Tread for a pneumatic tyre comprising a sipe having a sipe extension (L) and a sipe depth (P) along a direction of wear (U), wherein said sipe has at least two sections (S1, S2) along said direction of wear (U) having respective differentiated conformations, such that an intersection profile (P1, P2) between the sipe and a surface (T1, T2) parallel to the contact surface of the tread is different for each of said at least two sections (S1, S2), wherein at least one surface section (S1) of said at least two sections (S1, S2) has a depth (PS) that is variable along said sipe extension (L), said two sections (S1, S2) being connected by a transition section (S3) defining a transition line (TL) between the respective sections (S1, S2), said variable depth (PS) of said surface section, presenting a maximum depth (PSMAX) and a minimum depth (PSMIN), and wherein the surface section (SI) has a twisted configuration.