Due to the size and material used on the brakes of these vehicles, the brakes may start to squeak around the 50 percent wear point. The brake rotor surfaces become uneven, causing a lip to form at the outer edge of the rotor. Because of this, the rotors are usually replaced when the pads are worn (pad life varies depending on driving style and terrain).Google+
Car Problem Reports
Mercedes-Benz SLK230 Replace Brake Rotors When Pads are Worn and Squeaking
Mercedes-Benz SLK230 Problem
Average Mileage: 71,000 mi (14,000 mi - 128,000 mi)
Visitor, 1999 Mercedes-Benz SLK230, 128,000 mi
Pads only about 1/2 worn, but started squeeling low speed stops. Rear brakes had pads replace and 9 months later started doing the same. Its worth it to buy top end pads and new rotors on this car - if the pads do not have tapered edges - they will squeek.
Driving down road, squeaking noise starts from Right Side, sounded like coming from tire area. Had in shop while under warranty, they said they could not find anything...now out of warranty, they want me to take it back in.
Visitor, 2003 Mercedes-Benz SLK230
Breaks squeaking; rotors and pads replacement