An integral rim (J') having frustoconical seats (2') inclined 15.degree..+-.1.degree., the axial widths (P') of which are greatly decreased as compared with the axial widths (P) of the known frustoconical seats (2), and having a mounting groove (3') of reduced height (H') so as to permit an increase in the space available for the braking means. The assembly of a rim (J') as described above and of a tire (T) having beads the tips of which have been truncated permits better resistance of said beads to fatigue while permitting easy mounting. The invention is employed for tires and rims intended for heavy vehicles.