Mounting set comprising a securing element with an associated securing pin which are configured to be mounted on a securing portion of a bicycle frame, the securing element being configured, furthermore, to mount a rear derailleur of a derailleur system on the support portion, the securing element comprising: - a first portion which has a through opening which is assigned to a mounting opening of the securing portion and, in that state of the securing element in which it is mounted on an inner side of the securing portion, is coaxial with respect to this securing portion; - a second portion which has a mounting opening, by means of which a base element of a rear derailleur can be mounted or is mounted on an outer side of the second portion; - an insertion bushing which is integral with the first portion or is attached to it, projects axially from the first portion, can be introduced or is introduced from the inner side of the securing portion into the mounting opening of the securing portion, into which the securing pin can be introduced or is introduced from an outer side of the securing portion, and which has a passage which adjoins the through opening; the insertion bushing with the securing pin which is inserted into it being able to be brought or being brought into a holding engagement which supports axial forces between the securing pin and the insertion sleeve, in order to hold the securing element and the securing pin on the securing portion; and the securing pin being configured with an internal thread, into which an external thread at a free end of a plug-in axle, guided through the through opening of the first portion, of a rear wheel axle arrangement of the bicycle can be screwed or is screwed, in order to fix the securing element with the securing pin on the securing portion; characterized in that at least one element of the insertion bushing and the securing pin is configured with at least one engagement formation (34; 60; 66; 68; 86) which is formed to establish an elastic snap-in holding connection or a bayonet-like holding locking action, which realises the holding engagement in a positively locking manner, together with at least one mating engagement element (32; 70), separate from the insertion bushing and the securing pin, or a mating engagement formation (52; 62) of the respective other element of the insertion bushing and the securing pin. the securing element comprising: - a first portion which has a through opening which is assigned to a mounting opening of the securing portion and, in that state of the securing element in which it is mounted on an inner side of the securing portion, is coaxial with respect to this securing portion; - a second portion which has a mounting opening, by means of which a base element of a rear derailleur can be mounted or is mounted on an outer side of the second portion; - an insertion bushing which is integral with the first portion or is attached to it, projects axially from the first portion, can be introduced or is introduced from the inner side of the securing portion into the mounting opening of the securing portion, into which the securing pin can be introduced or is introduced from an outer side of the securing portion, and which has a passage which adjoins the through opening; - a first portion which has a through opening which is assigned to a mounting opening of the securing portion and, in that state of the securing element in which it is mounted on an inner side of the securing portion, is coaxial with respect to this securing portion; - a second portion which has a mounting opening, by means of which a base element of a rear derailleur can be mounted or is mounted on an outer side of the second portion; - an insertion bushing which is integral with the first portion or is attached to it, projects axially from the first portion, can be introduced or is introduced from the inner side of the securing portion into the mounting opening of the securing portion, into which the securing pin can be introduced or is introduced from an outer side of the securing portion, and which has a passage which adjoins the through opening; the insertion bushing with the securing pin which is inserted into it being able to be brought or being brought into a holding engagement which supports axial forces between the securing pin and the insertion sleeve, in order to hold the securing element and the securing pin on the securing portion; and the securing pin being configured with an internal thread, into which an external thread at a free end of a plug-in axle, guided through the through opening of the first portion, of a rear wheel axle arrangement of the bicycle can be screwed or is screwed, in order to fix the securing element with the securing pin on the securing portion; characterized in that at least one element of the insertion bushing and the securing pin is configured with at least one engagement formation (34; 60; 66; 68; 86) which is formed to establish an elastic snap-in holding connection or a bayonet-like holding locking action, which realises the holding engagement in a positively locking manner, together with at least one mating engagement element (32; 70), separate from the insertion bushing and the securing pin, or a mating engagement formation (52; 62) of the respective other element of the insertion bushing and the securing pin.