Load Range SL is a designation for tires that stands for Standard Load. It is a common load range for regular, lightweight vehicles and passenger cars. SL tires are designed to handle the exact load pressure mentioned on the tire sidewalls numbers, receiving no extra reinforcement for the interior structure. The load capacity of an SL tire will not increase if you pump the tires to over 35 PSI. SL tires are not suitable for trucks or vehicles that carry heavy loads. They are designed primarily for passenger cars that are used on a daily basis and do not need to carry or bear significant weights. The load range of a tire is imprinted on its sidewall and indicates the amount of load it has been designed to carry at the pressure specified by the manufacturer.