What is the difference between a fixed brake disc and a floating brake disc?
Floating brake discs are a major step forward in motorcycle braking system evolution. It became necessary to “free” the brake disc from its support because of the overheating to which it is exposed in hard braking, typical of racing use. The disc structure (low thickness to reduce weight and a large surface) is highly sensitive to thermal expansion: overheating will cause bad straining, in both the radial and the axial directions (i.e. parallel to the wheel axis), which, magnified by the fast rotation dynamics (bounce), will badly affect braking mechanics. The brake pads and pistons are therefore pushed back into the calliper, affecting braking efficiency. This problem can be solved by allowing some “setting” clearance for the disc, so that the disc is free to go out of shape, without negatively affecting braking. In practice, a number of cylindrical holders are interposed between the disc and its flange (which connects it to its wheel hub), allowing slight axial movement. Ducati uses
