A motor-driven chair for propelling a user over an underlying surface, the chair comprising: (a) a seat element having support surfaces for supporting the user sitting in a seat-facing direction; (b) a seat pole extending downwards from said seat element for supporting said seat element, said seat pole defining a vertical axis ; (c) a drive wheel rotatable about a horizontal axis of rotation so as to define a direction of forward motion perpendicular to said axis of rotation, said drive wheel being located beneath said seat element substantially on said vertical axis, said drive wheel being mechanically linked to said seat pole so as to maintain said direction of forward motion aligned with said seat-facing direction so that rotation of said seat element about said vertical axis causes a corresponding rotation of said direction of forward motion; (d) a motor in driving connection to said drive wheel so as to drive said drive wheel to rotate about said horizontal axis of rotation, and thereby propel the chair in the seat-facing direction; (e) a stabilizer assembly mechanically linked to said seat pole, said stabilizer assembly comprising a set of stabilizer wheels mounted on a support structure for supporting said seat pole in a vertical orientation, said stabilizer assembly allowing rotation of said seat pole about said vertical axis relative to said support structure; and (f) a suspension arrangement associated with said seat pole, said drive wheel and said stabilizer assembly, characterized in that said suspension arrangement comprises a first suspension spring deployed to transfer load between said seat pole and said drive wheel and a second suspension spring deployed to transfer load between said seat pole and said support structure or said suspension arrangement comprises a first hydraulic arrangement comprising at least one piston , said first hydraulic arrangement being deployed to transfer load between said seat pole and said drive wheel, and a second hydraulic arrangement comprising at least one piston , said second hydraulic arrangement being deployed to transfer load between said seat pole and said support structure, wherein said first and second hydraulic arrangements are interconnected by a pressure-equalization line , thereby distributing a load of the user sitting stably on said seat element so as to maintain a predefined range of proportions between a load supported by said drive wheel and a load supported by said stabilizer wheels. (a) a seat element having support surfaces for supporting the user sitting in a seat-facing direction; (b) a seat pole extending downwards from said seat element for supporting said seat element, said seat pole defining a vertical axis ; (c) a drive wheel rotatable about a horizontal axis of rotation so as to define a direction of forward motion perpendicular to said axis of rotation, said drive wheel being located beneath said seat element substantially on said vertical axis, said drive wheel being mechanically linked to said seat pole so as to maintain said direction of forward motion aligned with said seat-facing direction so that rotation of said seat element about said vertical axis causes a corresponding rotation of said direction of forward motion; (d) a motor in driving connection to said drive wheel so as to drive said drive wheel to rotate about said horizontal axis of rotation, and thereby propel the chair in the seat-facing direction; (e) a stabilizer assembly mechanically linked to said seat pole, said stabilizer assembly comprising a set of stabilizer wheels mounted on a support structure for supporting said seat pole in a vertical orientation, said stabilizer assembly allowing rotation of said seat pole about said vertical axis relative to said support structure; and (f) a suspension arrangement associated with said seat pole, said drive wheel and said stabilizer assembly, <EOS>