Being a Rookie on Street Tires, Hints & Tips [draft 1]
an Introduction for the San Francisco Region Rookie Classes
by Darren Madams - November 22, 1997
Permission to reproduce in any form as long as credit is retained.
[hint, hint -- in a rookie welcome pack]

Preface:
As of January 1st, 1998, the San Francisco region requires all participants
in the rookie classes to compete on Street Tires defined as having a DOT
treadwear rating of at least 120.  This guide will aid you in selecting
pressures & driving autocrosses with reduced traction tires.  The author
campaigned a 1990 Integra from November 1996 until October 1997 in the
Rookie CSP class on cheap Yokohama street tires with a treadwear rating of
320.  While not competetive with the front-runners of the class
(all of whom were running race tires), he did manage to finish first of
competetors on street tires fairly often.

Tires:
The goal of the new rule is to allow Rookies a place to "run what they
brung" without the pressures & expense of buying and competing with people
on autocross-specific tires such as BFGoodrich's R1 or Hoosier's Auto-X
radial.  We hope that this will lead to more rookies continuing with Solo2
and purchasing dedicated autocross tires and competing in the open classes.

While it is acceptable by the rules to purchase near-race tires such as the
Yokohama Nexus or Toyo Proxies T1 just to dominate a class, this practice
would be considered very poor sportsmanship.  You can learn just as much on
all-season tires from Sears because winning is not always the most
important thing.  If you are going to proceed in Solo2, you will definately
want to purchase dedicated tires.

Tire wear will eventually become a problem as the outside shoulders of
flexible-sidewalled tires will eventually disintegrate and reduce the life
of your tires.  Tire warranties, especially extended warranties offered by
stores, will often not cover you for this time of wear.  It is my
recommendation to avoid tire warranties at all costs.  Also, due to the odd
inflation (usually higher) and excessive camber & allignment settings,
tires will often not wear as evenly as during regular street use.  Frequest
tire rotation is highly recommended.

If you are trying to decide on new tires for the Rookie class, it is
recommended to choose tires that fit your daily driving best.  Remember,
autocrosses are held only once or twice a month and the average amount of
actual driving time is usually less than 5 minutes.  It is not worth
compromising your commute time by purchasing stiff-sidewalled or
excessively soft compound tires.  Certain tires will be better suited for
autocrossing, usually they are softer compund with less tread depth and
stiffer sidewalls.  Examples are Pirelli's PZero, <insert here> and other
tires that fit in the Ultra High Performance category.  The cost of wearing
out a set of these tires is usually more than a dedicated autocross tire.

Allignment Settings:
I can only speak for the Integra (and possibly other heavy front drivers)
as far as allignment goes but there are plenty of books in this area.  You
probably want as much negative camber as possible (up to about 2.5^o) with
a little extra in front.  You may want a little additional toe-out front &
rear to help reduce understeer and help increase turn-in capabilities.

For a rear-driven car, you'll have to ask one of the Corvette or C Prepared
dudes if they'll be nice enough to share with you.  I hear large quantities
of budweiser help. :)

You will notice that there is a certain allignment specification from the
factory.  The Miata, for example, comes with more negative camber in the
rear.  You might want to use this as a guidline.

Starting Pressures:
Generally, Solo2 requires higher tire pressures than is usually required
for street driving.  Most tire manufacturers recommend 34-36 psi all
around.  You may have already modified these pressures to balance your car
on the street.  Printed on the sidewall, there should be a maximum inflation
recommendation.  It is fairly safe to ignore this by a few psi during your
runs but it is advisable to set the tires back to normal street pressures
at the conclusion of the event.

