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Uniform Tire Quality Grading Standards

Mercedes-Benz GL-Class / Mercedes-Benz GL-Class Owners Manual / Wheels and tires / All about wheels and tires / Uniform Tire Quality Grading Standards

Overview of Tire Quality Grading Standards

Uniform Tire Quality Grading Standards are


Uniform Tire Quality Grading Standards are U.S. government specifications. Their purpose is to provide drivers with uniform reliable information on tire performance data.

Tire manufacturers have to grade tires using three performance factors: 1 tread wear grade, 2 traction grade and 3 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.

Where applicable, the tire grading information can be found on the tire sidewall between the tread shoulder and maximum tire width.

Example:
Х Treadwear grade: 200 Х Traction grade: AA Х Temperature grade: A All passenger car tires must conform to the statutory safety requirements in addition to these grades.

The actual values for tires are vehiclespecific 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 test track 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 conditions.

Traction

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 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 surfaces.

You should pay special attention to road conditions 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  . 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)  .

Temperature

WARNING

The temperature grade for this tire is established for a tire that is properly inflated and not overloaded. Excessive speed, underinflation, or excessive loading, either separately or in combination, can cause excessive heat build-up and possible tire failure.

The temperature grades are A (the highest), B, and C. These represent the tire's resistance to the generation of heat and its ability to dissipate heat when tested under controlled conditions on a specified indoor laboratory test wheel. Sustained high temperature can cause the material of the tire to degenerate and reduce tire life, and excessive temperature can lead to sudden tire failure. The grade C corresponds to a level of performance which all passenger car tires must meet under the Federal Motor Vehicle Safety Standard No. 109. Grades B and A represent higher levels of performance on the laboratory test wheel than the minimum required by law.

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