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SF Bay 50F temps and tire hardness...


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I've noticed that during the current cool mornings (50F and lower) my 996 tires (Pirelli Rossos) start very hard and only become supple after warming up (which requires running at 80MPH or higher). Have the local SF Bay Porsche owners experienced the same?

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My Bridgestone S03's do the same. I think it is the soft compound rubber used in performance tires.
Loren: You mean... "soft compound" needs to warm up to be functionally soft and sticky.

This is quite interesting. This means that in cold climates (even without snow/ice) one will be forced to install winter tires, which may be naturally softer at low temps, I guess.

Edited by Loren
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This is a material property of rubber and other polymers. Essentially, a given rubber compound has a temperature (known as glass transition temperature, or "Tg") where a transition in the stiffness/modulus occurs. The change can be rather significant and can occur over a rather small temperature range, meaning the stiffness is one thing at 40 degF and altogether something different (i.e. stiffer) at 30 degF. Chemical/engineering trade-offs of Tg usually involve the wet/dry/snow traction parameters and are linked or correlated to hysteresis and other tire/rubber performance metrics.

--Brian

Edited by Q-Ship986
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