What is load range?
Load range is the modern day practice which is equivalent to the use of ply ratings which originally was employed to rate the relative strength of one tire compared with another.
Initially tires were made using a number of different layers, or plies, that combined cords with other materials. The greater the number of plies, the stronger the tire was and that meant that it could be inflated with a higher air pressure and carry a heavier load.
Today physical plies have been replaced with thinner stronger materials and it isn't necessary to have 6 or 8 or 10 or 12 different layers inorder to give the same strength that was available when cotton cords were used. So, today you hear the term "ply rating X" which means that the tire has the same strength as a tire that used to be made with X number of cords. That tire may only have one or two physical plies but could be rated as the equivalent of a much higher ply rating.
Passenger tire often use load ranges with specific names, while tires made for light trucks utilize a series of letters to designate the load that the tire is designed to carry. The higher the letter, the heavier to load.
When you need to change to a different size or type of tire from what your vehicle originally came with, it is important to make sure that the Load Index of your new tire is at least the same or more than what your originally used so the tire is capable of carrying the weight which your vehicle is designed to support.
Most P-Metric passenger tires are made to carry what is called Standard Load and have nothing on their sidewalls which indicate this or, in some cases, they may be identified using "SL" in their descriptions, such as P225/70R-15 SL.
If a P-Metric tire is designed to carry extra weight it would be called Extra Load, and carry the letters XL in their descriptions, as in P225/70R-15 XL.
There is a Light Load classification which may be applied to low profile tires with an aspect ratio or 45 or less. These tires are marked with the leters LL in their size description such as P285/40R-20 LL.
In Europe, Extra Load tires are designated as Reinforced tires and may carry a marking of "RF" instead of "XL".
|Light Load||LL||35 psi or (240 kPa)|
|Standard Load||Nothing or SL||35 psi or (240 kPa)|
|Extra Load||XL||41 psi or (280 kPa)|
Euro-Metric Passenger Vehicle Tires
|Load Ranges||Abbreviated||Max Load Pressure||kPa|
|Standard Load||Nothing or SL||36 psi||(250 kPa)|
|Extra Load||RF or XL||42 psi||(290 kPa)|
Since tires for light trucks and Trailer Service tire (ST) are often offered in different load ranges, the load range is stamped immediately after the size's rim diameter.
LT-Metric, LT-Flotation and LT-Numeric tires are 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:
|Load Range||Ply Rating||Max Load Pressure|
|B||4||35 psi (240 kPa)|
|C||6||50 psi (350 kPa)|
|D||8||65 psi (450 kPa)|
|E||10||80 psi (550 kPa)|
|F||12||95 psi (650 kPa)|
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