by Tommy Lee Byrd and Kyle Tucker
(taken from Detroit Speed's How to Build a Pro Touring Car)
Offering clamping force on the brake pads, the calipers are another important component of the Pro Touring brake setup. Here’s how they work: A burst of brake fluid is sent through the lines when the brake pedal is pressed, and this fluid moves a piston, which pushes the brake pad closer to the rotor. The pads apply pressure to the rotor with enough force to bring the car to a halt. The caliper is mounted in a fixed location: For the front, it mounts to the spindle upright, and for the rear, it mounts to the rear-end housing. When disc brakes were first used on American automobiles, the calipers were clunky and inefficient, but they certainly outperformed drum brakes on all levels. As the years went by, caliper design evolved, providing better stopping power by increasing clamping force. What started as a single-piston design is now commonly available in four- and six-piston designs. Multiple pistons disperse the load evenly and provide a much larger clamping area than did the older designs.
Originally, brake calipers were made from cast iron. One of the biggest breakthroughs involved developing an aluminum caliper for high-performance applications. This reduces weight and offers a more efficient design to increase braking performance dramatically. Today’s aftermarket brake caliper, a Baer 6S unit for example, features stainless steel pistons with staggered piston sizing to minimize brake pad wear. These details, in combination with the extreme surface area, result in an awesome braking system that looks cool too. It’s hard to dislike the appearance of a big six-piston caliper tucked behind the spokes of a large-diameter wheel.
The heat dissipation, clamping force, and surface area are the main concerns of a disc brake caliper, so if you can order a brake kit that finely executes those details, expect to bolt it on and feel a big difference. A large rotor and a six-piston aluminum caliper go a long way to making your Pro Touring machine stop and handle like a modern sports car, but you must complete the brake system with matching components and accessories to make it all work in harmony.
Brake calipers have evolved over the years, and it’s common to see a Pro Touring car sport a set of six-piston aluminum calipers. What was once considered high end is now commonplace, but it’s still a very important part of a Pro Touring build. These Baer 6R calipers are a work of art and provide unmatched stopping power.
Caliper clearance is often an issue when using aftermarket braking systems. Many muscle cars came from the factory with 14- or 15-inch wheels but a typical aftermarket disc brake setup requires at least a 17-inch wheel to clear the caliper. In this case, the six-piston caliper is a fairly tight fit, even on an 18 x 10–inch wheel.
Even though six-piston calipers are all the rage in the Pro Touring world, most cars do not need that much braking power on all four corners. Most builders combine the six-piston caliper up front with a four-piston caliper out back for the perfect combination.