Which of these brake rotor thickness variations is the smallest that may require the rotor to be refinished or replaced during brake service?

The threshold for determining when a brake rotor may need to be refinished or replaced is generally based on the tolerance levels established for rotor wear and thickness inconsistency. A variation of 0.0006 inches is significantly smaller than typical dimensional tolerances that would influence brake performance.

In automotive applications, most manufacturers specify that any variation greater than approximately 0.002 inches might be a concern for rotor service. Since 0.0006 inches is less than this threshold, it indicates a very slight variation that is unlikely to affect the rotor's effectiveness or the overall braking system. This makes it understandable that such a minimal difference would not normally necessitate any action regarding refinishing or replacement.

This understanding contrasts with the other options, which represent much larger variations, and are indicative of conditions that would likely require further evaluation.