What is NOT a valid reason for rejecting tires?

The key aspect of tire rejection criteria focuses on safety and performance. A difference in brand does not automatically constitute a reason for tire rejection. Tires from different manufacturers can still meet the same safety standards and performance specifications, provided they have comparable tread depth, pressure, and type. What matters more is that the tires on a vehicle are uniform in size and load rating for optimal handling and safety.

In contrast, the other reasons listed are valid for rejecting tires. A difference in age can affect the tire's rubber composition and overall integrity, potentially leading to failure. A difference in tread design may alter handling characteristics and performance in various conditions, which can pose a safety risk. The presence of cracks is a clear indication of potential structural failure, which is critical for safe operation. Thus, the correct rationale for rejection centers around tire safety and performance, rather than brand diversity.