Method of manufacturing a vehicle body and frame assembly

A method for forming a closed channel structural member having a central portion that is enlarged relative to the end portions thereof is disclosed. Initially, first and second tubes 10, 20 are formed in respective hydroforming dies 11, 21 to have desired shapes that are preferably characterized by a relatively large diameter first end portions 15, 25 and relatively small diameter second end portions 16, 26. Each of the two tubes 10, 20 is then oriented such that the relatively large diameter first end portions 15, 25 are disposed adjacent to one another. Lastly, the relatively large diameter first end portion 15, 25 are joined together in any conventional manner, such as by butt welding, to form a unitary member 30 characterized by a relatively large diameter central portion extending between a pair of relatively small diameter end portions. The unitary member can be used as a component, such as a side rail, of a vehicle body and frame assembly.