Color coordination is key in building a true performance car. Scratch that. Forget I said anything (even though I really meant it). That the color of Brembo's calipers match Project Miata's inimitable hue is purely an auspicious coincidence. I didn't choose to utilize the 313mm two-piece floating rotors and Brembo's renowned red four-piston Gran Turismo calipers because they'd look good nestled behind the 17-inch RO_JAs. Oh, no. The real reason these brakes were chosen is because they are huge, offering, among other things, impeccable heat dissipation, an issue that surprisingly plagues the lightweight roadster.
Taking a gander at the factory brakes reveals why the Miata can be manufactured at such little cost. The brake design, like many imports, is, for the lack of a better word, simplistic. The front rotors are vented and measure 10 inches in diameter and the calipers are a sliding, single-piston design. At best, these stoppers are adequate for average street driving, but once you push the car to its limits you'll quickly learn the limitations of such a setup.
Even though the stock brakes have only single pistons, sliding calipers seem like they would still push the brake pads onto the rotors with equal force across the face of the pad. They don't. The problem is the leading edge of the pad tends to bite hard into the spinning rotor, digging that end in and pulling the trailing edge out. The result is not only uneven pad wear, but also less brake pad contact patch on the rotor, which leads to longer braking distances, excessive pad heat, and premature pad wear. The solution to this problem is to run a multiple-piston caliper offering sequentially sized pistons.
The Gran Turismo package utilizes Brembo's aluminum (i.e., lightweight) GT2 caliper, which houses four pistons: two inboard and two outboard. The two pistons on the leading edge of the caliper are 36mm in diameter, while the trailing edge pistons measure a stouter 40mm. The sequential piston design allows more force to be placed at the rear of the brake pad, which subsequently presses the brake pad against the rotor evenly, offering even pad wear and a greater contact patch.
Brembo's Gran Turismo kit also includes 313x28mm, two-piece, cross-drilled, vented, floating rotors. What makes the Brembo rotor so great is the entire unit is built to handle and dissipate the intense heat that is generated during harsh driving. One of the ways this is accomplished is through the use of a cast-iron rotor bolted to a billet aluminum hat with fasteners that utilize springs on every other bolt. If you run your fingers over the bolts, every other bolt connecting the hat to the rotor should mildly move. These are known as McLaren clips. This design preloads the assembly and offers the benefits of a floating design while eliminating annoying disc noise.
Once the brakes were installed on Project Miata, a simple process that took roughly an hour and a half, the brakes were bled. The process of bleeding brakes is a simple one, but if done wrong it could mean the end of your life. The GT2 caliper only has one bleed screw, which is located at the top of the caliper, whereas some of Brembo's larger calipers utilize inboard and outboard bleed screws. Once the brakes are bled per Brembo's directions, Brembo recommends completing a second bleeding. The second bleeding should take place after the car has been driven at least a mile or two. Driving the car will usually knock any trapped air bubbles to the top of the caliper, meaning if you don't bleed the brakes a second time, you will be driving with air in the line, and that, my friends, is a bad thing.