Your tire's load rating tells you the maximum weight capacity that your tire is designed to handle. The higher the tire-load rating, the more weight your tire can handle. However, do note that the tire load rating number itself is not the actual weight limit. For example, a tire-load rating of 105 means that these tires can handle a maximum-weigh capacity of up to 2,039 pounds (925 kilograms). In addition, your tire also has a different marker on it that tells you the load rating at a given inflation pressure.
The tire's load rating is considered part of the markings on your tire that make up its service description. The second piece of information that makes up your tire's service description is its speed rating. The speed rating is represented by a letter and tells you the maximum speed at which this tire can go, assuming the car isn't carrying a load that exceeds the tire's load rating. Since the speed rating is a letter (for example, a speed rating of "S" means that the tire can handle a maximum speed of up to 112 miles per hour/180 kilometers per hour), you'll have to check out a chart to learn what speed each of letters indicates. Why they decided to encrypt these ratings instead of just printing the actual number is anyone's guess.
There are a number of other markings on your tire, including the uniform tire-quality grading (UTQG) system ratings from the U.S. National Highway Traffic Safety Administration; these ratings tell you the tread wear, traction and temperature capabilities of your tires. Some manufacturers' information (such as tire type, width, aspect ratio, construction type, and rim diameter) is also included.
Originally Published: Jul 27, 2011