Cycle comprising: - a frame mounted on wheels (5, 6) and comprising a saddle-guiding tube, - a saddle supported by a seat post that is mounted such that it slides in the guiding tube, - a saddle-adjusting mechanism comprising: -- an open clamping collar arranged about the guiding tube and comprising first and second ends (14, 15) capable of being moved closer to one another while clamping the guiding tube on the seat post, whereby at least the first end has an outer face provided with a first helical cam surface, -- a lever mounted such that it pivots on the first and second ends of the clamping collar about a rotational axis that is substantially perpendicular to the seat post, the lever having a second helical cam surface arranged facing the first helical cam surface, the lever being capable of being actuated by pivoting by a user in first and second opposite directions (S1, S2) to selectively clamp and unclamp the clamping collar, characterised in that it further comprises a sliding washer made of a material with a low coefficient of friction, inserted between the first and second helical cam surfaces, the sliding washer being open and having a helical shape corresponding to the shapes of the first and second helical cam surfaces (25, 26), whereby the first and second helical cam surfaces (25, 26) and the sliding washer each have a substantially frustoconical shape, forming an angle (α) that deviates from the rotational axis by 90 degrees. - a frame mounted on wheels (5, 6) and comprising a saddle-guiding tube, - a saddle supported by a seat post that is mounted such that it slides in the guiding tube, - a saddle-adjusting mechanism comprising: -- an open clamping collar arranged about the guiding tube and comprising first and second ends (14, 15) capable of being moved closer to one another while clamping the guiding tube on the seat post, whereby at least the first end has an outer face provided with a first helical cam surface, -- a lever mounted such that it pivots on the first and second ends of the clamping collar about a rotational axis that is substantially perpendicular to the seat post, the lever having a second helical cam surface arranged facing the first helical cam surface, the lever being capable of being actuated by pivoting by a user in first and second opposite directions (S1, S2) to selectively clamp and unclamp the clamping collar, characterised in that it further comprises a sliding washer made of a material with a low coefficient of friction, inserted between the first and second helical cam surfaces, the sliding washer being open and having a helical shape corresponding to the shapes of the first and second helical cam surfaces (25, 26), whereby the first and second helical cam surfaces (25, 26) and the sliding washer each have a substantially frustoconical shape, forming an angle (α) that deviates from the rotational axis by 90 degrees. -- an open clamping collar arranged about the guiding tube and comprising first and second ends (14, 15) capable of being moved closer to one another while clamping the guiding tube on the seat post, whereby at least the first end has an outer face provided with a first helical cam surface, -- a lever mounted such that it pivots on the first and second ends of the clamping collar about a rotational axis that is substantially perpendicular to the seat post, the lever having a second helical cam surface arranged facing the first helical cam surface, the lever being capable of being actuated by pivoting by a user in first and second opposite directions (S1, S2) to selectively clamp and unclamp the clamping collar,