When does a front tire fail an inspection?

A front tire will fail an inspection if the tread on two adjacent grooves anywhere on the tire is less than 3mm. This criterion is crucial because tread depth significantly affects a tire's ability to grip the road and perform safely, particularly in wet or slippery conditions. A minimum tread depth ensures adequate contact with the road surface, which is essential for traction, handling, and effective braking. Tires with insufficient tread depth can lead to longer stopping distances and an increased risk of hydroplaning.

The other options relate to important considerations for tire maintenance and safety but do not directly correlate to failing an inspection as clearly as tread depth does. For instance, while proper inflation is essential for tire efficiency and safety, the specific PSI requirement may vary depending on the vehicle and tire specifications, and not all tires have a blanket minimum such as "less than 30 PSI." Visible cracks in the sidewall are indeed a concern, indicating possible tire degradation, but they may not alone trigger a failure, depending on the severity and depth of the cracks. Similarly, while age can affect tire performance, simply being over 5 years does not automatically mean a tire has failed inspection; factors such as wear, usage, and environmental exposure also play critical roles.