A seat attaching may include a lower seat clamp that is moveable relative to a post head member about a pivot axis and includes: a mounting portion having a bearing surface configured to engage a corresponding cradle portion of the post head member a first channel configured to receive a first seat rail of a bicycle seat and a second channel configured to receive a second seat rail of a bicycle seat. An upper seat clamp may include: a central portion overlying the mounting portion; a first extension portion disposed on a first side of the central portion and having a first retainer surface overlying and facing the first channel to retain the first seat rail within the first channel and having a first apex; and a second extension portion disposed on a second side of the central portion and having a second retainer surface overlying and facing the second channel to retain the second seat rail within the second channel and having a second apex. An upper plane may contain both the first apex and second apex and may be substantially parallel to the pivot axis. The upper plane may be offset below the pivot axis and intersecting the bearing surface. A first fastener may be used to secure the upper seat clamp to the post head member.