General theory states that you should inflate the FRONT tires roughly 6-8
psi above normal.  Pressures of around 42 should be a good start.  You
should then adjust the REAR to neutralize the handling.  Usually for a
heavily understeering car, you may need a little less than street
pressures.  For rear-driven or heavily oversteering cars, you might want a
little more than street pressure. <double check me pls>

How to adjust Pressures:
It is essential to note that while it is possible to refine a car with
minute changes in tire pressures, it is not the best way to make a car
handle properly.  Tire manufacturers designed a tire for maximum grip at a
certain pressure, any deviation from that pressure is a sacrafice in one
area or another.  Other ways to adjust the handling of a car include
springs, shocks, sway-bars, weight distribution, allignment and driving
style.  You should purchase a very accurate tire guage and make sure to use
the same guage each time so as to keep consistent readings.  You will want
to purchase of borrow an air tank or air compressor to increase pressures
on grid.  Keep a log book of tire pressures and how they felt and what times
you ran.  You may find that although it feels better, you may not be going
as fast.  You may want to eventually purchase a tire pyrometer to
accurately record tire temperatures but that will come later.

Before diving too deep into adjustment theory, it will help to first
understand how a tire gets grip.  Tires are made of rubber that works its
way into the tiny grooves and pits of the road surface.  It creates a
friction which makes it difficult for a force to move against it.  It is
important to note that it is the rubber that actually creates the friction
and not the tread or tread blocks themselves.  In fact, tread blocks cause
a tire to flex even more (imagine pushing the eraser end of a new pencil on
a table) which causes instabilty & unwanted weight transfer.  These reasons
are why race tires (especially "slicks") do not have deep tread.

Although fairly obvious, the "contact patch" of the tire is often
misunderstood.  While a tire may have a 205mm width and a certain
circumfrance, only a small portion of that is actually in contact with the
road at a certain point, usually about 60-70%.  Since a tire is actually
convex (out like a sphere), only the center portion is in full contact.  As
you work your way to the outside of a tire, it will lift up a little.
Increasing pressure makes the tire more convex with decreases the contact
patch which decreases absolute traction.

However, the advantage of the increased pressure is that the tire will
"roll over" less which will actually result in better (probably not more)
traction.... up to a point.  Too low a pressure will result in sloppy tires
and too much friction on the outside edge of the tire. It is fairly
difficult to find the ideal point.  This is where shoe polish and attentive
driving come into play.  Every run should be well documented and well used
for the purpose of training.  If you did not learn something and make an
adjustment after a run, you will never improve.

To mark tires, make a fairly heavy mark accross the sidewall of your tires
in 3 spots with standard liquid shoe polish (I use Kiwi brand).  Don't make
the mark too thick as it will not rub off easily enough, but don't make it
so thin that you can not easily identify it.  Take your run and examine the
mark.  You will be able to see where the tire rolled over to by where the
polish has been scrubbed off.  If it is down the sidewall too far (where
you can tell the different type of rubber), you should add a little more
air.  Depending on current pressure and the surface and the course and the
amount of runs, add at least 1psi or more at a time.  Try not to adjust too
much at once but do not be afraid to make drastic changes if you can not
obviously feel the difference.  If you can not understand the mark or do
not know the direction to adjust, ask your fellow competetors; most will
gladly steer you in the right direction if they will not give you the
answer directly.

When driving, you should also be aware of feelings such as "snappiness", 
"drift", "break-away", "flex" and numerous others.  I put these in quotes
because there is no exact definition on any consistency to the description 
of these states.  With experience, you should be able to feel is a car is
not turning in sharp or quickly enough -- this is a sign of underinflation.  
If a car feels slick or like it's on ice then you are most likely
overinflated.  Try to think what the tire is doing and how it is reacting
to certain types of corners (quick slaloms or slow sustained sweepers) and
how your steering input is affecting the grip.  Sometimes a model (such as
the pencil and eraser example) will help to clarify this.

You will also want to listen to the squeeling of the tires.  With time and
experience, you will notice the tone will change with air pressure,
temperature or limits of the tire.  The combination of all these elements
will slowly help you narrow down the ideal pressures to start at.  Make
sure to start there again at the next event but refine it for your
increased driving skill and the style of course.

