How much does a liquid loaded tractor and trailer weigh?

Unless you're servicing oil wells, the maximum any tractor-trailer can weigh is 80,000 pounds--with 20,000 pounds on the steer axle (although it will NEVER get this high) and 34,000 pounds on the tandems. Oil well servicing trucks are different: because of the nature of the product they carry--salt water off the wells, which is super heavy and they don't have scales at the wells--those guys are basically given unlimited gross vehicle weight.