Abstract: An adjustable bicycle seat which is supported on a seat tube. The seat is vertically adjustable and held in place by a clamp. A spring is located within the tubular seat frame. The lower end of the spring is supported within the tubular seat frame. A seat tube clamp is positioned about the tubular seat frame which adjustably holds the seat tube at a desired height. Means are provided for limiting the upward movement of the seat to retain the seat tube within the tubular seat frame.

Abstract: A replacement unit for a conventional bicycle which can be installed without modifying the bicycle requires the original seat and seat shaft to be taken out of the bicycle frame and replaced by the replacement unit. This unit comprises a tube which fits inside the vertical tubular bicycle frame. Inside the tube is a coil spring and a shaft. The coil spring is compressed by the weight of the shaft, and the weight rider sitting on the seat. When the rider places his weight on the pedals, the spring inside the tube lifts the seat. A plurality of stop members are disposed along the shaft and a pin is positioned to engage the stop member to lock the seat at the correct height above the frame, depending on the needs of the driver.

Abstract: A hollow seat post has a seat attached at one end while the opposite end is split defining an aligning pin receiving groove. One portion of the split end is provided with longitudinally spaced pin receiving holes. A coil spring is inserted inside a frame seat post. A small pin extending through the bottom of the frame seat post serves as a stop for the coil spring. A second pin extends through the upper portion of the frame seat post and aligns the seat when the seat post is inserted inside the frame seat post with the second pin in the groove in the seat post. A lever actuated pin is mounted on the frame and is positioned so the pin is in alignment with a hole extending through the frame seat post and can move therein. When the seat post is inserted in the frame seat post and the hole in the frame seat post is aligned with one of the holes in the seat post, the lever actuated pin penetrating both holes holds the seat at the desired level.