The Load Index and Speed Rating
The load index and speed Rating refer to the maximum load capacity and speed the tire is rated for. The load index is the first set of numbers and the speed rating is the alphabetical letter that follows.
Also called the Service Index or Service Description, the chart below details what the load index and speed rating stands for.
Width or Section Width
The width is measure from sidewall to sidewall in mm
Aspect Ratio or Series
The Aspect Ratio is the ratio of the section height to the section width. The number is calculated by: (Section Height/Section Width) X 100
The diameter of the rim in inches
UTQG stands for Uniform Tire Quality Grading and is a standardized rating system designed by the United States government. It measures the expected tread life of a tire, gripping power and traction, and maximum temperature ranges.
This number is a relative grading system where the rating 200 means that the tread is expected to last twice as long as a tire rated 100. The rating is given based on testing taken on a government approved track.
The traction rating measures the braking power while moving straight on pavement. The ratings start from C and go up from B to A to AA.
The temperature rating is a measurement of the tire’s heat dissipation rate. The ratings start at C and go up to A
Tires marked with the M+S symbol mean that the tire meets the Rubber Manufacturers Association standards for mud and snow use. Therefore the tires are all-weather with a self-cleaning tread and superior traction in muddy or light snowy conditions.
The alpine marking signifies that the tire meets or exceeds the Rubber Manufacturers Association standards for heavy snow weather use. These tires are often for winter only use.
The arrow of the rotation symbol signifies the rotational direction of the tire on uni-directional and asymmetric tires.