Disc brake calipers come in many sizes and configurations, including fixed-caliper, multi-piston designs, and the more modern floating-caliper, single piston designs that may also contain a mechanically actuated parking brake. Needless to say, disc brake calipers have undergone a series of design changes that continue to make them more adaptable to late-model import vehicle applications.

To illustrate, early racing and high-end vehicles used large-diameter rotor, multi-piston, fixed caliper designs that had enough swept braking area to stop the vehicle without using a conventional vacuum assist. Because modern imports are heavier and use smaller-diameter wheels than lightweight racing vehicles, caliper design has evolved from expensive multi-piston designs to the single-piston, hydraulic or vacuum-assisted floating caliper designs in use today.

CALIPER HYDRAULICS
Unlike drum brakes, disc brakes generate no servo effect and therefore must rely solely upon hydraulic pressure to force the brake pads against the rotor. Because a tremendous amount of pressure must be applied to the disc brake pad, the ratio between brake pedal and caliper piston travel is very big. A brake pedal travel of one inch, for example, may be required to move the front caliper pistons just a few thousandths of an inch.

The clearances between the brake pad and rotor are therefore very critical to establishing correct brake pedal height and...