by pdy on Tue Mar 14, 2006 8:35 am
Hi Ron:
I used to run these, but I don't have any AutoX pressure notes.
What I have done for years, and did when I was using the MX
on my SC is the following;
Mark the tire on the outer edge from about an inch on the tread,
to an inch on the sidewall using white shoe polish. Do this in two
or three places around the circumference of the tire, on all four.
Start with stock pressures, or maybe a couple pounds higher.
After the first lap or two, look at the marks on the tires to see
how far they have scuffed on the sidewall. You don't want it on
the sidewall, but you're looking for how far the tread is deforming
and the tire is rolling over. I found that it shouldn't go more than
about half-way over onto the sidewall - kinda like a 45° angle of
bevel. You want to run the lowest pressure that doesn't roll over
too far. Starting with a higher pressure allows you to easily let
some air out until it just is getting to that point.
Also, if you feel the car understeering (plow), you can add air to
the fronts, and if it's loose (oversteer) add it to the rears. Or, take
air out of the opposite end if it isn't close to rolling over too far.
You should see a correltaion between what you feel and the marks
on the tires. Like if it's understeering, you'll probably see that the
front tires are rolling over more onto their sidewalls than the rears.
Sorry, it's more wordy than just two numbers, but I hope this
makes some sense.
Best,
Paul.