When purchasing vehicle tires, it is very important to make sure that they are appropriately suited to the vehicle. In particular, tires with the correct load rating much be purchased so that vehicle safety is not compromised.
The load rating is a measure of the tire's strength--its ability to hold air pressure under load.
The load rating influences the sidewall strength of a vehicle tire. If a tire has a load rating that is too low, the handling of the vehicle could become unstable as the sidewall buckles under the vehicle's weight. Conversely, a much higher load rating than needed can dramatically harshen ride quality.
The recommended load rating for a vehicle's tires can be found in its owner's manual. It is also normally affixed to a sticker located on one of the vehicle's door jams. If you are replacing tires supplied with the vehicle from the manufacturer, the load rating written on the tires is an appropriate guide.
Tires have different load ratings depending on the inflation pressure of the tire. For example, a tire may have a higher load rating when inflated to 38psi than when inflated to 32psi. Always ensure that the desired load rating can be obtained at the vehicle manufacturer's suggested tire inflation pressure.
Car tires have the load rating expressed in numbers. Truck and light-duty tires have the load rating expressed as a letter of the alphabet in ascending order. Therefore, a tire with a "D" load rating would be able to withstand significantly more weight at a given air pressure than an "A" rated tire.
The load index is a number that corresponds to the physical load-handling weight of a tire in kilograms or pounds. The load index can be used as a cross reference to find the weight in pounds or kilos. For example, a load index of 105 corresponds to 2,039 pounds or 925 kilograms. This chart is found inside the vehicle's door jams and is available in tire replacement shops.
