Load ratings are very important and it is the law to install the proper rated tire on your vehicle. Each vehicle will have a placard on the door or elsewhere which will provide you with the proper recommended size as well as a load rating if applicable. The size will have a letter after it which is the load rating. If there is no letter then your vehicle requires a standard passenger tire which is a 4 ply. Some 1/2 ton trucks only require passenger tires but many people will install tires that are rated C or d and that is okay. Remember you can go up just not down. Now we will look at what each load rating stands for.
B Load rating or Standard load A Load rating of B is generally not found however it does designate a 4 ply which is equivalent to a passenger tire or more commonly known as standard load. The max pressure is 35 psi.
XL or Extra Load An XL tire has a thicker sidewall and is commonly used for smaller trucks or vans that are used to carry heavy loads. Usually an XL tire does not come stock except for some vans. The max pressure for an XL tire is 41 psi.
LT truck tires load range C,D and E When we get into light truck tires found generally on ¾ ton trucks and above the load ratings are designated by the number of plies the tire has. Below we will give the descriptions of each.
Load Range C are 6 ply tires commonly found in sizes such as 31x1050x15. The max pressure on this load rating is 50 psi
Load Range D are 8 ply tires and have a max pressure of 65 psi. Be careful and read your dor sticker carefully as most truck requiring LT tires require an E rating.
Load Range E are 10 ply tires are are the more popular LT Tires found as OEM on light trucks. The max pressure rating of these is 80 psi.
Trailer Tires Trailer tires are rated similar to truck tires except instead of LT trailer tires will have an ST with a letter after it the corresponding letter represents the amount of plies such as B (4 plies) and C (6 plies). The max pressure is the same as light truck tires.
What pressure to run?
For most tires it is recommended to run at or just below that max tire pressure for safety and to ensure your tires wear quickly. If you own a light truck and do not run it loaded you can get away with running 65 lbs instead of 80 for a little better ride. Also it is important to mention the fact that installing LT tires on a ½ ton or lower truck will give you a very stiff ride because of the extra plies so it is recommended to stick to the recommended tires as LT tires are overkill.