Tire Education

The load range or ply rating branded on a tire's sidewall helps identify its strength and ability to contain air pressure. While specific load ranges are assigned to passenger tires, load ranges are identified in ascending alphabetical order for light truck tires (the further along the letter is in the alphabet, the stronger the tire and the greater amount of air pressure it can withstand and load it can carry). Before load ranges were adopted, ply ratings were used to identify the relative strength of light truck tires with higher numerical values assigned to tires featuring stronger, heavier duty constructions.

Today's load range/ply ratings do not count the actual number of body ply layers found inside the tire, but indicate an equivalent strength based on early bias ply tires. Most radial passenger tires have one or two body plies, and light truck tires, even those with heavy duty ratings (10-, 12- or 14-ply rated), actually have only two or three fabric body plies, or one steel ply.

Passenger Tires

Since most passenger tires feature Standard or Standard Load Ranges, only Light Load, Reinforced and Extra Load tires are designated in the Tire Rack's descriptions.

• Standard Euro-metric tires will have nothing branded on their sidewalls, Extra Load or Reinforced Euro-metric tires will be branded as such and identified by an "RF" or "XL" in their descriptions, as in 305/50R20 XL or 305/50R20 RF.
• Standard Load P-metric tires will have nothing branded on their sidewalls or may be branded as "Standard Load," Light Load P-metric tires will be branded as "Light Load," and identified by an "LL" in their descriptions, as in P285/35R-19 LL. Additionally, Extra Load P-metric tires will be branded as "Extra Load," and identified by an "XL" in their descriptions, as in P235/75R-15 XL.

Only P-Metric sized tires with 45-series aspect ratios or lower may be manufactured in a Light Load configuration. Light Load tires are designed to carry less weight than Standard Load tires and have been developed for specific applications (typically when relatively large tire sizes are used as Original Equipment (O.E.) on relatively small cars or for Track & Competition DOT tires used for racing applications).

In all cases, when changing tire sizes or converting from Euro-metric sizes to P-metric sizes, it is important to confirm that the Load Index in the tire's Service Description of the new tire is equal to or greater than the Load Index of the original tire.

Light Truck Tires

Since light truck tires are often available in multiple load ranges, the appropriate load range is identified immediately following the size's rim diameter in the Tire Rack's descriptions.

• LT-metric, LT-Flotation and LT-numeric tires will be branded with their load range ("Load Range E" or "LRE") or their ply rating ("10 Ply Rated") on their sidewalls and list their appropriate load range letter in their descriptions as LT245/75R-16E, 7.50R-15D or 31x10.50R-15C.
• ST-metric sized special trailer service tires will be branded with their load range ("Load Range D" or "LRD") on their sidewalls and list their appropriate load range letter in their descriptions as ST205/75R15 LRD.

Common passenger, light truck and special trailer tire load ranges, equivalent ply ratings and load inflation pressures for radial ply tires are shown below:

Load Range and Load Pressure for Passenger Tires

	Load Range	Load Pressure (psi)
P-metric	Light Load Standard Load Extra Load	35 35 41
Euro-metric	Standard Reinforced/Extra Load	36 42

Load Range, Ply Rating and Load Pressure for Light Truck Tires

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

*Selected large Flotation LT sized tires have reduced load pressures from the values shown above.

Load Range, Ply Rating and Load Pressure for Light Truck Tires

	Load Range	Ply Rating	Load Pressure (psi)
ST-metric	B C D	4 6 8	35 50 65

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