The rating of a truck is dependent on the total truck weight.
The Class 8 truck gross vehicle weight rating (GVWR) is a GVWR exceeding 33000 lb (14969 kg).
These also include tractor-trailer tractors, “straight-trucks” or single-unit dump trucks of a GVWR over 33,000 lb, as well as non-commercial chassis fire trucks; such trucks typically have 3 or more axles.