The required load-capacity-index does not indicate the gross weight rating, rather the maximum axle load. Thereby, the sum of all the axle loads is at least equal, mostly however, it is higher than the gross weight rating. This allows the axles to be differently burdened depending on the nature of the load.
The carrying capacity of a tyre is expressed by the Load-Index. The LI divides the maximum portable mass into various classes. It does not increase symmetrically with the respective mass, rather, the differences to the next highest class become greater. They change, e.g., shown in the table from 7 kg up to 50 kg.
The load-index is bound to a precise specification, the same as, e.g, tyre-pressure and camber. Should these specifications be exceeded, then a safety surcharge must be taken into account. The prescribed load-index must be coordinated between the vehicle- and the tyre manufacturer.
Instead of the load index there used to be the description, "reinforced"..