Mould (1; 100) for vulcanising tyres for vehicle wheels, comprising: - at least one sidewall plate on which a moulding surface is defined which is intended for contacting an axially external surface of a sidewall of a green tyre, - a removable insert arranged to be received in a seat which is made in said sidewall plate and open on said moulding surface, wherein said insert comprises a main body (11; 111) on which a base surface is defined which is intended for contacting a portion of said external surface of said sidewall of the green tyre, and - a retaining member for retaining said insert inside said seat, which comprises at least one locking element (21; 121) which is mounted on one out of said insert and said sidewall plate and comprises a first contact surface (22a; 103) for contacting the other out of said insert and said sidewall plate, and wherein said at least one locking element (21; 121) can be moved in an operating direction, which is incident with respect to an insertion direction of said insert into said seat, between a locking position, in which said insert is retained inside said seat, and a release position, in which said insert is free to leave said seat; wherein said insert comprises a rod (13; 113) which extends in said insertion direction, on the opposite side to said base surface, and said first contact surface (22a; 103) engages said insert at said rod (13; 113) in order to retain said insert in said seat: and wherein - a first shoulder is defined on said rod, which shoulder is oriented so as to diverge away from said main body, inclined with respect to a longitudinal axis of said rod by an angle of between 10° and 70°, and positioned so as to contact said first contact surface when said locking element is in the locking position; or - said locking element is fixed to said sidewall plate and the first contact surface is inclined with respect to said operating direction by an angle of between 15° and 45°, contacting said insert and moving said insert in said insertion direction inside said seat further to the movement of said locking element in said operating direction. - at least one sidewall plate on which a moulding surface is defined which is intended for contacting an axially external surface of a sidewall of a green tyre, - a removable insert arranged to be received in a seat which is made in said sidewall plate and open on said moulding surface, wherein said insert comprises a main body (11; 111) on which a base surface is defined which is intended for contacting a portion of said external surface of said sidewall of the green tyre, and - a retaining member for retaining said insert inside said seat, which comprises at least one locking element (21; 121) which is mounted on one out of said insert and said sidewall plate and comprises a first contact surface (22a; 103) for contacting the other out of said insert and said sidewall plate, and wherein said at least one locking element (21; 121) can be moved in an operating direction, which is incident with respect to an insertion direction of said insert into said seat, between a locking position, in which said insert is retained inside said seat, and a release position, in which said insert is free to leave said seat; wherein said insert comprises a rod (13; 113) which extends in said insertion direction, on the opposite side to said base surface, and said first contact surface (22a; 103) engages said insert at said rod (13; 113) in order to retain said insert in said seat: and wherein - a first shoulder is defined on said rod, which shoulder is oriented so as to diverge away from said main body, inclined with respect to a longitudinal axis of said rod by an angle of between 10° and 70°, and positioned so as to contact said first contact surface when said locking element is in the locking position; or - said locking element is fixed to said sidewall plate and the first contact surface is inclined with respect to said operating direction by an angle of between 15° and 45°, contacting said insert and moving said insert in said insertion direction inside said seat further to the movement of said locking element in said operating direction.