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 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 ; 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 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 ; 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 . <EOS>