What is a "wear bar" found on tires indicative of?

A wear bar on tires is a specific feature designed to indicate the level of tread wear. When the tread of a tire wears down to the height of these bars, it signals that the tread depth has become dangerously low. This is essential because insufficient tread depth can significantly impair the tire's grip on the road, especially in wet conditions, and can lead to a higher risk of hydroplaning and loss of vehicle control.

Having wear bars helps drivers easily assess the condition of their tires without needing specialized tools. It serves as a visual cue that it's time to replace the tires for safety. In contrast, the other options refer to conditions or characteristics that do not directly relate to the function of a wear bar. For example, over-inflation affects tire pressure rather than tread depth, while proper tread depth would not be indicated by wear bars, as those signify that the tread is worn down. Excessive tire age is also related to the overall condition of the tire rather than specifically the tread depth measured by the wear bars.