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 that tells you the proper recommended size, as well as a load rating, if applicable. The size will have a letter after it which is the load capacity. If there is no letter, then your vehicle requires a standard passenger tire that is 4-ply. Some 1/2 ton trucks only require passenger tires, but many people will install C ody rated tires and that’s fine. Remember that you can go up but not down. Now we will see what each load index represents.
B Load capacity or standard load A load rating of B is not usually found; however, it designates a 4-ply tire that is equivalent to a passenger tire or more commonly known as a standard cargo. The maximum pressure is 35 psi.
XL or Extra Load An XL tire has a thicker sidewall and is commonly used for smaller trucks or vans used to carry heavy loads. An XL tire does not usually come stock, except on some trucks. The maximum pressure for an XL tire is 41 psi.
Load range of LT C, D and E truck tires When we get into light truck tires typically found on trucks ¾ ton and up, load capacities are designated by the number of plies the tire has. Next we will give the descriptions of each one.
Load Range C are 6 ply tires commonly found in sizes like 31x1050x15. Maximum pressure at this load rating is 50 psi
Load Range D are 8 ply tires and have a maximum pressure of 65 psi. Please be careful and read the sticker on your dor carefully as most trucks that require LT tires require an E rating.
Load Range E are 10 ply tires which are the most popular LT tires found as OEMs on light trucks. The maximum 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 representing the number of ply, such as B (4 ply) and C (6 layers). The maximum pressure is the same as that of light truck tires.
What pressure to run?
For most tires it is recommended to run at or just below maximum tire pressure for safety and to ensure tires wear quickly. If you own a light truck and don’t drive it loaded, you can run on 65 pounds instead of 80 for a slightly better ride. Also important to mention is the fact that fitting LT tires on a ½ ton truck or less will give it a very stiff ride due to the extra plies, so sticking to the recommended tires is recommended as LT tires are over the top.