The invention relates to the field of supporting interfaces, and particularly a supporting interface (30a, 30b) of this kind for an engine crankcase (90) and including a coupling part (50), a first plurality of bolts (80) and a plurality of pins (70). The coupling part (50) includes an outer surface (52) having a cavity (42) capable of receiving a support arm (20a, 20b), an inner surface (51) which can be mounted on an outer surface (93) of the engine crankcase (90), and a first plurality of openings (53) between the outer surface (52) and the inner surface (51) of the coupling part (50). The bolts (80) each include a threaded rod (82) received in one opening (53) of the first plurality of openings (53), and a head (81) capable of bearing on the outer surface (52) of the coupling part (50). Each pin (70) includes a threaded opening (71) in which the threaded rod (82) of one of the bolts (80) of the first plurality of bolts (80) is inserted through a first end of the pin (70), and a second widened end capable of bearing on an inner surface (92) of the engine crankcase (90). The invention also relates to a method for mounting such a supporting interface.