A bicycle seat position changer is provided which allows the rider to quickly change the effective seat tube angle of the bicycle without requiring the use of tools. The seat position changer allows the rider to move the seat between a forward position and a rearward position, allowing a rider to select a more aerodynamic position or a traditional road position while riding, as required for comfort or by riding conditions. The seat position changer allows the rider to adjust the seat position between the forward and rearward positions while maintaining a consistent difference in seat-to-bottom-bracket length. In one embodiment the consistent difference in seat-to-bottom-bracket length is close to zero and imperceptible to the rider.