Maserati GranTurismo Owner's Manual page 49

Mark Meaning
Aspect ratio in percent (%)
30 - Ratio of section height to
section width of tire
Construction Code
• Z: means a tire usable at
speeds greater than 240
ZR
km/h (150 mph)
• R: means radial construc-
tion
21 Rim diameter in inches (in)
Load Index - A numerical
code associated with the
102 (*)
maximum load a tire can
carry
Speed Index - A letter indic-
ating the range of speeds at
which a tire can carry a load
corresponding to its load in-
dex under certain operating
conditions. The maximum
(Y) (*) speed corresponding to the
speed index should only be
achieved under specified
operating conditions (i.e.,
tire pressure, vehicle load-
ing, road conditions, and
posted speed limits)
(*) The load and speed index of the
tire may not appear on the sidewall
because they are not required by law.
NOTE:
Before choosing a type of tire, please
contact the Service Network who
will be able to indicate which tires are
suitable and compatible with the rims of
your car.
Tire Pressure
Proper tire inflation pressure is essential
for safety and best performance of your
vehicle. The tire pressure monitoring
system "TPMS" setup on the vehicle
(see "Tire Pressure Monitoring System
(TPMS)" in this section) may alert the
driver about insufficient tire pressure
even though the driver is responsible for
checking regularly the tire pressure.
Radial tires fitted on the vehicle may
look properly inflated even when they
actually are under inflated. Do not make
a visual judgment when determining
proper inflation.
Three primary driving aspects are
affected by improper tire pressure:
Understanding the Vehicle
Safety
WARNING!
• Improperly inflated tires are dangerous
and can cause collisions.
• Under-inflation increases tire flexing
and can result in tire overheating and
failure.
•
Over-inflation reduces a tire's ability
to cushion shock. Objects on the road
and potholes can cause damage that
result in tire failure.
• Over-inflated or under-inflated tires
can affect vehicle handling and can fail
suddenly, resulting in loss of vehicle
control.
• Unequal tire pressures can cause
steering problems. You could lose
control of your vehicle.
• Unequal tire pressures from one side
of the vehicle to the other can cause
the vehicle to drift to the right or left.
•
Always drive with each tire inflated to
the recommended cold tire inflation
pressure.
Economy
Improper inflation pressures may cause
uneven wear patterns to develop across
the tire tread. These abnormal wear
patterns will reduce tread life resulting
in a need for earlier tire replacement.
Under-inflation also increases tire
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