What is the defect classification when a tire leak cannot be heard?

When a tire leak cannot be heard, it tends to fall into the minor defect classification. This classification indicates that while there may be a leakage, it is not significant enough to cause immediate safety concerns. Generally, minor defects are those that do not pose an immediate risk to the vehicle's operability or safety, and they often require attention but can typically be addressed at a later time without the need for urgent repair.

In the context of tire inspections, a leak that is subtle enough not to produce a discernible sound often suggests a slow air loss, which wouldn't compromise the structural integrity of the tire or the vehicle's performance right away. However, it is still important to monitor these kinds of defects regularly to prevent them from escalating to a more serious issue.

In contrast, major, severe, and critical classifications represent more serious defects that warrant immediate action due to potential safety risks. Major defects could indicate problems that affect the vehicle’s performance, while severe and critical issues could endanger the driver and other road users. Thus, classifying a tire leak that cannot be heard as minor aligns with the understanding that it requires monitoring and potential future action rather than immediate concern.