Porsche 928 ST1991 Owner's Manual page 87

Wheels
If you intend to use other than original equip-
ment wheels, be sure that they conform to
Porsche specifications for your model.
Check with your Porsche dealer regarding
the correct wheel specifications for type and
model year.
Removing and storing tires
The driving direction should be clearly
marked on all tires before removing them for
storage. This is to make sure that they are
mounted and run in the same direction as
before. When remounting, put tires with the
most tread depth at the front. Have tires/
wheels balanced as soon as possible.
The supposition that tires become long
wearing due to storage and age is un-
founded. Chemical additives, which make
the rubber elastic, loose their effectiveness
in the course of time and the rubber
perishes. Therefore, the tires, especially
the collapsible spare tire, should from
time to time undergo a visual check. For
this, pump up the collapsible spare tire.
Under no circumstances should tires be
older than 6 years.
The age of the tire can be seen from the
"DOT" code number. If, for example, the last
three numbers read 128, this means it was
produced in the 12th week of 1988.
Store tires in a cool and dry place.
86
Snow tires
For a better grip on snow and ice use radial
M+S tires or snow tires with studs. Check
with your local Motor Vehicle Bureau for pos-
sible restrictions.
WARNING
The standard tires profile and rubber mixture
are optimized for wet and dry driving condi-
tions, and may not prove favorable for snow
conditions. Therefore install M+S tires
before driving in such conditions. Failure to
use the proper tires and wheels could result
in loss of control and damage to the vehicle
and personal injury.
Before mounting snow tires, consult with
your Porsche dealer. He has the technical
information necessary to advise you on
wheel and tire compatibility.
Radial ply M+S tires should be inflated with
the same cold tire inflation pressures re-
quired for the regular radial ply tires. How-
ever, do not exceed the maximum tire infla-
tion pressure listed on the tire sidewall.
Snow tires should have the same load
capacity as original equipment tires and
should be mounted on all four wheels. Snow
tires with studs should be run at moderate
speeds when new in order to give the studs
time to settle.
When fitting tires already mounted on rims,
ensure that the colored wheel bolt is closest
to the valve. Always screw the lockable
wheel nut onto this bolt. When removing,
mark the direction of rotation on each wheel,
e.g. FR, FL, RR and RL This precaution en-
sures that the wheels will be remounted in
the same position, thus obviating the risk of
imbalance.
WARNING
Tires with badly worn treads and studs are
very dangerous. Make sure they are re-
placed immediately.
Do not drive a vehicle equipped with snow
tires at prolonged high speed. Snow tires do
not have the same degree of traction on dry,
wet or snowfree roads as a normal tire.
Furthermore, snow tires wear rapidly under
these conditions.
Snow tires do not fulfill their purpose if the
tread depth is less than 5/32 in/4 mm. Comply
with all state and local laws governing
snow tire and tread depth requirements.
Snow chains
Should snow chains be necessary, they
must be mounted on the drive wheels
only.
Check with local authorities for possible re-
strictions.
Use only snow chains with fine pitch links,
so that enough space remains between the
chains and the inside of the wheel arches.