When checking for parallelism on a disc brake rotor, the technician can use a

When checking for parallelism on a disc brake rotor, the technician can use a

• A. Dial Indicator
• B. Caliper gauge
• C. Micrometer
• D. Feeler gauge

Answer: (C)

To check if a disc brake rotor is parallel to its mounting plane, you need a tool that can reveal small angular deviations as the rotor turns. A dial indicator fits this job perfectly because you mount it on a stand and let its contact point touch the rotor surface. As you rotate the rotor, any movement shown on the dial indicates runout, which directly reflects how parallel the rotor faces are to the mounting surface. The goal is minimal runout, meaning the rotor sits true and parallel. A micrometer, while excellent for precise single-point thickness measurements, doesn’t reveal how the rotor surface runs relative to the mounting plane or across the entire face as it rotates. It measures a distance at one spot, not the consistent parallelism around the whole diameter. Caliper gauges and feeler gauges have uses, but they don’t provide the direct, rotationally sensitive measurement of runout that a dial indicator offers.

To check if a disc brake rotor is parallel to its mounting plane, you need a tool that can reveal small angular deviations as the rotor turns. A dial indicator fits this job perfectly because you mount it on a stand and let its contact point touch the rotor surface. As you rotate the rotor, any movement shown on the dial indicates runout, which directly reflects how parallel the rotor faces are to the mounting surface. The goal is minimal runout, meaning the rotor sits true and parallel.

A micrometer, while excellent for precise single-point thickness measurements, doesn’t reveal how the rotor surface runs relative to the mounting plane or across the entire face as it rotates. It measures a distance at one spot, not the consistent parallelism around the whole diameter. Caliper gauges and feeler gauges have uses, but they don’t provide the direct, rotationally sensitive measurement of runout that a dial indicator offers.