A motor vehicle, including: (a) a body, (b) a motor adapted to propel said motor vehicle, (c) a set of wheels (124a-124d) for supporting said motor vehicle on a roadway, said set of wheels comprising: a pair of front wheels (124a, 124b); and a pair of rear wheels (124c, 124d); wherein said set of wheels defines a set of corner areas of said motor vehicle, (d) a suspension system connecting said body with each of said wheels, said suspension system being adapted to permit relative displacement between said wheels and said body, (e) a movable underbody adapted to do at least one of the following: (i) produce downforce, and (ii) reduce aerodynamic drag; said movable underbody including a corresponding set of corner areas, wherein said movable underbody is not fixed to said body, (f) a suspension-mounted support means for dynamically supporting said movable underbody such that said movable underbody maintains a more constant distance and orientation above a roadway being traversed than maintained by said body, and (g) a retraction means (111, 110, 160) for elevating and lowering said movable underbody relative to said body, wherein elevation of said movable underbody to said body functionally disengages said movable underbody from said suspension system so that said movable underbody is fixed against the undersurface of said body, and wherein lowering of said movable underbody away from said body functionally engages said movable underbody with said suspension system so that said movable underbody displaces vertically and substantially relative to said body with said set of wheels. (a) a body, (b) a motor adapted to propel said motor vehicle, (c) a set of wheels (124a-124d) for supporting said motor vehicle on a roadway, said set of wheels comprising: a pair of front wheels (124a, 124b); and a pair of rear wheels (124c, 124d); wherein said set of wheels defines a set of corner areas of said motor vehicle, a pair of front wheels (124a, 124b); and a pair of rear wheels (124c, 124d); (d) a suspension system connecting said body with each of said wheels, said suspension system being adapted to permit relative displacement between said wheels and said body, (e) a movable underbody adapted to do at least one of the following: (i) produce downforce, and (ii) reduce aerodynamic drag; said movable underbody including a corresponding set of corner areas, wherein said movable underbody is not fixed to said body, (i) produce downforce, and (ii) reduce aerodynamic drag; (f) a suspension-mounted support means for dynamically supporting said movable underbody such that said movable underbody maintains a more constant distance and orientation above a roadway being traversed than maintained by said body, and (g) a retraction means (111, 110, 160) for elevating and lowering said movable underbody relative to said body, wherein elevation of said movable underbody to said body functionally disengages said movable underbody from said suspension system so that said movable underbody is fixed against the undersurface of said body, and wherein lowering of said movable underbody away from said body functionally engages said movable underbody with said suspension system so that said movable underbody displaces vertically and substantially relative to said body with said set of wheels. wherein elevation of said movable underbody to said body functionally disengages said movable underbody from said suspension system so that said movable underbody is fixed against the undersurface of said body, and wherein lowering of said movable underbody away from said body functionally engages said movable underbody with said suspension system so that said movable underbody displaces vertically and substantially relative to said body with said set of wheels.