A vehicle frame having a calibrated frame stiffness gradient is provided by fixedly attaching a series of cladding plates to an external surface of a tubular member of the frame, with the series of cladding plates including at least one immediately preceding cladding plate and one successive cladding plate. The cladding plates have thicknesses and peripheral shapes that are cooperatively configured to provide the desired stiffness gradient in the frame member. A trailing raised bead extending from the last cladding plate in the series along the surface of the frame member provides a further means for achieving the desired stiffness gradient.
