When measuring maximum thickness variation of a disc brake rotor, the technician should use a/an

• A. Disc Brake Micrometer
• B. Dial Indicator
• C. Micrometer Caliper
• D. Vernier Caliper

Answer: (A)

Measuring maximum thickness variation around a brake rotor requires a tool that can provide precise thickness readings on the rotor face at multiple points around its circumference. A disc brake micrometer is designed for this exact task. It lets you measure the rotor’s thickness at several circumferential positions with controlled contact pressure, giving you accurate numbers for each spot.

By taking readings around the rotor and comparing the largest and smallest values, you determine the maximum thickness variation. This is essential because excessive variation can cause uneven pad contact and pulsing.

A dial indicator is great for checking runout, which is a different kind of measurement about the rotor’s alignment as it spins. A standard micrometer caliper or a vernier caliper isn’t ideal here because they’re not as practical for reaching the rotor’s surface around its circumference or providing the consistent, precise measurements needed for MTV.

So the disc brake micrometer is the best tool for this purpose.