Load Range, Ply - Speed Rating & Load Index
Updated December 2, 2014
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
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|
L = off road
P = 93 mph
Q = 99 mph
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.