What is the recommended finish for late model rotors?
Most new OEM rotors today have a surface finish between 30 and 60 inches RA (roughness average), with many falling in the 40 to 50 RA range. Some OEM specifications say that anything less than 80 RA is acceptable. It?s almost impossible to see or even feel much of a difference between an 80 RA finish and a 40 RA finish. But such differences can, and do, affect brake performance ? and smoother is always better. Achieving a smooth finish requires sharp lathe tools and proper cutting speeds. Cutting rotors too quickly to save time may produce a surface finish that?s too rough and noisy. If you can feel grooves on the surface of the rotor with your fingernail, the rotor is probably too rough.
