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All about wheels and tires
Uniform Tire Quality Grading Stand-
ards
Overview of Tire Quality Grading
Standards
Uniform Tire Quality Grading Standards are
U.S. government specifications. Their purpose
is to provide drivers with uniform reliable infor-
mation on tire performance data. Tire manu-
facturers have to grade tires using three per-
formance factors: : tread wear grade, ;
traction grade and = temperature grade.
These regulations do not apply to Canada.
Nevertheless, all tires sold in North America
are provided with the corresponding quality
grading markings on the sidewall of the tire.
Quality grades can be found, where applicable,
on the tire sidewall between tread shoulder
and maximum section width.
Example:
R
Treadwear grade: 200
R
Traction grade: AA
R
Temperature grade: A
All passenger car tires must conform to the
statutory safety requirements in addition to
these grades.
i
The actual values for tires are vehicle-spe-
cific and may deviate from the values in the
illustration.
Treadwear
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 charac-
teristics and climate.
Traction
G
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.
!
Avoid wheelspin. This can lead to damage
to the drive train.
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 meas-
ured under controlled conditions on specified
government test surfaces of asphalt and con-
crete. 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 freezing
point.
Mercedes-Benz recommends a minimum tread
depth of ã in (4 mm) on all four winter tires.
Observe the legally required minimum tire
tread depth (Y page 305). Winter tires can
reduce the braking distance on snow-covered
surfaces in comparison with summer tires. The
braking distance is still much further than on
surfaces that are not icy or covered with snow.
Take appropriate care when driving.
Further information on winter tires (M+S tires)
(Y page 306).
Temperature
G
WARNING
The temperature grade for this tire is estab-
lished for a tire that is properly inflated and
not overloaded. Excessive speed, underinfla-
All about wheels and tires
319
Wheels and tires
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