The Tire Load Index and Speed Rating are part of the tire size.
Lets take, for example, tire size 225/50 R17 98H (as pictured above). The 98H at the end represents the service description. The service description is composed of the load index and the speed rating. The load index would be 98 and the speed rating would be H for our example. Below you will see what each means and understand them. Since 1991, service descriptions have been required on all tires.
The load index is a numerical value assigned to each wheel to identify the load carrying capabilities. The higher the load index, the greater it’s load carrying capabilities are. Using 98 as our example load index, once again, our tire has a maximum load capacity of 1,653 pounds.
The speed rating is a letter assigned to the wheel to identify the maximum speed at which the tire is rated as running safely. Using H as our example speed rating, our tire has a maximum speed of 130 miles per hour. Although the tire is rated as being capable of safely reaching this speed, it is highly advised you to adhere to the speed limits.
These ratings only apply tires with no prior damage and those that are properly inflated. The actual speed rating and load index may change based on the tire’s tread, road conditions, driving habits, and weather.