A wheelchair includes a frame, a seat attached to the frame, a first forward wheel on a first side of the frame and a second forward wheel on a second side of the frame, a first rearward wheel on the first side of the frame and a second rearward wheel on the second side of the frame, a first drive wheel on the first side of the frame positioned intermediate between the first forward wheel and the first rearward wheel and a second drive wheel on the second side of the frame positioned intermediate between the second forward wheel and the second rearward wheel, and actuators to independently control the vertical position of the first forward wheel relative to the frame, the vertical position of the second forward wheel relative to the frame, the vertical position of the first rearward wheel relative to the frame, the vertical position of the second rearward wheel relative to the frame, the vertical position of the first drive wheel relative to the frame and the vertical position of the second drive wheel relative to the frame.