I forgot why to turn rotors. the brake pads need a nice smooth, non-directional finish in order to break in and thus, work properly. turn them too thin, they overheat. once turned they need to be washed with soap and water to remove all the grit and grease before installing them. brake clean doesn't do the job. once you clean them right, they will rust in the sunlight while drying. when they rust, they're clean.