The "official " NASCAR definition, attributed to various drivers,
including Richard Petty, is" oversteer is when the rear end hits the
wall first, understeer is when the front end hits the wall first.
It is my belief that lower pressure (to a point) allows more tire
contact surface in a lateral direction, during cornering, therefore,
more grip. Higher pressure results in a firmer sidewall, less rollover &
"give", & less lateral traction. In hard cornering, the contact patch
changes size & shape from what it was in a straight line situation.
Whether you are braking or accelerating also affects what happens going
through a corner, as weight shifts to the rear during acceleration, to
the front during braking. I have seen some E production racers with
higher front tire pressures on a particular road course because they
could brake before entering the corners & accelerate through them. It
all seems to be a "black art" to me.
Perhaps Barney & others can give a better explanation
Jim Stuart
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