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      10-02-2011, 07:55 PM   #48
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Drives: M4 Cab - Cayenne GTS - Jag XK
Join Date: Jul 2007
Location: Upper East Side Manhattan - Boca Raton FL - Lime Rock CT

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Originally Posted by View Post
Of course a certain amount of sidewall flex is needed - but the question is HOW MUCH? There is an optimum slip angle for max grip which depends on ALOT of things. The type of tires you're running (slicks, r-comps, streets have VERY different optimum slip angles). Also your alignment, weight, suspension, geometry will all matter. Just because you threw out a race car example doesn't make much of a point.

I have first-hand clinical results - running 18's versus 19's back to the back on the same car, same day with same alignment and same rubber I was able to shave off almost 4 seconds at road atlanta - thats what I have to report from experience from MY car - I don't speak for all.

The general rule of thumb is that for racing and high performance tires between 6 an 10 degrees of slip angle will generate maximum grip. If you are cornering and the slip angle is below its optimum range the tire is considered to be under-used. If it’s above this range the tire is being over-used. The trick is to stay within this optimum range so you use the tires to their fullest potential.

As you pointed out "Between 6 and 10 degrees" does leave some leeway as to what is the optimum amount and obviously there are other factors to be considered. My point is that the ideas that "the stiffer the sidewall the better the performance" and "the stiffer the suspension the better the handling" are only true to a point.

I do claim to speak for all either and I do not dispute your findings.

I will stand by my statement that "There is evidence that 18s will outperform 19s."


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Last edited by captainaudio; 10-02-2011 at 08:04 PM.