An adjustable speed effort-saving bicycle, comprising a front wheel assembly (1), a rear wheel assembly (2), and a bicycle frame (3), the front wheel assembly (1) and the rear wheel assembly (2) being mounted respectively on either the front or rear end of the vehicle frame (3), also comprising a quad-connecting rod mechanism, a chain wheel (4), chain A (5), and a transmission mechanism for use in converting the weight of a rider into a rocking force. The quad-connecting rod mechanism is mounted on the bicycle frame (3). The chain wheel (4) is rotatably mounted on the bicycle frame (3) and meshes with the middle part of chain A (5). The chain wheel (4) is transmissively connected to the rear wheel assembly (2) via a transmission apparatus. One end of chain A (5) is slidably connected to an output frame-connecting rod (6) of the quad-connecting rod mechanism. A bent part (7) extends from a connecting end of the output frame-connecting rod (6) to the bicycle frame (3). The other end of chain A (5) is connected to the bent part (7). A tensioner (8) used for tensioning chain A (5) is provided between the bent part (7) and the output frame-connecting rod (6). The bicycle allows the speed to be adjusted easily and quickly and safeguards the physical and mental health of the rider.
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