There are a couple of reasons why brakes will squeal.
One: Vibration. In other words, pads will always need a type of retainer. Most good company pads will supply a type of "Stop Squeal" with the pads. Others like to use a shim (Our pads like shims) This vibration, when applying your brakes, will transfer into a form of a chime. Most call it the CITY BUS symdrome.
Cure: As dmjarosz stated; Pep Boys, Autozone, NAPA, and other automotive parts companies carry in-stock anti-squeal and shim kits. ONLY APPLIED TO THE BACKING PLATE OF THE PAD, the squeals usually go away.
Two: Glazed Friction Surfaces. Not as common, but still possible. Glazed friction materials such as the contact surface of the pads, or the contact face of a rotor, could very much cause a squealing when both surfaces meet. Like I said, not as common but very much possible.
Cure: Most think, once the rotor is resurfaced, the squealing will go away. WRONG! A Rotor must be resurfaced, then have a non-directional swirl pattern applied to it's contact face. Easily performed while on the brake lathe, apply a peice of sand paper to the contact face (Attach the piece of sandpaper to a piece of wood, this makes it so your fingers are away from the contacts of the brake lathe.) move the peice of sand paper in an up and down motion. Please be careful!
Like Paul Nimz stated, use quality pads. Ford, Hawk, and Other types of Carbon Metallic Pads are the way to go.
Good Luck! I hope this helped you.
Sal
