Veteran technicians will remember the problems with composite rotors in the late 1990s. These rotors had hats of stamped steel cast into the iron rotor. They saved weight, but they were prone to runout and installation errors.
These types of rotors were on vehicles like the Chevrolet Malibu and Jeep Cherokee. Most OEMs abandoned this type of rotor design in the early 2000s.
In the past five years, we started to see a new type of rotor with aluminum cast hats. These are not rotors with a forged aluminum hat that’s mechanically attached to the rotor using fasteners; these rotors are two pieces that are cast together as one piece using new manufacturing methods. The two pieces float in a manner that allows the aluminum hat and cast iron rotor ring to expand at different rates without cracking. The resulting rotor is 15-20% lighter and is more heat resistant.
The bad news is that these rotors can’t be machined because of their floating design. Also, on the Cadillac CTS-V with the J56 brake package, the front rotors only allow for 2 mm of wear before they are below the discard measurement.
In addition to the Cadillac CTS-V, these rotors can be found on the Chevrolet Camaro ZL1 and Corvette. In Europe, Maserati and Mercedes Benz have vehicles in production. The future for this type of brake rotor is bright as fuel economy mandates increase.
