Tire Load Index
A numerical code on a tire's sidewall that specifies the maximum weight capacity the tire can support.
A tire load index is a numerical code printed on the tire sidewall, adjacent to the speed rating, that indicates the maximum weight capacity the tire can support when inflated to its maximum safe pressure. The index numbers correspond to a standardized chart: for example, a load index of 90 indicates the tire can carry up to 1,323 pounds (600 kg), while a load index of 100 indicates a capacity of 1,984 pounds (900 kg).
Multiplying the capacity of a single tire by four gives the total load-carrying capacity of the set, which must exceed the gross vehicle weight rating (GVWR) of the vehicle. Light trucks and SUVs often require reinforced (XL) or light truck (LT) tires with higher load indices to handle heavy cargo and towing loads.
Installing tires with a lower load index than specified by the manufacturer is a severe safety hazard. The excessive weight will cause the tires to overheat and flex excessively, leading to rapid tread wear, bead damage, and potential tire blowout at highway speeds. Mechanics verify the load index when recommending replacement tires.