Using a P195/60R15 87S tire size as our example, the 87S at the end of the size represents the tire's service description. A service description identifies the tire's load index and speed rating. Service descriptions are required on all speed rated (except for Z-speed rated) tires manufactured since 1991.
The first two digits (87S) represent the tire's load index and are followed by a single letter (87S) identifying the tire's speed rating.
"Using a P195/60R15 87S tire size as our example, the 87S at the end of the size represents the tire's service description. A service description identifies the tire's load index and speed rating."
P195/60R15 87S - The load index (87) is the tire size's assigned numerical value used to compare relative load carrying capabilities. In the case of our example the 87 identifies the tires ability to carry approximately 1, 201 pounds.
The higher the tire's load index number, the greater its load carrying capacity.
89 = 1, 279 pounds
88 = 1, 235 pounds
87 = 1, 201 pounds
86 = 1, 168 pounds
85 = 1, 135 pounds
A tire with a higher load index than that of the Original Equipment tire indicates an increase in load capacity. A tire with a load index equal to that of the Original Equipment tire indicates an equivalent load capacity. A tire with a lower load index than the Original Equipment tire indicates the tire does not equal the load capacity of the original.
Typically, the load indexes of the tires used on passenger cars and light trucks range from 70 to 110.
When looking at light truck (LT) or newer Special Trailer Service (ST) tires, there are two load indexes branded on the sidewall, separated by a forward slash. Using an LT235/75R15 104/101S Load Range C tire as an example, the load index is 104/101. 104 corresponds to 1, 984 pounds, and 101 corresponds to 1, 819 pounds. So what is the true load carrying capacity of the tire? The answer changes depending on the situation in which the tire is being used.