A load index is an assigned numerical value that signifies a tire's maximum load carrying capacity. They're useful to help compare load carrying capacity of different-sized tires, and as you might expect, the higher the tire's load index number, the greater its load carrying capacity. Using the image below of a P195/60R15 87S tire, the load index is the 87 near the end. The 87 identifies the tire's ability to carry approximately 1,201 pounds.
Typically, the load indexes of the tires used on passenger cars and light trucks range from 70 to 126.
| Load Index | Pounds | Kilograms | Load Index | Pounds | Kilograms | Load Index | Pounds | Kilograms | ||
|---|---|---|---|---|---|---|---|---|---|---|
| 70 | 739 | 335 | 89 | 1,279 | 580 | 108 | 2,205 | 1,000 | ||
| 71 | 761 | 345 | 90 | 1,323 | 600 | 109 | 2,271 | 1,030 | ||
| 72 | 783 | 355 | 91 | 1,356 | 615 | 110 | 2,337 | 1,060 | ||
| 73 | 805 | 365 | 92 | 1,389 | 630 | 111 | 2,403 | 1,090 | ||
| 74 | 827 | 375 | 93 | 1,433 | 650 | 112 | 2,469 | 1,120 | ||
| 75 | 853 | 387 | 94 | 1,477 | 670 | 113 | 2,535 | 1,150 | ||
| 76 | 882 | 400 | 95 | 1,521 | 690 | 114 | 2,601 | 1,180 | ||
| 77 | 908 | 412 | 96 | 1,565 | 710 | 115 | 2,679 | 1,215 | ||
| 78 | 937 | 425 | 97 | 1,609 | 730 | 116 | 2,756 | 1,250 | ||
| 79 | 963 | 437 | 98 | 1,653 | 750 | 117 | 2,833 | 1,285 | ||
| 80 | 992 | 450 | 99 | 1,709 | 775 | 118 | 2,910 | 1,320 | ||
| 81 | 1,019 | 462 | 100 | 1,764 | 800 | 119 | 2,998 | 1,360 | ||
| 82 | 1,047 | 475 | 101 | 1,819 | 825 | 120 | 3,086 | 1,400 | ||
| 83 | 1,074 | 487 | 102 | 1,874 | 850 | 121 | 3,197 | 1,450 | ||
| 84 | 1,102 | 500 | 103 | 1,929 | 875 | 122 | 3,307 | 1,500 | ||
| 85 | 1,135 | 515 | 104 | 1,984 | 900 | 123 | 3,417 | 1,550 | ||
| 86 | 1,168 | 530 | 105 | 2,039 | 925 | 124 | 3,527 | 1,600 | ||
| 87 | 1,201 | 545 | 106 | 2,094 | 950 | 125 | 3,638 | 1,650 | ||
| 88 | 1,235 | 560 | 107 | 2,149 | 975 | 126 | 3,748 | 1,700 |
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.
Since LT tires are commonly used on trucks with dual rear wheels, they are branded with two load indexes. The first number indicates the load carrying capacity if the tire is installed on a truck with a single-wheel rear axle, and the second number applies when the tire is used in a dual rear application.
Though it may seem counterintuitive that a tire is rated to carry less weight when working in tandem with another tire in the dual pair, the purpose is to build in additional reserve capacity should one of the two tires fail, leaving the sole remaining tire to carry the load normally handled by two tires.
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