Abstract: A tyre carcass building drum (1) having a longitudinal axis (3) and two half-drums (6) movable along the longitudinal axis (3) in opposite directions away from and towards a centre plane (4) of the drum (1), each one comprising a bead carrying device (16) defining a saddle and a turn-up device (41) designed to turn up a annular side portion (42) of a carcass ply around, and on the outside of a respective bead ring; the turn-up device (43) having an end portion arranged, at rest, along a peripheral annular portion (18) of the saddle (17) and shaped so as to define an extension of the curvilinear profile of the saddle (17); and thrust means (50) being provided to directly and independently exert an axial thrust and a radial thrust on the turn-up device (43). The invention also relates to an operating method of said drum.