An adjustable suspension for a bicycle, comprising: - a suspension body provided with a main fluid inlet configured to inject a fluid into the suspension body, and with a fluid outlet; - a piston disposed in the suspension body and comprising a piston head delimiting a first chamber and a second chamber inside said suspension body, the first chamber being in fluid communication with the main fluid inlet, the piston being movable in translation in the suspension body between: at least one first position in which the fluid outlet fluidly communicates with the second chamber but not with the first chamber, so as to deploy the piston, and at least one second position in which the fluid outlet is in fluid communication with the first chamber so that the fluid injected through the main fluid inlet is guided to the fluid outlet, in order to evacuate the injected fluid from the suspension, the piston being configured to move from the first position to the second position when fluid is injected through the main fluid inlet; and - a valve device which can assume a first state in which it prevents fluid from escaping from the suspension, and a second state in which it allows the extraction of the fluid from the suspension, characterized in that the valve device is configured to be brought into the second state when a fluid is injected through the main fluid inlet and to be brought into the first state when the fluid injection is interrupted - a suspension body provided with a main fluid inlet configured to inject a fluid into the suspension body, and with a fluid outlet; - a piston disposed in the suspension body and comprising a piston head delimiting a first chamber and a second chamber inside said suspension body, the first chamber being in fluid communication with the main fluid inlet, the piston being movable in translation in the suspension body between: at least one first position in which the fluid outlet fluidly communicates with the second chamber but not with the first chamber, so as to deploy the piston, and at least one second position in which the fluid outlet is in fluid communication with the first chamber so that the fluid injected through the main fluid inlet is guided to the fluid outlet, in order to evacuate the injected fluid from the suspension, the piston being configured to move from the first position to the second position when fluid is injected through the main fluid inlet; and at least one first position in which the fluid outlet fluidly communicates with the second chamber but not with the first chamber, so as to deploy the piston, and at least one second position in which the fluid outlet is in fluid communication with the first chamber so that the fluid injected through the main fluid inlet is guided to the fluid outlet, in order to evacuate the injected fluid from the suspension, the piston being configured to move from the first position to the second position when fluid is injected through the main fluid inlet; and - a valve device which can assume a first state in which it prevents fluid from escaping from the suspension, and a second state in which it allows the extraction of the fluid from the suspension, characterized in that the valve device is configured to be brought into the second state when a fluid is injected through the main fluid inlet and to be brought into the first state when the fluid injection is interrupted