The co-cast brake disc also responds to the demand for much lighter components, in combination with an improved feel when braking in extreme operating conditions, and with increased resistance to fatigue at higher temperatures. As a result, incidences of both transient thermal deformation and permanent thermal distortion can be significantly reduced
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Transient deformation events occur typically when the brakes are applied, and the discs run hot, whereas permanent disc distortion is the main cause of vibration during braking in the vehicle.
Cast iron has optimum thermal properties — low deformability and good heat conductivity — as well as having process-related advantages, such as superior castability and machineability . It also has practical advantages, like good damping properties. Aluminium on the other hand is advantageously lightweight, being 2½ times less dense than cast iron, with the result that the co-cast disc can be made between 15% and 20% lighter than its integral counterpart, depending on the application.
This represents an important achievement, since car makers consider a 1 kg reduction in overall weight of the vehicle to be a real success, and even more so when “non-suspended” weight is removed, given the notably positive influence on comfort and driving precision.
Unlike an integral disc, the co-cast brake disc presents a symmetrical braking surface, favouring a more uniform temperature distribution when the brakes are applied: this means considerably less residual deformation after the brake is released (–70%). In addition, the co-cast concept allows that the brake ring it’s natural material properties and expand under heat. This effectively emulates the performance capabilities of a floating disc, but without the number of components needed for a floating assembly.
By virtue of the properties characterizing the two co-cast materials, this new disc succeeds in reducing wear both on the disc and on the pad in off brake condition.