Porsche 928 GT1991, Owner'S Manual

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Drive wheels must rotate freely with chains
mounted to prevent damage to body, axle
or brake components. Follow instructions
issued by the supplier of the chains. Remove
chains as soon as roads are free of ice and
snow.
Tire designations
Due to new speed and load ratings for radial
tires, new designations have come into force
for snow tires for your Porsche.
The designation to be used for ZR tires is
e. g., 245/45 ZR 16 (Z = code letter for radial
tires for speeds above 240 km/h (149 mph).
Tire Pressure Warning System
The tire pressures are monitored by a warn-
ing system that
• monitors correct tire pressure more pre-
cisely and reliably than any tire-pressure
gauge in the tool kit, at a service center
or workshop,
• takes the effect of temperature on tire
pressure into account. (Style of driving,
load, roadspeed, outside temperature,
sunlight and the heat radiated by the en-
gine affect the temperature of the air in
the tires),
• assures excellent handling and low fuel
consumption by correct tire pressures,
• helps prevent incipient tire damage and
increased tread wear due to low tire pres-
sures.
Method of operation
Two pressure-operated switches in each
wheel monitor the tire pressures. If the pres-
sure in the tire drops beneath the trip pres-
sure to which the switches are set (front 2.35
bar, rear 2.85 bar) or if there is a malfunction
in the system, a corresponding message ap-
pears in the display in the instrument cluster.
When the ignition is switched on, the warn-
ing light in the instrument cluster comes on
as a check. The light goes out as soon as the
engine is started. Automatic tire-pressure
monitoring begins once a distance of ap-
prox. 20 meters (66 ft) has been covered at
a speed of at least 5 km/h (3 mph).
The tire pressure warning system takes the
effect of tire temperature on tire pressure
into account. Nevertheless, it is possible that
the pressure in the tire may not be as high
as the pressure required for a given driving
situation.
Therefore, the system may not issue a warn-
ing immediately after the car pulls away.
Even if the tire pressure is not corrected, the
warning may not be repeated after the igni-
tion has been switched off and the car re-
started, if the same conditions do not re-
occur. Nevertheless, the pressure is too low
for a particular combination of speed and
temperature, in other words, for a particular
driving situation.
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