Disclosed are various exemplary embodiments of a multi-piece rim assembly for mounting a tire. The rim assembly may include a rim base having a first end and a second end, a flange detachably mountable to the first end of the rim base, and a flange assembly detachably mountable to the second end of the rim base. The flange and the rim base may cooperatively define a first bead seat for receiving a first bead of the tire, and the flange assembly may define a second bead seat for receiving a second bead of the tire. The flange assembly may be formed of a unitary construction that includes a bead seat section having an outer surface for contacting a bottom edge of the second bead of the tire and a flange section extending substantially radially outwardly from the bead seat section to contact a side wall of the second bead of the tire. The rim assembly may also include a lock ring configured to secure the flange assembly to the rim base.