A dial indicator is used to measure ___________

A dial indicator is a precise measuring tool that is commonly used to assess small distances or variations in parts. When it comes to brake systems, one of its primary applications is to measure runout, which refers to the deviation from the desired shape of a rotating part.

In the context of the question, selecting rotor runout as the correct answer highlights that a dial indicator can effectively measure the slight wobble or misalignment of the rotor as it spins. This is crucial because excessive runout can lead to uneven braking, vibrations, and premature wear of brake components.

When measuring rotor runout, the dial indicator is positioned against the surface of the rotor, and as the rotor is rotated, any variations in its surface level will cause the dial gauge needle to move. This movement indicates the extent of runout present.

While brake drum pulsation and brake drum runout are also related concepts, they specifically pertain to brake drums and may not be the best fit in relation to rotor measurement. Similarly, rotor thickness variation might be assessed through other tools or methods instead of a dial indicator which focuses more on deviations in the flatness or alignment rather than thickness.

Consequently, recognizing that the purpose of a dial indicator in this context is to evaluate