Reduced thickness reduces the heat dissipation capacity of the rotor and its mechanical strength, triggering a series of critical faults and failures, such as:
- the formation of thermal cracks on the braking surface, due to the rise in temperature and the reduction in the resistance thickness
- deformation of the brake rotor, resulting in vibrations and noise
- increased pedal travel, caused by reduction of thickness of the braking surface. In extreme cases, this can also lead to loss of tightness on the part of the caliper piston, with the risk of the pads themselves coming out of their seat or seizing.
In addition to the above problems, the use of a worn rotor could lead to the onset of another extremely dangerous phenomena, which could be generated in particular in conditions of heavy-duty vehicle use. These two issues are vapour lock and fading.
The high rotor temperature caused by a large number of braking actions - which is typical on a mountain trail - could generate the formation of vapour lock: in other words, the rise to above 200°C in the temperature of the braking fluid.
The fluid overheating generates air bubbles inside the circuit, air bubbles are compressible, which leads to no deceleration when pressing the brake pedal, despite being pressed all the way down.
The phenomenon of fading is also tied to the rise in temperatures, due to the reduction in the rotor thickness and the heavy-duty use of the vehicle. This rise in temperature reduces the friction coefficient between the brake pad and the brake rotor, with the ensuing increased braking distance.