What is not a focus during a visual inspection of the tires?

During a visual inspection of tires, it is crucial to focus on aspects that can easily be observed without specialized equipment. Checking for sidewall damage, inspecting tread depth, and assessing for proper inflation are all directly observable conditions that can influence the safety and performance of the vehicle.

Measuring the tire's grip on the road, however, cannot be accurately done through a simple visual inspection. Grip is a performance characteristic that depends on various factors, including tire material, tread pattern, and road conditions. While tread depth is indicative of potential grip, a visual inspection alone cannot quantify how well a tire will perform when in contact with the road surface. Therefore, it is not a focus during the visual inspection process, making it the correct choice in this context.