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

Uniform Tire Quality Grading Standards

328
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 =. These regu-
lations do not apply to Canada. Nevertheless,
all tires sold in North America are provided
with the corresponding quality grading mark-
ings on the sidewall of the tire.
All passenger car tires must conform to the
statutory safety requirements in addition to
these grades.
Where applicable, the tire grading informa-
tion can be found on the tire sidewall between
the tread shoulder and maximum tire width.
i
The actual values for tires are vehicle-
specific and may deviate from the values in
the illustration.
For example:
Treadwear
200
Treadwear
The treadwear grade is a comparative rating
based on the wear rate of the tire when tested

Traction

Temperature
AA A
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.
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.
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.
You should pay special attention to road con-
ditions when temperatures are around the
freezing point.
Mercedes-Benz recommends a minimum
tread depth of ã in (4 mm) for all four winter
tires ( page 316) to maintain normal driving
Y
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-
ered with ice or snow. Take appropriate care
when driving.
! Avoid wheelspin. This can lead to damage
to the drive train.