When measuring the parallelism of a disc brake rotor, a technician finds a 0.002" variation. What is the next step?

In the context of assessing a disc brake rotor's performance, the next step after identifying a 0.002" variation in parallelism is to determine the rotor's minimum "machine to" thickness. This step is crucial because it helps establish if the rotor can be machined to bring it into acceptable parallelism without compromising its structural integrity.

Rotors have a specified minimum thickness below which they should not be machined or used, as reducing their thickness too much can lead to overheating, warping, and overall reduced braking performance. By determining the minimum thickness, the technician can ascertain whether machining the rotor is feasible, or if it has already reached the point where replacement is necessary. This assessment is vital for ensuring safety and optimal braking function by preventing potential issues that can arise from using a rotor that is too thin or worn out.

While re-measuring the disc for accuracy, inspecting brake pads for wear, or even replacing the rotor may seem like reasonable steps, they do not address the critical need to understand whether the rotor is still viable for resurfacing. Without confirming the minimum thickness, any further actions might lead to inappropriate decisions regarding rotor reconditioning or replacement.