Jockey wheel for a rear derailleur in a bicycle gear system and rear derailleur with such a jockey wheel

A rear derailleur for a bicycle derailleur gear system for guiding a chain that has at least one guide wheel, the guide wheel comprising:

• a derailleur cage movably attached to the derailleur;
• an annular wheel body supported by the derailleur cage, the wheel body having a central opening for rotation about a rotational axis of the guide wheel;
• a plurality of radially projecting gear teeth arranged on an outer circumferential surface of the wheel body, each of the gear teeth at or near a root circle of the gear teeth having a predetermined tooth width engageably receivable by the chain;
• a tooth gap arranged between adjacent gear teeth;
• and
• at least one chain guide segment with a greater width than that of at least one of the adjacent gear teeth, the at least one chain guide segment located on one or both of i) at least some of the tooth gaps at a tooth gap base and ii) on at least some of the gear teeth.