A bicycle seat post assembly comprising: a seat post having a head portion and a stem portion, the stem portion having an elongate shape formed about a longitudinal axis and adapted to cooperate with a seat tube of a bicycle frame; a passage having a first section and a second section, the first and second sections (132, 134) each being formed through the head portion about respective axes that are oriented in a crossing direction relative to the longitudinal axis of the stem portion; a collar positioned in the passage and adapted to attach a bicycle seat to the bicycle frame, the collar having first and second portions (194, 196); and a shock member positioned in the passage between the collar and the head portion that dampens movement of the bicycle seat relative to the bicycle frame, wherein the shock member comprises a first shock member section and a second shock member section, characterized in that the shock member defines a shock member passage having a first shock member passage portion and a second shock member passage portion; wherein the collar is received in the shock member passage, such that the first collar portion cooperates with the first shock member passage portion and the second collar portion cooperates with the second shock member passage portion; and a hinge formed by the second section of the passage, second portion of the collar and second shock member section, that connects the collar and the head portion of the seat post and is located along a circumferential interface between the collar and head portion and defines an axis of rotation of the collar with respect to the head portion. a seat post having a head portion and a stem portion, the stem portion having an elongate shape formed about a longitudinal axis and adapted to cooperate with a seat tube of a bicycle frame; a passage having a first section and a second section, the first and second sections (132, 134) each being formed through the head portion about respective axes that are oriented in a crossing direction relative to the longitudinal axis of the stem portion; a collar positioned in the passage and adapted to attach a bicycle seat to the bicycle frame, the collar having first and second portions (194, 196); and a shock member positioned in the passage between the collar and the head portion that dampens movement of the bicycle seat relative to the bicycle frame, wherein the shock member comprises a first shock member section and a second shock member section, characterized in that the shock member defines a shock member passage having a first shock member passage portion and a second shock member passage portion; wherein the collar is received in the shock member passage, such that the first collar portion cooperates with the first shock member passage portion and the second collar portion cooperates with the second shock member passage portion; and a hinge formed by the second section of the passage, second portion of the collar and second shock member section, that connects the collar and the head portion of the seat post and is located along a circumferential interface between the collar and head portion and defines an axis of rotation of the collar with respect to the head portion.