The method of building and transferring a tread belt structure on a portable and collapsible building drum 10 mounted coaxially on a building machine 100 with a rotatable shaft 120 is disclosed. The method includes the steps of forming the annular tread belt 4 on the building drum 10, transferring the building drum 10 with the tread belt 4 from the rotatable shaft 120 onto a pivoting transfer device 200, pivoting the transfer device 200 about 90° rendering the tread belt 4 and axis of the building drum 10 perpendicular to a horizontal plane, collapsing the building drum 10, separating the annular tread belt 4 from the building drum 10, removing the tread belt 4, expanding the tire building drum 10, pivoting the building drum 10 into coaxial alignment with the rotatable shaft 120, moving the building drum 10 onto the shaft 120. The tread belt 4 has one or more elastomeric components applied while hot and the equipment provides means for weighing the tread belt 4.