What Does a Load Range of SL on a Truck Tire Mean?

There is a lot of important information, including load range, ply rating and type of tire printed on the side of new tires. The load range, maximum load pressure or load index indicates the maximum amount of weight a tire can safely carry with standard air pressure without having a blow out. The load capacity of tires becomes especially important on heavy duty trucks, which are often used to carry heavy loads, go off-road and tow passenger vehicles.

Function

Modern tires are given a tire rating based on the tire's size, construction, speed rating, load-carrying capacity and inflation pressure. P-metric sized tires--passenger tires with sizes starting with a "P" such as P235/75R15--are given a load range rating of either SL or XL. SL stands for Standard Load and XL indicates extra load. An SL-rated tire has its maximum load capacity at an inflation pressure of 35 psi. XL tires can carry a heavier load when inflated to 41 psi.

Identification

The maximum load capacity in pounds will be listed on the tire sidewall or in tire load/inflation charts. All SL-rated tires of the same size will have the same load capacity. For example, all P235/75R15 SL tires have a maximum load capacity of 2,018 pounds.

Warning

The load capacity for P-metric tire sizes (ply tires) is for passenger cars. If a P-metric tire is mounted on a truck or SUV, the maximum load capacity is reduced by 9 percent. If our P235/75R15 tires are used on a truck or SUV, the maximum load per tire is 2,028 times 91 percent or 1,845 pounds. The total weight for the vehicle should not exceed 7,380 pounds. The load capacity of an SL load range tire does not increase by inflating the tire to more than 35 psi. The tire will have a maximum tire pressure lifespan greater than 35 psi, but the max load capacity is reached at 35 psi.

Considerations

There are several ways to provide your truck with a higher load capacity. XL tires instead of SL tires will add about 140 pounds of capacity per tire. Larger tire sizes will have higher load capacity. Switch from P-metric tires to light truck tires with load ranges listed as C, D or E. These tires have maximum loads at inflation pressures of 50, 65 and 80 psi respectively and are not load-downgraded for truck use. For example, a light truck tire size 255/75R15 load range C has a load capacity of 2,270 pounds, over 400 pounds more that the P235/75R15 SL P-metric tire when used on a truck.

Significance

SL-rated tires are the lowest light load capacity tires that are used on trucks and SUVs. If your truck has load range SL tires, consider upgrading the tire load capacity, or be careful how much cargo you haul in your truck. With the right tires, pickup trucks could easily carry their maximum weight with the best fuel efficiency the original equipment can muster.