Abstract: A seat support structure of a bicycle comprises a seat supporting tube; a seat supporting rod received in the seat supporting tube; a lower lateral side of the seat supporting rod having a first inclined surface; the seat supporting rod being formed with an upper hole and a lower tapered hole; a tightening assembly received in the seat supporting tube; the tightening assembly having a tightening unit, an embedding unit; and a stud; in assembly, a screw post of a stud passes through the upper hole, the lower tapered hole, the stud hole of the tightening assembly and the embedding hole of an embedding hole so as to combine the tightening assembly to the seat supporting rod; then the seat supporting rod and the tightening assembly are placed within the seat supporting tube.

Abstract: A bicycle seat tube adjusting assembly includes: a rod body which is installed with a positioning seat; a first clamping unit and a second clamping unit being assembled with the positioning seat; two channels being formed between the first clamping unit and the second clamping unit for clamping; an adjusting unit installed with the second clamping unit; the adjusting unit having at least one protrusion and at least one tightening unit abutting against the protrusion; and a positioning unit resting against the positioning seat; and wherein by the adjusting unit, the first clamping unit and second clamping unit are adjusted on the positioning seat so as to provide a preferred riding position.