Which of the following measurements is NOT necessary for drum brakes?

Run-out is a measurement typically associated with ensuring that a rotor or drum is correctly aligned and does not have any warping or unevenness that could impact braking performance. While it is an important aspect in the context of disc brakes to ensure proper contact and function, it is not a critical measurement for drum brakes.

In the case of drum brakes, shoe thickness is vital to ensure that the brake shoes have not worn too thin to provide effective friction. The drum diameter is crucial as it directly affects the engagement of the brake shoes; if the diameter is out of specifications, it can lead to improper braking. Additionally, assessing the condition of the brake lining is necessary to ascertain whether the shoes will perform adequately. Thus, while each of these measurements supports the operational and safety standards required for drum brakes, run-out is the one that does not need to be measured routinely in this specific context.