Does the heat paint return to its original colour?

The thermo graphic heat paint used in DBA 4000 and DBA 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;

Green         458˚C          (856˚F)        Changes to white 
Orange       550˚C          (1022˚F)      Changes to yellow
Red             630˚C          (1166˚F)      Changes to white

In order for this colour change to occur, the disc rotor mass must reach the relevant bulk temperature for 10 minutes. This ensures that the colour change does occur from the much higher surface temperatures which do not penetrate through the disc material and affect its mechanical properties.
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The ideal temperature condition for high performance brake pads and rotors is between 450˚C and 550˚C 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 specialised high temperature pad compound, review the car setup or alter your driving style. When exposed to temperatures in excess of 630˚C (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.