HD-40 Series directional vane rotors provide superior thermal stability and long service for asphalt late models, modifieds, open wheel, and most other types of high heat competition applications. All HD rotors are cast from premium grade, long grain carbon iron for long wear, high thermal stability and resistance to distortion. Thick wall pad sweep faces with directional cooling vanes provide superior heat absorption and dissipation qualities to prevent heat fade and realize long service life from the pads and rotors. All HD rotor faces are precision turned to less than .001" for flatness, parallelism, and run-out for smoother engagement and reduced vibration.