Rear derailleur

A rear derailleur of a bicycle chain shift mechanism for the coaxial attachment—in terms of a rear axis on a bicycle frame rear tail of a bicycle, said rear derailleur comprising:

• a base element;
• a pivoting mechanism;
• a movable element;
• and
• a chain guide assembly;
• wherein the pivoting mechanism connects the base element to the movable element, and the chain guide assembly, the latter by a force-accumulating assembly being pretensioned, or able to be pretensioned, in a chain-tensioning direction, being connected to the movable element to be rotatable about a rotation axis;
• wherein the base element includes a first connecting end for the coaxial attachment—in terms of the rear axis—on the bicycle frame rear tail, and a second connecting end for coupling to the pivoting mechanism;
• wherein the first connecting end has a first arm and a second arm which in the axial direction are disposed to be mutually spaced apart and, by an associated adapter, are specified for assembling the derailleur on an assigned mounting portion of a rear tail of the bicycle frame rear tail;
• wherein, in a defined pre-assembled state and in a completely assembled state, the first arm is situated on an axial internal side of the mounting portion and the second arm is situated on an axial external side of the mounting portion;
• wherein the adapter includes an adapter bolt and an associated adapter nut that is able to be screwed to the adapter bolt and, in the defined pre-assembled state and in the completely assembled state, a bolt head of the adapter bolt is disposed on the axial external side of the mounting portion, and the adapter nut that is screwed to engage with the adapter bolt is disposed on the axial internal side of the mounting portion;
• and
• wherein, in the defined pre-assembled state, a rotational force is able to be exerted on the adapter nut by rotating the adapter bolt in a tightening direction, a consequential rotational force based on said rotational force by way of at least one entrainment formation of the adapter nut and at least one associated mating entrainment formation of the base element being able to be exerted on the base element which in the defined pre-assembled state is rotatable relative to the mounting portion in a first rotating direction corresponding to the tightening direction, said consequential rotational force acting counter to a counter rotational force exerted on the base element and, with the facilitation of a bicycle chain of the bicycle chain shift mechanism guided by the chain guide assembly, being exerted on the base element in a second direction counter to the first rotating direction;
• wherein at least one engagement element which facilitates an indirect frictional engagement between the adapter nut, on the one hand, and at least one of a) the first arm of the base element, b) the axial internal side of the mounting portion and c) the adapter bolt, on the other hand, said engagement element acting in the sense of a reinforcement of the consequential rotational force being able to be exerted on the base element.