Load Rating

A tire's load rating, sometimes signified by the load index code is the amount of weight that that tire is designed to carry within a maximum speed...




load rating visualThe maximum speed which the tire is designed to operate at it's speed rating and  the two are closely linked together --each affecting the other. (Read the linked article to learn how, if you're not certain.) 

Usually you even see the two indexes noted together when they're shown on the tire sidewall or written in technical descriptions of specific tires as in

225/50R16 89S

In the above example the three characters at the very end are what interest us.   The load rating of that tire is shown by the code 89 which, if you'll look in the table below is 1,279 pounds or 580 kilograms.  That is the maximum load, or weight which the tire is designed to be used with when operated at a speed no greater than the "S" speed rating indicates (112 mph).


If your needs are greater than wither of these indexes or ratings state, then you should be shopping for tires with ratings that at least meet what you expect to be using, otherwise you're inviting a problem to happen and, as most problems tend to do, likely at the most inconvenient time.

The load rating you need in a tire is calculated by adding up the total weight that will be carried on each axle and dividing by the number of wheels on that axle.  On a passenger vehicle such as a car or truck that's usually 2, but, as you've noted some vehicles will have 4 wheels across (and a very few specialty vehicles have only 1).

When you know the maximum weight that each tire on an axle is expected to carry you can then consult the table below to learn the load index you need.   In general terms, there is no harm in using a load rating which is greater because you are left with a larger margin of safety, but if you go far beyond what you normally expect to use on a regular basis, you may end up at least paying more for your tires than you need to since a greater load rating tends to be more costly than a tire with a lower rating.

Load Rating Table

Below are the load index ratings used for passenger cars and light trucks.  The range is from 71 to 110.  At lower levels you'll note that the Kg capacity increases 10 kg for each step up, but as levels rise, this increase is greater, reaching 30 in this table. The point is that there is no direct relationship between the index and the exact weight which the tire can carry -- you don't have to double the index to carry twice as much weight.

Load Index Pounds Kilograms
71 761 345
72 783 355
73 805 365
74 827 375
75 853 387
76 882 400
77 908 412
78 937 425
79 963 437
80 992 450
81 1019 462
82 1047 475
83 1074 487
84 1102 500
85 1135 515
86 1168 530
87 1201 545
88 1235 560
89 1279 580
90 1323 600
91 1356 615
92 1389 630
93 1433 650
94 1477 670
95 1521 690
96 1565 710
97 1609 730
98 1653 750
99 1709 775
100 1764 800
101 1819 825
102 1874 850
103 1929 875
104 1984 900
105 2039 925
106 2094 950
107 2149 975
108 2205 1000
109 2271 1030
110 2337 1060

Also see the article on speed rating.

Load Range

There is also a weight carrying rating system called Load Range which may be a bit confusing if you run into it and are not aware of how it is different from this system.  Read up on it in Load Range.



tireguy

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