Process for producing tyres provided with auxiliary components for vehicle wheels, comprising: a) forming, on a forming drum, a green tyre comprising a carcass structure comprising at least one carcass layer having opposite lateral edges associated with respective bead structures, a pair of sidewalls laterally applied on opposite sides of said carcass structure, a layer of impermeable elastomeric material applied at a radially inner position with respect to said carcass structure, b) arranging an expandable vulcanisation chamber; c) shaping, moulding and vulcanising the green tyre in a manner so as to obtain a finished tyre; d) making an auxiliary component adhere on a first radially inner surface portion of the tyre; wherein arranging an expandable vulcanisation chamber comprises: b1) covering the external surface of said expandable vulcanisation chamber with a first substantially cross-linkable polysiloxane composition A comprising A1) at least one reactive polysiloxane oil having OH groups, A2) at least one cross-linking agent comprising at least two functional groups capable of reacting with the reactive polysiloxane oil A1) b2) cross-linking said first substantially cross-linkable polysiloxane composition A on the expandable chamber; b3) repeating at least once the aforesaid operations b1) and b2), and wherein shaping, moulding and vulcanising the green tyre comprises: c1) selecting at least one green tyre every n green tyres, where n is an integer less than 60; c2) covering at least one second portion of the radially inner surface of said impermeable elastomeric material layer of said at least one selected green tyre with a second substantially non-cross-linkable polysiloxane composition B comprising B1) at least one non-reactive polysiloxane oil, wherein said second portion on the green tyre corresponds with a portion on the finished tyre substantially not superimposing said first portion. a) forming, on a forming drum, a green tyre comprising a carcass structure comprising at least one carcass layer having opposite lateral edges associated with respective bead structures, a pair of sidewalls laterally applied on opposite sides of said carcass structure, a layer of impermeable elastomeric material applied at a radially inner position with respect to said carcass structure, b) arranging an expandable vulcanisation chamber; c) shaping, moulding and vulcanising the green tyre in a manner so as to obtain a finished tyre; d) making an auxiliary component adhere on a first radially inner surface portion of the tyre; b1) covering the external surface of said expandable vulcanisation chamber with a first substantially cross-linkable polysiloxane composition A comprising A1) at least one reactive polysiloxane oil having OH groups, A2) at least one cross-linking agent comprising at least two functional groups capable of reacting with the reactive polysiloxane oil A1) b2) cross-linking said first substantially cross-linkable polysiloxane composition A on the expandable chamber; b3) repeating at least once the aforesaid operations b1) and b2), and wherein shaping, moulding and vulcanising the green tyre comprises: c1) selecting at least one green tyre every n green tyres, where n is an integer less than 60; c2) covering at least one second portion of the radially inner surface of said impermeable elastomeric material layer of said at least one selected green tyre with a second substantially non-cross-linkable polysiloxane composition B comprising B1) at least one non-reactive polysiloxane oil, wherein said second portion on the green tyre corresponds with a portion on the finished tyre substantially not superimposing said first portion.