Tire overheating due to driving with low pressure, vehicle overloading, misalignment and a variety of similar conditions of abuse is well-known to contribute to tire failure. The cumulative damage which occurs on repeated overheating requires a reliable warning system. A simple indicator, which incorporates thermochromic materials into the sidewall as a non-structural rubber component, will show a persisting, vivid color change, reversible on cooling, when temperatures exceed a pre-determined set-point. The color is a clear reminder, when the vehicle is stopped, that a tire needs attention. The status of development, testing and related applications is reported.