The invention relates to a ring (120) that is intended for being mounted tightly around a shaft of a hydraulic machine to form a portion of a hydrostatic or hydrodynamic bearing. The ring includes at least one first section (122), at least one second section (124) and means (132) for mounting the first and second sections around the shaft. Each section (122, 124) includes two edge surfaces (1223, 1243) connecting the external (1221, 1241) and internal (1222, 1242) radial surfaces thereof. The first section (122) is provided with at least one threaded hole (127) accessible via an edge surface (1223) and capable of receiving a screw (132) projecting from an edge surface (1243) of the second section (124). The screw (132) is provided, on the portion of the shank (134) thereof that projects from the second section (124), with at least one raised pattern (140) for rotatably moving the shank (134) in order to screw or unscrew the shank in the threaded hole (127). The screw (132) is provided with a piston (130) sliding in a recess (128) arranged in the second section (124), connecting to the edge surface (1243) of the second section and isolated from the outside by a bearing (136). The second section (124) is provided with means for supplying pressurized fluid to a chamber (C1) with variable volume arranged between the piston (130) and the bearing (136), inside the recess (128).