This is the single-piston...
This is the single-piston Kelsey-Hayes disc brake used on the Mustang from 1968-up. The most significant change to this brake came in 1970 when Ford gave it a larger spindle. Look for the large-spindle disc brake on 1970-87 Mavericks and Comets, and 1975-80 Granadas and Monarchs. Parts and complete systems are available from Master Power Brakes as well.
Disc Brakes
There has always been a more sophisticated, upscale attitude about disc brakes. For one thing, disc brakes outperform drum brakes by a wide margin. Disc brakes dont fade. Disc brakes are simple compared to drum brakes. Disc brakes tolerate hard braking better than drums.
To understand how a disc brake works, we have to understand the design. First, we have either floating or fixed caliper disc brakes. Then we have one-, four-, or six-piston calipers. Disc brake caliper pistons do the same thing wheel cylinder pistons do in a drum brake. They transfer fluid pressure to the friction material that stops us. The more pistons we have in a disc brake, the better. First generation Mustang disc brakes (1965-67) have four-piston disc brake calipers. This means we have four pistons transferring pressure to brake pads on both sides of the rotor. A four-piston disc brake applies more uniform pressure to a brake rotor.
From 1968-up, Ford went to a single-piston, floating caliper disc brake that became a mainstay on Fords for many years. One large piston transfers fluid pressure to brake pads on both sides of the rotor. Because the caliper floats, pressure is applied to both sides of the rotor. Simply put, the caliper squeezes the rotor.
 This is a first generation...  This is a first generation Mustang four-piston disc brake exploded view. Because four-piston disc brake calipers apply more uniform pressure to the pads and rotors, they make the best disc brakes. The only down side is sticking pistons. Stainless Steel Brakes Corporation has solved this problem by replacing original cast pistons with stainless steel pistons, which will not corrode. |  This cross-section of a four-piston...  This cross-section of a four-piston caliper shows us whats inside. Two pistons on each side transfer brake hydraulic pressure to a brake pad on each side. Think of a disc brake like you would hand brakes on a bicycle. Hand brakes squeeze the bicycle wheel, bringing us to a stop. Brake calipers squeeze the spinning rotor, with the same result. |  This closeup of disc brake...  This closeup of disc brake caliper piston seals shows what happens under pressure when we apply the brakes. |