Load Range, Ply - Speed Rating & Load Index

Tire Article

Load Range Issues with the Hummer

It seems that more often than not getting the tires that you want is becoming a crap shoot. Last year I was looking for Toyo's and you couldn't get any. This year you can get the Toyo's but Goodyear is backordered.

This whole issue came up when Goodyear GSA's were on national backorder (10/2007) and I was looking for an alternate highway tire for the Hummer. In a conversation with Tom Cepek he suggested that I consider the Yokohama Geolandar A/TS 37/12.50R-17 Load Range "D". which has a less aggressive tread than the GSA and would be a very good 'on road' tire. I was concerned that it was a load range 'D' and not 'E'.

The Yokohama and the Goodyear GSA both have a load capacity of 3525 @ 50 psi per tire. Since 50 PSI is the maximum amount of pressure you can put in the tire using the CTIS pump, for all practical purposes the tires are equal in the load they will carry. The differance is if you pumped the GSA up to 65 psi it could carry 4080 lbs. Over many years of using GSA's I have found that the correct pressure for good tire wear is 35 psi on a lightly loaded wagon.

Add to that and regardless of the load range, both tires only have a two ply carcass.

Having said all that, if you are using your truck lightly loaded and not pulling a giant trailer there doesn't seem to be any difference using certain 'D' rated tires. Ultimately, the decision is up to you.

Load Range and Ply Rating

Info for this page taken from Tirerack.com and DiscountTire.com

Ply ratings and load ranges identify load and inflation limits of a given tire size when used in a specific type of service.

• Ply ratings: An older method of rating load capacity.
• Load ratings: The current method of rating a tire's load-carrying capacity.

	Load Range	Ply Rating	Load Pressure
LT-metric	B	4	35 psi
LT-numeric	C	6	50
Flotation LT*	D E F	8 10 12	65 80 95

Speed Ratings:

L = off road
P = 93 mph
Q = 99 mph

Load index

The load index refers to the load-carrying capacity of a tire, or how much weight a tire can support. For example, if a tire has a load index of 89, it can support 1,279 pounds (from below chart) at maximum air pressure. Multiply that by four (4 x 1,279 = 5,116 pounds) to get your maximum load-carrying capacity. It is not recommended to install tires with a lower load index than what came on your car from the factory.

Load   Index Load (lbs)   Load Index Load (lbs)   Load Index Load (lbs)   0 99 50 419 100 1764   1 102 51 430 101 1819   2 105 52 441 102 1874   3 107 53 454 103 1929   4 110 54 467 104 1984   5 114 55 481 105 2039   6 117 56 494 106 2094   7 120 57 507 107 2149   8 123 58 520 108 2205   9 128 59 536 109 2271   10 132 60 551 110 2337   11 136 61 567 111 2403   12 139 62 584 112 2469   13 143 63 600 113 2535   14 148 64 617 114 2601   15 152 65 639 115 2679   16 157 66 639 116 2756   17 161 67 677 117 2833   18 165 68 694 118 2910   19 171 69 716 119 2998   20 176 70 739 120 3086   21 182 71 761 121 3197   22 187 72 783 122 3307   23 193 73 805 123 3417   24 198 74 827 124 3527   25 204 75 852 125 3638   26 209 76 882 126 3748   27 215 77 908 127 3858   28 220 78 937 128 3968   29 227 79 963 129 4079   30 234 80 992 130 4189   31 240 81 1019 131 4289   32 247 82 1047 132 4409   33 254 83 1074 133 4541   34 260 84 1102 134 4674   35 267 85 1135 135 4806   36 276 86 1168 136 4938   37 282 87 1201 137 5071   38 291 88 1235 138 5203   39 300 89 1279 139 5357   40 309 90 1323 140 5512   41 320 91 1356 141 5677   42 331 92 1389 142 5842   43 342 93 1433 143 6008   44 353 94 1477 144 6173   45 364 95 1521 145 6393   46 375 96 1565 146 6614   47 386 97 1609 147 6779   48 397 98 1653 148 6844   49 408 99 1709 149 7165         150 7385