What indicates that a tire tread is excessively worn?

The presence of tread wear indicators or bars is a clear and definitive sign that a tire tread is excessively worn. These indicators are built into the tire design and become visible when the tread depth reaches a specific minimum level, typically around 2/32 of an inch. When these indicators start to show, it signals to the driver that the tire is no longer safe for use, as insufficient tread depth can significantly impair traction, handling, and braking performance, especially in wet conditions.

While other options may provide some insights regarding tire condition, they do not serve as reliable indicators of tread wear. For instance, a change in tire color to gray may occur due to environmental factors or prolonged exposure to sunlight but does not necessarily correlate with the safety or tread depth of the tire. Increased air pressure in the tire does not indicate tread wear; rather, over-inflation can create uneven wear patterns and compromise performance. Noise while driving can be caused by various factors, including tire imbalance or misalignment, but it lacks the specificity of directly indicating tread wear issues. Only the visibility of tread wear indicators offers a consistent and objective measure of tread depth, making it the correct answer in determining whether a tire is excessively worn.