Thread: understeer
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Old 06-17-2009, 01:10 PM   #9
stephen wilson
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Join Date: Apr 2008
Location: Southern New jersey
Posts: 1,054
To add to what renzop stated, changing the tire pressure does two things:

1) Changes the tire spring rate, in which case they behave as blue200s mentioned , lower pressure= lower spring rate and more grip at that end.

2) Changes the tire profile & stiffness. Too low, the tires roll over and overheat the shoulders of the tire. Too high and they crown too much, reducing the contact patch and overheating the center of the tread. Some cars need high front pressures to prevent the tires from rolling over (probably not a Boxster problem)

The best way to maximize total grip would be to fit the widest tires possible, and use an adjustable sway bar or spring rates to adjust the balance. Of course your alignment and tire pressures have to be optimized. The only reason you would ever go with narrower tires would be that the rules require it, such as with spec Boxsters.

Oh yeah, as he also mentioned,driver technique can also induce under/oversteer

Steve
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