The brakes may begin to squeak at about the 50 percent wear point. This is due to the size and material used for the brake pads and rotors. The brake rotor surfaces become uneven, causing a lip to form at the outer edge. This will generally require replacement of the rotors when the pads are worn (pad life varies depending on driving style and terrain).Google+
Car Problem Reports
Mercedes-Benz SL600 Replace Brake Rotors When Pads are Worn and Squeaking
Mercedes-Benz SL600 Problem
Average Mileage: 63,927 mi (44,578 mi - 102,000 mi)
Visitor, 1999 Mercedes-Benz SL600, 45,205 mi
Brakes work fine but after driving for a while slow stops and brakes squeak. Talked to brake store and 50% still good but I think i will replace rotors and pads anyway.
Visitor, 1999 Mercedes-Benz SL600, 44,578 mi
have not fixed problem, just purchased vehicle. Did have problem checked and brakes were ok'd but maybe need to be changed at 45,000 miles even if not worn.