The ability of the Saab disc brake pads to turn to dust when they are pressed against the rotors on your vehicle is the only reason no damage occurs when the brakes are applied by the driver. The materials that the Saab brake pads are created from include a mix of ceramic, organic, or fine metallic ingredients. All of them are relatively hard materials which is why they can last for thousands of miles. The hardness of the disc brake pads is not as high as that which is used in the construction of the brake rotors that the pads make contact with. This is why the brake pads will wear and turn to dust when the friction is created in the braking procedure of your Saab. As the disc brake pads wear down from the friction that is created, the piston in the brake caliper moves outward. This is to compensate for the amount of pads that are being turned to dust in a one to one ratio. Since the piston in the Saab brake caliper is moved by hydraulic fluid that originated in the brake master cylinder's reservoir, this level of fluid in reserve begins to drop. The reservoir is large enough to handle this lowering of the hydraulic fluid and the reason additional brake fluid does not have to be added to the system if no leaks are present in between brake jobs. If hydraulic fluid is added to the reservoir instead of the Saab owner having their vehicle taken to the repair shop for the disc brake pads to be replaced, chances are the pads will totally wear out. This is when the metal backing plate the pads are mounted to will come in contact with the brake rotors and cause damage to both braking components.