off topic / traction control

[Chris Capowski]

> Are we talking strip or roadcourse use?  There's a difference in which
> direction you go, and I'd hope that everyone here can figure that one out.
>
> For what it's worth, my '96 Impala likes about 48 psi up front for
autocross
> use.  Even at that pressure, I can still get the first 1" or so of
sidewall
> to scrub if I'm really pushing it.
> Eric Bryant

I hate to beat a dead horse here, but there are two different issues here.
Increasing tire pressure to make up for poor suspension set up (not enough
camber/caster/toe) and tire pressure changes when the suspension is set up
properly.  If the suspension is not properly set up for cornering (which is
what I suspect for everyone using really high pressures (above 40#)) you
increase the pressure to reduce the amount of tire roll over.  In this case,
pretty much the higher the better, even though your contact patch is getting
smaller and smaller.  If the suspesnion is set up properly so that the
contact patch is level at full cornering g's, then generally the LOWER the
pressure the more traction you have, up until the contact patch gets really
distorted under load which causes excess heat and the tire overheats.  The
lower the pressure the larger the contact patch and the higher the pressure
the smaller the contact patch.

To give some data points of my own:

89 Civic Si tire pressure for best cornering g's:
street tires, stock suspension  42f/38r
street tires, adj camber, stiff suspension  28f/28r (factory recommended
pressures by the way)
race slicks, adj camber, really stiff suspension 18f/25r

Chris "Mighty Mouse" Capowski




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