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Understanding Your Tire

Tires are an integral component in the engineering and design of any car, truck, or SUV. The suspension, steering, braking, and many other system elements are all connected to the tires that carry your vehicle safely down the road. Use this section to read and understand the markings on the sidewall of your tire.

  • Department Of Transportation (DOT) Tire Identification Number

    The presence of this number means the tire meets or exceeds U.S. Department of Transportation’s safety standards. This ID consists of a series of numbers and letters indicating both where and when the tire was created. The first two numbers or letters are a plant code that tells you where the tire was manufactured. The last four numbers tell you which week and year they were made in.

    • This number can be easily located on your sidewall by the presence of the letters "DOT".

    • The four digit number lets you know the week and year a tire was made. For example, a tire manufactured in the 17th week of 2006 would be marked 1706.

  • Load Index

    This number tells you how much weight each tire is designed to support at its designated speed level when properly inflated. It’s usually paired with the speed rating that can be found on your tire sidewall directly after the size information.

  • Maximum Load Rating

    The maximum load rating can also be found on the tire sidewall. It states in both kilograms and pounds the maximum amount of weight each tire can handle. If you have four identical tires, you can determine the maximum supported load your vehicle can handle by multiplying that number times four. If you have two sets of tires with different load ratings, then multiply each number by two and add them together to get your total.

  • Maximum vs. Recommended PSI

    Maximum PSI tells you the highest amount of air pressure a tire is built to handle. This number is printed directly on the sidewall of any tire. Recommended PSI, on the other hand, is the amount of pressure the vehicle manufacturer recommends. This number can be found in your owner’s manual or on the tire information placard located on the driver side door jamb or in the glove box. Always inflate to the recommended PSI.

  • Size

    There are three important tire measurements to remember when selecting a tire: section width (measured in millimeters), the aspect ratio (expressed as a percentage), and the rim diameter (measured in inches). These three numbers determine which tires are compatible with your vehicle. The tire size is simply an expression of these numbers placed together. For example, a P255/50R16 tire would be a P-Metric passenger tire with a section width of 255mm, a 50% aspect ratio, which is sometimes called the series, having Radial construction and a 16" rim, or wheel diameter.

    • Section width: This tells you the distance from sidewall to sidewall when fully inflated and bearing no load.

    • Aspect ratio: This is the ratio between the height and width of a tire; aspect ratios of 70 or lower have a shorter sidewall for improved steering response and handling while higher aspect ratios ensure a smooth, comfortable ride.

    • Rim diameter: Tells you the diameter of the rim in inches.

    While some vehicles require that you have the same size and ratings on all four tires, others may have different standards for the front and rear; consult your owner’s manual or a Sears Auto Center associate for more details.

  • Speed Rating

    The speed rating tells you how fast your tire was designed to be driven for long distances. This rating is expressed as a letter that designates a category.

    Q 99 mph H 130 mph
    R 106 mph V 149 mph
    S 112 mph W 168 mph*
    T 118 mph Y 186 mph*
    U 124 mph    
  • UTQG

    UTQG stands for the Uniform Tire Quality Grading System. This rating system was established by the Federal government in order to provide a more consistent basis for comparing certain characteristics of car tires, primarily treadwear, traction and temperature tolerance. Truck tires and winter tires are not required to have a UTQG rating. The grades are not given by the Federal Government, but are determined by the tire manufacturer based on the manufacturer’s independent testing.

    Each characteristic has its own grading system. Tread wear is measured in terms of how it performs in relation to a control tire. A tire with a tread wear rating of 100 meets the same tread wear as seen in the control tire - meaning that 100 is the baseline for tread wear ratings. For example, if a tire has a rating of 350, it should take 3.5 times longer to wear down than one with a rating of 100. So basically, the higher the tread wear rating, the longer the tire should last.

    Traction measures how well a tire is able to come to a stop on wet pavement test track only. No traction on dry pavement or cornering is tested. Grades, from highest to lowest are AA, A, B, and C.

    Temperature resistance determines how well a tire can dissipate heat at different speeds. This is important because extended periods of heat build up can break down and shorten the life of the tire. Temperature ratings are stated as A, which is the highest, B, or C. The higher the rating, the more speed a tire can handle at higher temperatures.

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Having the right winter tires on your vehicle can increase control, fuel efficiency, and overall traction. They’ re constructed from different compounds and with tread that’ s specially designed for ice, snow, and sleet. Since they’ re more geared for colder climates than all-season tires, you should consider the following before making your choice.