Brake discs, also known as rotors, are metallic circular components directly interfacing with brake calipers to generate frictional force and decelerate vehicle motion. Located on each wheel hub, they are integral to the vehicle’s braking system. Discs are typically constructed from cast iron, though carbon ceramic variations exist for high-performance applications. Key features include ventilated or solid designs for heat dissipation, and varying diameters, thicknesses, and surface finishes optimized for specific vehicle models. Surface condition, including runout and thickness variation, are critical parameters for proper braking performance and safety.