You may want to also note the temperature of the tire accross the tread.
If your car has adjustable allignment mechanisms, and it is legal for your
class, you may be able to increase handling and traction by correctly
reading tire temperatures.  In theory and in an ideal world, you would most
likely want tire temperatures to be even across the surface.  This would
mean that no part of the tire is working harder than another (remember heat
is caused by the friction).  However, this theory isn't exactly true
because often times you can sacrafice odd temperatures to give you a larger
advantage on one section of the course or during braking or...  You can
quickly and unscientifically feel any major problems by quickly running
your hand across the tread while the tires are still hot (careful!).  With
a pyrometer, you should record 3 specific points and always use the same
points.  Remember this is only for general use as driving and course
differences can result in wild variations of tire temperatures.

Since the pressure will increase as the tires heat up, you should start
with fairly high pressures but expect them to jump up quickly.  On your 3rd
or 4th run when the tires should be hot already, you will notice less of a
drastic difference.  Make sure to reset the pressures after each run.

Driving with Street Tires:
Since an autocross course will be tighter and more convoluted than most
roads, a normal street tire will be hard-pressed to keep up with the
required traction.  It is very important to understand the limits of your
tires and find ways to use their maximum traction for longer without
pushing it past the limit and losing time.

Smoothness is key!  Even though your street tires are very forgiving, you
will find that making minimum steering inputs in a smooth controlled manner
will result in faster times.  This does not mean be slow to move the wheel
of ease on the brakes, it just means that you shouldn't "surprise" the
tires.  Quick inputs will upset the balance of the car and the harmony of
the tires.

You should understand fully the friction circle and the theoretical maximum
possible traction of a tire.  In the friction circle, you have 1 unit of
traction.  You can use all of this for forward motion and none for lateral,
all lateral and no forward (not possible really), or some combination of
both.  The circle points out that if you are trying to accelerate, you are
left with less possible traction to turn.  You must balance the proportion
between the two -- if you are making a tight turn, don't try to accelerate
at full power.  Conversly, if you are in a gentle sweeper, you can probably
use a lot of throttle without overpowering the tires.

The most common rookie mistake is carrying too much speed through a corner.
On street tires, the traction required to complete this task is way more
than the tire can possibly give.  This results in the tire giving away
(sometimes dramatically) and not giving you any traction at all.  My
biggest recommendation for rookies is to slow down before corners by
hitting the brakes hard (but gently), making the turn and getting back on
the power sooner.

A trick that is hard to discover and even harder to bring yourself to do is
what is sometimes called "shimmying the wheel".  What this involves is
during a turn where you are running out of lateral traction while trying to
accelerate and the tires are breaking away, you simply (hmm...) turn the
wheel back the other direction a little bit and then feed it back the other
way into the turn again.  Do this rapidly a couple of times so that the
tire regains grip before it is progressively asked to push its limits
again.  It is similar but different to rapidly shaking the wheel. This is
totally counter-intuative and hard to do in practice but will result in a
huge decrease in time.  Practice makes perfect.

Sometimes there is nothing you can do and you will just have to slow down
to the speed the tires want to do.  Don't worry if this is the case -- your
competetors will be having the same problem.  By admitting there's nothing
you can do and not forcing the tires, you will actually be a step ahead of
them as they will be exceding the limits of the tires which will scrub off
speed or put them off course.

Make sure if you do hit a cone to continue on and forget about the past.
It helps to turn your mirror around so you won't look back.  Make sure you
get back on your line and continue at the same place.  At this point, you
have probably lost the time battle but your should still make it a learning
run for the tires.  Don't push extra hard as that will destroy your
temperature and tire marks readings as well as getting you frustrated.

Keep a close ye on the competition.  Make sure to watch their runs
(especially if they are in a similar car) and watch their mistakes and
their successes.  Instead of getting just the usual 3 or 4 runs, you are
effectively getting much more (to a degree).  Note how they are adjusting
their tires & suspension.

In Conclusion:
I don't know how to conclude this, I've said everything I want to say.  Just
go out to the next event and enjoy!