Run-flat device suitable for being used in a mounted assembly of a motor vehicle comprising a wheel rim having a rim bottom of diameter D and a tyre mounted on the wheel rim, the run-flat device being suitable for supporting the run-flat tyre and comprising: - a support ring (6, 6', 6") comprising a plurality of axial segments (7 and 7', 17 and 17', 27 and 27', 37, 57, 67, 77, 87 and 87', 97) that are juxtaposed on a circumference of the support ring and that define a radially inner mounting surface (7a, 17a, 27a) suitable for being mounted on said rim bottom and a radially outer support surface (7e, 17e and 17e', 27e, 77e) suitable for supporting the run-flat tyre, each of said segments having at least one bearing (12a and 12a', 22a and 22a', 32a and 32a') situated radially between said mounting surface and said support surface, and - at least one holding belt that encloses the support ring around said circumference in such a way as to hold it substantially in contact with the rim bottom and that passes through said segments, being applied against said at least one bearing of each of them, said segments not being articulated with each other and being contiguous or spaced apart from each other on the circumference by a total sum of consecutive spacings, measured between the segments at said mounting surface, that is less than π.D/2, said at least one holding belt having two belt ends (9a, 9b) spaced apart and connected to each other by connecting and locking means (10, 10' 10") capable of locking said at least one holding belt, this locking being able to ensure an advantageously adjustable clamping of said segments (7 and 7', 17 and 17', 27 and 27', 37, 57, 67, 77, 87 and 87', 97), characterised in that, over all or a portion of said circumference, said at least one bearing (12a, 22a and 22a', 32a and 32a') of each of said segments (7 and 7', 17 and 17', 27 and 27', 57, 67, 77) is formed: - at said belt ends (9a, 9b), by a radial reinforcement extending from said support surface (7e', 17e', 27e') and constituted of an axial bottom (12a', 32a') of a U-shaped recess or of a lateral axial shoulder of each segment, and - outside of said belt ends, by a radially inner edge (12a, 22a, 32a) of a space or through slot (12, 22, 32) that is provided radially withdrawn from said support surface (7e, 17e, 27e) and that opens out or not on at least one lateral surface (7d, 17d, 27d) of each segment. - a support ring (6, 6', 6") comprising a plurality of axial segments (7 and 7', 17 and 17', 27 and 27', 37, 57, 67, 77, 87 and 87', 97) that are juxtaposed on a circumference of the support ring and that define a radially inner mounting surface (7a, 17a, 27a) suitable for being mounted on said rim bottom and a radially outer support surface (7e, 17e and 17e', 27e, 77e) suitable for supporting the run-flat tyre, each of said segments having at least one bearing (12a and 12a', 22a and 22a', 32a and 32a') situated radially between said mounting surface and said support surface, and - at least one holding belt that encloses the support ring around said circumference in such a way as to hold it substantially in contact with the rim bottom and that passes through said segments, being applied against said at least one bearing of each of them, said segments not being articulated with each other and being contiguous or spaced apart from each other on the circumference by a total sum of consecutive spacings, measured between the segments at said mounting surface, that is less than π.D/2, said at least one holding belt having two belt ends (9a, 9b) spaced apart and connected to each other by connecting and locking means (10, 10' 10") capable of locking said at least one holding belt, this locking being able to ensure an advantageously adjustable clamping of said segments (7 and 7', 17 and 17', 27 and 27', 37, 57, 67, 77, 87 and 87', 97), characterised in that, over all or a portion of said circumference, said at least one bearing (12a, 22a and 22a', 32a and 32a') of each of said segments (7 and 7', 17 and 17', 27 and 27', 57, 67, 77) is formed: - at said belt ends (9a, 9b), by a radial reinforcement extending from said support surface (7e', 17e', 27e') and constituted of an axial bottom (12a', 32a') of a U-shaped recess or of a lateral axial shoulder of each segment, and - outside of said belt ends, by a radially inner edge (12a, 22a, 32a) of a space or through slot (12, 22, 32) that is provided radially withdrawn from said support surface (7e, 17e, 27e) and that opens out or not on at least one lateral surface (7d, 17d, 27d) of each segment.