Wheels and tires, Uniform tire quality grading standards – Mercedes-Benz C-Coupe 2015 Owners Manual User Manual

Page 319

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.

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 Temperature
200

All passenger car tires must conform to the

statutory 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

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

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 305) to maintain normal driving

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-

Uniform Tire Quality Grading Standards

317

Wheels

and

tires