From geelongvic, about halfway down. https://www.curbsideclassic.com/vintage ... just-fine/First let’s discuss tire wall rigidity and tire break-away. In the early days of radial tires ( Michelin X) the sidewalls were very flexible allowing significant side wall deflection of several inches until the tread would final abrupt lift footprint reduction resulting in abrupt terminal understeer in front engined cars and abrupt terminal oversteer in rear engined cars. The high performance Michelin XWX tires series addressed this issue with significantly increased sidewall rigidity making this the ideal tire for high performance cars like the Ferrari 275 GTB in the 1960’s.
Later Michelin developed its TRX ( see Paul Niedermeyer’s article on the TRX in the CC blog) line of “performance” tires in the late 1970s and 1980, with significantly increased sidewall flexibility/ reduced sidewall rigidity unfortunately increasing sudden footprint breakaway characteristics combined with less than optimal tread patterns and less than optimal compound “stickiness”. The sidewall flexibility breakaway characteristics of the TRX tires ( up to 2-3 inches sidewall deflection during cornering) fundamentally contributed to the poor reputation
All of which is why TRX's have such a bad reputation here.