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Here is a good, low-tech, article about tires from the recent Chicago Section PCA newsletter:
THE OWNERSHIP EXPERIENCE
from Loeber Porsche and Jack McCall
Pavement - The Surface To
Which Tires Should Stick
Unlike tracks that usually provide a
consistent surface; roads, especially
back-roads, have a tendency to
change surfaces. Warning signs will
not alert you as to when this may
occur. The changes will occur
abruptly and sometimes often.
This can be unnerving to the driver
who has just settled into a groove.
While the driver is providing the
proper amount of lateral acceleration
to plant his Porsche based upon the
amount of adhesion provided by the
current surface, the road suddenly
takes on all new characteristics. The
quickly changing parameters play
havoc with the safety margins.
There must be room for adjustment,
or it’s adios my friend.
Again, the worst case scenario
should be your guide. Rain may
cause hydroplaning, but a light mist
can be far more dangerous. If the
weather has been dry for a while,
the light mist will pull the oils out
of the pavement making the surface
as slippery as ice. A heavy rain
will actually wash the surface.
Hydroplaning is easily recognizable
in a Porsche. Slowing down will
solve the problem. The mist must
be dealt with the same way. Slow
down based upon intuition; the
abrupt warning provided by
hydroplaning just won’t happen.
Another scenario to consider is
that evaporation doesn’t occur as
quickly in the shade. As you go
in and out of sun light the surface
can change.
A couple of years ago I found myself
on AR 23, the “Pig trail”, and ran
into a light mist. Knowing that I
was about to give up traction, I
surrendered my pace. My assault
on this beautiful stretch of road
was spoiled, but both I and my
Porsche would survive to return
and avenge the loss. Sometimes
discretion is the better part of valor.
Remember, “Slick happens”.
Leaves, especially wet leaves, gravel,
oil, water, and different surfaces can
all contribute to the loss of traction.
You cannot wait until it happens and
then attempt to correct the situation.
It is essential to anticipate and make
concessions for inconsistencies that
can interrupt your forward progress
in a most despicable manner. Make
it a rule to expect the unexpected.
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