Mitsubishi Evolution IX - Project Evo IX

The front rotors are 355mm, or 14 inches, in diameter and made from Brembo's proprietary cast-iron alloy. This alloy has a consistent coefficient of friction over a wide temperature range and is dimensionally stable of a wide temperature range as well. Brembo offers the rotors drilled or slotted. We opted for slotted because of the heavy expected track use. The slots offer an escape path for the vaporized pad material that is created under extreme use. Under really hard braking conditions this boundary layer of ablated material can actually act like a lubricant and the pad can hydroplane on the rotor surface. The grooves act like grooves on a tire and give the material somewhere to go so the pad's surface can have better bite on the rotors themselves. Brembo's GT rotors are also zinc chromate coated. This gold coating resists rust so you won't have rusty water dripping out of your brake vents and staining your expensive wheels every time you wash your car. The unrubbed areas of the rotor also won't get all rusty and crappy looking as time goes on. If your car is all detailed out, you might appreciate this feature.

The rotors are bolted in full-floating style to aluminum alloy hats. The alloy hats save a considerable amount of weight. Full floating refers to the fact that the rotors are attached to the hats with shouldered bushings that allow about 0.012 inch of free movement between the hat and the rotor. The advantages of floating the rotor are a reduction of stress on the rotor as it thermocycles. This makes the rotor much less susceptible to warping as the rotor is allowed to expand and contract without binding forces at the hat. The rotor wears more evenly over its service life if it is floated for these reasons as well. Floating rotors also keep the rotor at true centerline of the caliper, which reduces caliper piston knock back. Piston knock back is when the rotor warps or bearing play in the hub or flex in the spindle allows the rotor to knock the pistons back into the caliper when the brake isn't being engaged. Brake piston knock back is a serious issue in performance cars and can cause the brake pedal to be low and mushy unpredictably. Sticky race tires can also exaggerate the hub and spindle weaknesses and tend to make knockback worse.

A major drawback to floating rotor technology is that they cost more to produce. Tighter tolerances must be held in the machining of the rotor and hat. This means greater cost to the consumer. Another disadvantage is that floating rotors are typically noisy in use; the rotor tends to move around making a rattling noise when the car is driven. Those who are picky about odd noises in their car can be driven nuts due to this. Brembo has a unique, simply elegant solution to getting rid of most of this noise. They use a tension spring mounted to every other bolt to keep the rotor captured so it's still free to expand and contract but won't bang around and make much noise. This allows race floating rotor technology to be used on a kit for a fussy customer.

Even though the kit is huge, the rotor is much bigger and the caliper holds brake pads nearly twice the size as stock. The entire front brake assembly is 2 pounds lighter than the stock brakes, thanks largely to the elaborately machined monoblock calipers and alloy hats. Brembo warned us that the kit might not fit cars with 18-inch wheels. When we installed the kit, the calipers were very close to the inner rim of our CE28N wheels, there was only about 0.08-inch clearance, slightly under the 0.12 inch Brembo recommends.