Where should the dial indicator be placed when preparing to measure radial runout on a wheel tire assembly?

To accurately measure radial runout on a wheel tire assembly, the dial indicator should be placed on the rim bead seat perpendicular to the axle. This positioning allows for the most precise measurement of any deviations in the circular geometry of the wheel as it rotates. By placing the dial indicator in this orientation, you can effectively gauge how much the tire and wheel assembly is out of round.

When positioned perpendicularly, the dial indicator can register fluctuations in the radial plane—which is crucial for identifying any issues that could lead to uneven tire wear or vibrations during driving. If the indicator were placed parallel to the axle or on the tire itself, it could introduce inaccuracies in the measurement, as those positions may not detect the full extent of the deviations relevant to the tire's and wheel's axes of rotation. This thorough understanding of positional adjustment is essential for achieving reliable runout measurements.