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Old 04-03-2012, 04:07 PM   #36
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Join Date: Feb 2011
Location: Ottawa
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Originally Posted by dcramer View Post
Cut and paste, forgot the T

So is the difference between static and kinetic friction dramatically different for R-comp tires vs very good street tires ? Or stated another way do R-comps really break away faster than street tires ?
The way pneumatic tires generate grip is much more complicated than the Coulomb or "dry" friction model, which involves static and kinetic friction coefficients. Almost any decent modern vehicle dynamics book will have a chapter or more devoted to the subject. Look at offerings from Carroll Smith and Milliken for race car focused discussion. Milliken is the much more technical of the two.

Basically, the issue of "driveability" involves much more than rubber compound alone. Everything from the tire width, sidewall profile, carcass construction, wheel diameter, wheel width, and of course tire compound will affect driveability.

For learning to control a car at its limits, I would think a tire with a low cornering stiffness (makes grip at high slip angles) and one that makes near peak grip over a broad range of slip angles would be best. This points towards a relatively narrow tire with soft carcass/sidewall construction, on a relatively narrow wheel. I don't think this necessarily excludes r-compound rubber, rather that tires using r-compounds typically do not fit the rest of the description.

Alternatively, the approach taken in Karting (very high cornering stiffness and very narrow 'optimal' slip angle range) to learn how to control a car seems to have worked well for most F1 drivers.

Food for thought.

And back on topic: my advice would be to get a set of star specs, RS3's, XS's, or similar and spend the rest of your money on registration fees and consumables for track days.
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