Uniform Tire Quality Grading Standards; Traction - Mercedes-Benz 2015 GLK Operator's Manual

Uniform Tire Quality Grading Stand-
ards
Overview of Tire Quality Grading
Standards
Uniform Tire Quality Grading Standards are
U.S. government specifications. Their pur-
pose is to provide drivers with uniform relia-
ble information on tire performance data. tire
manufacturers have to grade tires using three
performance factors: tread wear :, tire trac-
tion ; and heat resistance =. All tires sold
in North America are provided with the cor-
responding quality class mark on the sidewall
of the tire, even though these regulations do
not apply to Canada.
i
The actual values for tires are vehicle-
specific and may deviate from the values in
the illustration.
Where applicable, the tire grading informa-
tion can be found on the tire sidewall between
the tread shoulder and maximum tire width.
For example:
Treadwear

Traction

200 AA
All passenger car tires must conform to the
statutory safety requirements in addition to
these grades.

Uniform Tire Quality Grading Standards

The treadwear grade is a comparative rating
based on the wear rate of the tire when tested
under controlled conditions on a specified
U.S. government 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, how-
ever, and may depart significantly from the
norm, due to variations in driving habits, ser-
vice practices and differences in road char-
acteristics and climate conditions.
The traction grades, from highest to lowest,
are AA, A, B, and C. Those grades represent
the tire's ability to stop on a wet surface as
measured under controlled conditions on
specified government test surfaces of asphalt
and concrete. A tire marked C may have poor
traction performance.
The safe speed on a wet, snow covered or icy
road is always lower than on dry road surfa-
ces.
Temperature You should pay special attention to road con-
ditions when temperatures are around the
A
freezing point.
Mercedes-Benz recommends a minimum
tread depth of ã in (4 mm) for all four winter
tires (
characteristics in winter. Winter tires can
reduce the braking distance on snow-covered
surfaces in comparison with summer tires.
Stopping distance, however, is still consider-
ably greater than when the road is not cov-
Treadwear
Traction
G WARNING
The traction grade assigned to this tire is
based on straight-ahead braking traction
tests, and does not include acceleration, cor-
nering, hydroplaning, or peak traction char-
acteristics.
page 335) to maintain normal driving
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