Abstract: A powereed riding tractor lawn mower suited to uneven terrain has four fluid motor powered driven wheels and includes a frame comprising front and rear frame sections connected for pivoting about a first axis between the sections and normal to the ground plane. The rear frame section is in turn made up of forward and rearward portions, the rearward portion of which pivots about a second axis which intersects and is perpendicular to the first axis enabling the rear wheels to pivot about both axis. Sterring is accomplished by a steering mechanism which changes the angular relation of the frame sections.