Cadillac CTS Owner's Manual page 406

10-86 Vehicle Care
The Uniform Tire Quality
Grading (UTQG) system does
not apply to deep tread, winter
tires, compact spare tires, tires
with nominal rim diameters of
10 to 12 inches (25 to 30 cm),
or to some limited-production
tires.
While the tires available on
General Motors passenger cars
and light trucks may vary with
respect to these grades, they
must also conform to federal
safety requirements and
additional General Motors Tire
Performance Criteria (TPC)
standards.
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 tire when tested
under controlled conditions on
a specified government test
course. For example, a tire
graded 150 would wear one and
a half (1½) 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 – AA, A, B, C
The traction grades, from
highest to lowest, are AA, A,
B, and C. Those 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.