46 What is the proper tire inflation for my car for performance driving?
Description
This article is from the VW Performance FAQ, by with numerous contributions by Jan Vandenbrande others.
46 What is the proper tire inflation for my car for performance driving?
A:For performance driving things are a bit differently from
normal inflation pressures because there the aim is to
reduce tire flex and to adjust the over all handling
characteristics of the car. Generally, in an autocross or
a ralley you will be running at a much higher pressure
than normal. One of the old tests is to put chalk marks
on the side of the tires, go around the track, and check
how much the tire has "rolled" under (i.e., how much flex
caused you to scuff the sides of the tires).Note -- this
only works on "street" tires. The sidewalls on
competition tires are just too stiff for the chalk
technique to work -- you need to use a pyrometer and a
stopwatch.
where@maple.circa.ufl.edu on chalk:
Typically speaking, If you run street tires when you
autoX, you'll want to bump the pressures up from what you
run on the street, but ONLY for the time you're racing.
When your racing day is done, bleed the pressures back
down to reasonable street pressures, and drive home.
Many of the autoXers I've talked with run "race tires"
while they race. They bring them in the trunk and take
them home in the trunk, and only run them around the
track. WHY? because these guys run racing slicks, and
everyone knows that racing slicks will KILL you if you
run them on the street and it decides to rain. If that is
not enough, you can be written a citation by the police
for running "bald
tires" if you are caught running slicks on the road...
Ok, now if you're still not sure how much pressure to run
in your street tires, ask someone who has a nice
(professional looking) AutoX car out at the track.
There's some sort of formula relating to a set of chalk
marks that you make on your tires. You "chalk the tires,
make a run, and analyze the chalk marks". If you find
someone who has raced several times, they'll usually be
nice enough to explain it to you, and help you out.
Contrary to what some may think, If you are just starting
out autoXing, the veterans are actually VERY willing to
help you out and explain things like tire pressures and
driving techniques. Most of them would talk your head off
if you wanted to listen that long, they're a really
friendly bunch from what i've found. The rationale for
explaining things to novices is to shorten the time that
it takes to get the car tweaked, so that you can spend
more time behind the wheel perfecting your driving
technique. Afterall, it's driving technique that really
makes the difference, They'll tell you that. :)
fisk@cvdv99.mayo.edu (Tom Fisk | 751 Siebens | 6-4261):
OK...there are several ways to determine proper tire
pressures for autocross. The scientific way says that you
run a few circuits and then check your tire temperatures.
The temperatures should be even from the outside, middle,
and inside of the tires. If the tire is warmer in the
middle, then your tires are OVER-inflated. Warmer on the
edges means that they are UNDER-inflated. If you get
variation from one side to the other, than that means you
could adjust your camber (+ camber if the inside is
warmer than the outside) and visa-versa.
For novice drivers in FWD cars on street tires, I would
recommend starting at 40-45psi in the front and 30 in the
rear. With experience, this will change. Novices need a
little more up front than experienced drivers, because
they always turn the wheel too far and never unwind
properly on the way out of a corner.
Continue to:
My Books
