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Speed Rating and Load Index Charts of Tires

Speed Rating and Load Index Charts of Tires

The numbers and letters engraved on a tire reflect, among other things, its load bearing and speed handling capacity. These are important specifications provided by the manufacturer, and are a part of that tire's rating.
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All tires have alpha-numeric characters engraved on their inner sides. These engravings are specific codes, which provide the user with information on the dimensions of the tire and its key limitations, such as load-bearing ability, the maximum speed it can achieve, temperature and traction.
Starting from 1991, all manufacturers have been marking the service descriptions on the tires. The following section explains what speed rating and load index imply, and also provides tables representing the typical values of both these ratings found on most tires.
Tire Rating Charts: Speed Rating and Load Index

Load Index
The load index is an assigned numerical value, that identifies the tire's ability to carry load. The higher the tire's load index, the greater will be its capacity to carry load. The load indexes of the tires used on passenger cars and light trucks, typically range from 70 to 110.
Load Index Pounds Load Index Pounds
71 761 91 1356
72 783 92 1389
73 805 93 1433
74 827 94 1477
75 852 95 1521
76 882 96 1565
77 908 97 1609
78 937 98 1653
79 963 99 1709
80 992 100 1764
81 1019 101 1819
82 1047 102 1874
83 1074 103 1929
84 1102 104 1984
85 1135 105 2039
86 1168 106 2094
87 1201 107 2149
88 1235 108 2205
89 1279 109 2271
90 1323 110 2337

Speed Rating
The speed rating is indicative of the tire's capacity to move at high speeds. Most of the ratings are based on laboratory tests, where the tire is pressed and rotated against a large diameter metal drum to simulate load and determine its speed. Do note however, that no matter how high the speed rating of a tire is, one shouldn't exceed the legal speed limits.
The code for speed rating, is made up of one or two letters, or one letter and one number, and indicates the maximum permitted speed that the tire can sustain, without being damaged.
Code mph km/h Code mph km/h
A1 3 5 L 75 120
A2 6 10 M 81 130
A3 9 15 N 87 140
A4 12 20 P 94 150
A5 16 25 Q 100 160
A6 19 30 R 106 170
A7 22 35 S 112 180
A8 25 40 T 118 190
B 31 50 U 124 200
C 37 60 H 130 210
D 40 65 V 149 240
E 43 70 Z over 149 over 240
F 50 80 W 168 270
G 56 90 (W) over 168 over 270
J 62 100 Y 186 300
K 68 110 (Y) over 186 over 300

Most tires use the ISO Metric sizing system for their specifications. The European Tyre and Rim Technical Organization (ETRTO) and the U.S. Tire and Rim Association (T&RA) are the two major standardizing organizations for rating speed and load indexes of tires.