Does the heat paint return to its original colour?
The thermo graphic heat paint used in DBA CLUBSPEC 4000 and 5000 series disc rotors has been developed to measure the actual bulk temperature of the disc when operating at the most extreme condition. This peak condition is reached when the vehicle is in full motion with the brakes engaged. To enable an accurate measurement to be recorded, it is essential that the heat monitoring paint makes a permanent change at this critical point in braking.
If the paint were to return to its original colour as it cooled you would not achieve a true indication of the peak temperature as the disc can reduce in temperature by more than one hundred degrees Celsius before you have time to stop and check the reading.
The three paint stripes on these DBA performance rotors are;
In order for this colour change to occur, the disc rotor mass must reach the relevant bulk temperature for 10 seconds. This ensures that the colour change doesn’t occur from the much higher surface temperatures which do not penetrate through the disc material and affect its mechanical properties. The ideal temperature condition for high performance brake pads and rotors is between 458 oC and 550 0C which is when the peak friction condition is achieved. This can be verified when the Green paint changes to white and the Orange paint has not changed or minimal change occurs on the outer edges.
If your driving conditions force the Orange paint to change to yellow then you should consider more a specialized high temperature pad compound, review the car setup or alter your driving style. When exposed to temperatures in excess of 630 oC (Red paint) permanent fatigue and stress concentration is greatly accelerated which may result in premature cracking or warping of the disc rotor. DBA does not warrant disc rotors that have been subjected to motor sport use.
Bulk Temperature is the temperature achieved through the full thickness of the material rather than surface temperatures that may be much higher but have less effect on the mechanical properties of the rotor material.
Disc Brakes Australia