A Guide to Tire Sizes and Ratings
It can be very confusing to know which tires you need to get if you don't understand the ratings system that is used. I mean, P275/75/R15 isn't exactly self-explanatory, is it?
The codes that are used to mark the various tire ratings are defined as listed below, which will help you to know which size and type you need regardless of the style or brand.
* Tire Type Most people understand that there are different kinds of tires for different kinds of cars. The letter P stands for a passenger tire and LT stands for a light truck.
* Tire Width It is important to have the proper tire width in order to ensure efficient handling, fuel efficiency traction and more. The ratings give the tire width in millimeters as a standard form of measurement, with approximately 25.4 millimeters making up one inch. The example given above would work out to be 10.8 inches in width.
* Aspect Ratio The term "aspect ratio" is used to measure the tire's height from the mount to the tread and is shown as a ratio that is compared to the width of the tire. The example above refers to a tire that has a height that is 75% of the tire's width.
* Construction Your tire's construction type is also very important, especially if you have specific needs. For example, the R stands for "radial" construction, which is a much more durable and strong type of reinforced construction.
* Rim Diameter In this case the diameter refers to the size of the wheel. It is very important that the tires you purchase have the exact same diameter of your vehicle's wheel. In the example above the 15 represents a tire that is 15 inches in diameter.
Now that you understand the basics behind the tire ratings, it is easy to understand that P275/75/R15 stands for a passenger tire that has a width of 275 millimeters, an aspect ratio of 75, boasts a strong, radial construction and is made to fit a wheel that is 15-inches in diameter.
* Information on Speed Ratings There are also speed ratings for today's tires, beginning at around 100 miles per hour on up. The speed rating doesn't really need to be a big concern for tires that will be used for average daily driving, as most vehicles rarely go above 70 or 75 mph. However, specialty cars such as sports vehicles, might need tires that are rated much higher than standard models.
The UTQG or Uniform Tire Quality Grading rating is another important measurement that you should know about, which can be found on the tire's inner sidewall. This rating is measured via a standardized testing system that rates the performance of the tire in relation to temperature resistance, traction and wear and tear on the tread. The NHTSA or U.S. National Highway Traffic Safety Administration sets these ratings, which are based upon these standards of requirements and control testings.
When you have an understanding of how tires are rated and measured, it will help you when you are looking at new tires for purchase with regard to the length that the tread should last under regular, daily driving; the temperature resistance in relation to build-up or heat dissipation; and traction, which is tested to compare durability in relation to braking on various surface types.
About the Author:
Bill McNeil is a former mechanic and self-proclaimed gear-head. To learn more about Mud Tires and ATV Mud Tires please visit our site.
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