I was told that those are machined to get surface glaze removed and any imperfections. I don't understand also. I complained about my brakes squealing in Sept. They machined the rotors, left the ceramic pads and charged me $100.00 among other things. I complained in Oct. and they again machined the rotors and replaced the frt pads with motorcarft and charging me 164.99 + disposal fee...plus additional work. I had to take the car in this past Monday because some yahoo broke in through the drivers lock and I agin complained the brakes were still squealing. They tried to charge me another 164.99, but I had gone to their website prior and printed off the coupon that did not state the price was per axel. So they said they would honor it. Well, by the time I returned to work, they had removed that coupon from their site. They called and said they also had to replace the ball joints. (covered by my warrenty)
Today they called and the total price of this visit. $512.24. Brakes free, Ball joints - $100.00, replacing the driver door cyclinder, rekeying, and labor. $412.24!!!!
That car better run and ride like a dream now!! I've spent over $1000.00 in 3 months. I don't mind spending that amount of money, but I better have brakes that don't squeal!!!!!!