while they are still mounted on the vehicle. It allows for precision machining of the disc to remove surface imperfections and restore parallelism for improved braking performance. |
| Parallelism | The condition in which two surfaces, such as the braking surfaces of brake discs, are perfectly aligned and equidistant from each other. Proper parallelism ensures even contact between the brake pads and the disc, resulting in efficient braking. |
| Piston Retraction Tool | A tool used to retract the pistons in a brake caliper when servicing disc brakes. It applies pressure to the pistons, pushing them back into the caliper housing to facilitate the installation of new brake pads or rotor. |
| Pulsation | A vibration or throbbing sensation felt in the brake pedal or steering wheel during braking. Pulsation is often caused by uneven brake disc wear, thickness variation, or lateral runout, resulting in inconsistent braking performance. |
| Rough Cut | The initial pass of a machining process, such as brake disc resurfacing, to remove surface imperfections and excess material. It prepares the disc for a final finish to ensure smooth and even braking surfaces. |
| Lateral Runout | The side-to-side movement or deviation of the brake disc from its true rotational axis when spinning. Excessive lateral runout can cause brake pulsation and uneven pad wear, affecting braking performance. |
| Taper | A gradual decrease or increase in thickness or diameter along a surface, such as the braking surface of a brake disc. Taper can affect brake pad wear and braking efficiency if not within acceptable tolerances. |
| Thickness Variation | The difference in thickness between different areas of the brake disc's braking surface. Excessive thickness variation can cause brake pulsation and uneven braking, requiring resurfacing or replacement of the disc. |
| Wear Indicator | A feature on brake pads that alerts the driver when the pads have worn down to a certain level. It is typically a metal tab or groove that contacts the disc surface, producing a squealing noise to indicate the need for pad replacement. |
