Quote:
Originally Posted by oil pan 4
"if stretching really was a performance improvement why is it that no does it in F1, Grand Am, Le Mans, etc"?
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It is and it isn't. There is a point where stretch helps, and a point where you've gone too far. The reason behind you not seeing it in those race series is all about the rules. The wheel width may be mandated, but the tire not. Or both may be a "spec".
The hot setup for many small autox cars is a 225 stretched on a 9" wheel. This is what we ran on the STR Miata I was co-driving last year. The tires generate less heat and flex less (and this resulted in us having to run some silly low pressures at some rain events - like 20psi front, 18 rear) Note that it looks nowhere near as stretched as the red car shown earlier, but it is a stretched tire.
GRM did a test recently with 255s vs 245s of the same tire on the same 9" wheel and the 245s were faster.
I'm a total hater of the "Stance" crowd tire and camber choices, but to lump it all together and assume that everyone is rubbing and that all stretch is risky and offers no benefits is simply unfair.