S.C. Code Ann. § 56-5-4130: Wheel and axle loads; high and low pressure tires.

(A)(1) The gross weight upon any wheel of a vehicle shall not exceed eight thousand pounds when equipped with high-pressure pneumatic, solid rubber or cushion tires, nor ten thousand pounds when equipped with low-pressure pneumatic tires. The gross weight upon any one axle of a vehicle shall not exceed sixteen thousand pounds when equipped with high-pressure pneumatic, solid rubber or cushion tires, nor twenty thousand pounds when equipped with low-pressure pneumatic tires.

(2) On the interstate and noninterstate highways of this State, any over-the-road bus as defined by Title 49 of the United States Code, motorhome, or any vehicle which is regularly and exclusively used as an intrastate public agency transit passenger bus as defined by Title 49 of the United States Code, is excluded from the axle weight limits in item (1). However, these vehicles are limited to a maximum single axle weight limit of twenty-four thousand pounds, including all enforcement tolerances.

(B) For the purpose of this section an "axle load" shall be defined as the total load transmitted to the road by all wheels whose centers may be included between two parallel transverse vertical planes forty inches apart, extending across the full width of the vehicle, every pneumatic tire designed for use and used when inflated with air to less than one hundred pounds pressure shall be deemed a "low-pressure tire" and every pneumatic tire inflated to one hundred pounds pressure or more shall be deemed a "high-pressure tire".