The Michelin TRX is a high-performance tire introduced in 1975, notable for its unique metric sizing system that integrates the tire and wheel design for improved handling and comfort. Unlike conventional tires, which have separate bead and rim measurements, the TRX's design allows for a lower, more even sidewall flex, enhancing grip and stability. It was widely used on high-performance European cars in the 1980s, including the Ferrari Testarossa, BMW M635CSi, and Renault Alpine. Due to its specialized design, TRX tires require specific TRX wheels and are not compatible with standard rims. Today, Michelin still produces TRX tires for classic car enthusiasts, ensuring period-correct performance and aesthetics.