Maserati Ghibli 2016 Owner's Manual page 220

Driving
Department of Transportation
Uniform Tire Quality Grades
The following tire grading categories
were established by the National
Highway Traffic Safety Administration.
The specific grade rating assigned by
the tire's manufacturer in each
category is shown on the sidewall of
the tires on your vehicle.
All passenger car tires must conform to
Federal safety requirements in
addition to these grades.
Treadwear
The Treadwear grade is a comparative
rating, based on the wear rate of the
5
tire when tested under controlled
conditions on a specified government
test course. For example, a tire graded
150 would wear one and one-half
times as well on the government
course as a tire graded 100. The
relative performance of tires depends
upon the actual conditions of their
use, however, and may depart
significantly from the norm due to
variations in driving habits, service
practices, and differences in road
characteristics and climate.
Traction Grades
The Traction grades, from highest to
lowest, are AAA, A, B, and C. These
218
grades represent the tire's ability to
stop on wet pavement, as measured
under controlled conditions on
specified government test surfaces of
asphalt and concrete. A tire marked C
may have poor traction performance.
WARNING!
The traction grade assigned to this tire
is based on straight-ahead braking
traction tests, and does not include
acceleration, cornering, hydroplaning,
or peak traction characteristics.
Temperature Grades
The temperature grades are A (the
highest), B, and C, representing the
tire's resistance to the generation of
heat and its ability to dissipate heat,
when tested under controlled
conditions on a specified indoor
laboratory test wheel. Sustained high
temperature can cause the material of
the tire to degenerate and reduce tire
life, and excessive temperature can
lead to sudden tire failure. The grade
C corresponds to a level of
performance, which all passenger car
tires must meet under the Federal
Motor Vehicle Safety Standard No.
109. Grades B and A represent higher
levels of performance on the
laboratory test wheel, than the
minimum required by law.
WARNING!
The temperature grade for this tire is
established for a tire that is properly
inflated and not overloaded. Excessive
speed, under-inflation, or excessive
loading, either separately or in
combination, can cause heat buildup
and possible tire failure.
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" in this section)
may alert the driver about insufficient
tire pressure even though the driver is
responsible for regularly checking 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: