When checking the wear on ball joints with a dial indicator, what must be ensured for accurate readings?

For accurate readings when checking the wear on ball joints using a dial indicator, it is crucial to ensure the correct wheel bearing adjustment. This is because improperly adjusted wheel bearings can lead to excessive play or movement in the wheel assembly, which would significantly affect the dial indicator readings. Any free play in the wheel bearings can mask the actual wear present in the ball joints, leading to misleading results.

In contrast, while proper tire pressure, vehicle alignment, and brake pad condition are all relevant factors to overall vehicle performance and safety, they do not directly influence the accuracy of the dial indicator measurements during a ball joint inspection. Hence, the primary factor to consider for reliable readings in this specific assessment is the adjustment of the wheel bearings.