A method is provided for assembling a vehicle frame from hydro-formed tubular metal components. Each hydro-formed component has a surface feature that is complementary to a surface feature on an adjacent component. The complementary surface features allow the hydro-formed components to be interlocked together. The components are permanently joined by a plurality of welds. A front hoop, a rear hoop and right and left side hoops may be assembled and joined together to form the passenger compartment portion of the vehicle frame.