HOW TO READ A TIRE
Service Description (Letter P)
The service description may not always appear on the tire, but it is important to know how it can affect your vehicle. If there is a "P" on the sidewall, it stands for "passenger car." This refers to the U.S. (P-metric) method of tire sizing. "LT" stands for Light Truck, "ST" is for Special Trailer and "T" stands for Temporary, which is primarily used for small spare tires. If a tire does not have a "P" or another letter in front of the numbers, it is considered a "Euro-metric" tire. A Euro-metric tire conforms to the European tire specifications, and often carries a different load index than a comparably sized P-metric tire. We'll discuss load index in more detail below.
Tire Width (215)
The first number in this series refers to the tire's section width, or the distance from sidewall edge to sidewall edge, measured in millimeters up and over the tire's tread. Generally speaking, the larger this number is, the wider the tire will be.
Aspect Ratio (65)
This number is the tire's aspect ratio, or its section height compared to its section width. In this example, the section (or sidewall) height is 65 percent of the section width. This number can be indicative of a tire's purpose. Lower numbers, like 55 or less, mean a short sidewall for improved steering response and better overall handling.
Internal Construction (R)
The "R" refers to radial construction, which has been the industry standard in passenger-car tires for more than 25 years. Prior to radial tires, most cars came with bias-ply tires, which had a crude construction that made for poor handling. Bias-ply tires (which use a "B" for their description) are still used for certain truck applications.
Rim Diameter (15)
This is the wheel (or rim) diameter, in inches, for which the tire was sized. Pay particular attention to this number if you plan on upgrading your wheel size. If your wheel diameter changes, you'll have to purchase a new set of tires that matches this new diameter.
Load Index (95)
A tire's load index is a measurement of how much weight each tire is designed to support. The larger the number, the higher the load capacity. This is one of the most important numbers on your tire. To find out what "95" means, you have to look it up on a load carrying capacity per tire chart.
Ninety-five indicates a maximum weight of 1,521 pounds. Remember that this is per tire, which means you have to multiply by four to get the total capacity for a complete set of tires. If the vehicle has its original tires.
Speed Rating (H)
The speed rating of a tire is based on the Government standards for reaching and sustaining a specified speed. Typically, a tire with a higher speed rating results in better handling.
Speed ratings are determined via laboratory tests that simulate road performance at various speeds.Below is a list of speed ratings along with the corresponding speeds they represent. Remember that the speeds listed are test speeds and not recommended speeds. Speed ratings apply only to the tire itself, and not to a particular vehicle. Putting a tire rated for a certain speed on a vehicle does not mean that the vehicle can be safely operated at the tire's rated speed.
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