Winter tyre

A tyre comprising a tread band, a tread surface radially outer to said tread band, at least one block defined on said tread band and at least one complex-type sipe obtained on said at least one block, said at least one complex-type sipe being open on said tread surface to define a longitudinal direction of development of said at least one complex-type sipe,

• wherein said at least one complex-type sipe separates said at least one block into:
• a first block portion comprising a first surface extended from said tread surface towards an inside of said tread band, and
• a second block portion comprising a second surface, extended from said tread surface towards the inside of said tread band, said second surface facing and being substantially parallel to said first surface,
• wherein:
• said first surface is extended continuously between at least a first longitudinal section having a first radial profile and at least a second longitudinal section, spaced from said first longitudinal section, having a second radial profile,
• said first radial profile comprises a first coupling portion between said first block portion and said second block portion, defining a first protrusion of said first surface and a first recess of said first surface radially inner with respect to said first protrusion,
• said second radial profile comprises a second coupling portion between said first block portion and said second block portion, defining a second recess of said first surface and a second protrusion of said first surface radially inner with respect to said second recess,
• said first coupling portion is extended between a first radially outer end, crossed by a first reference plane parallel to said longitudinal direction of said at least one complex-type sipe and to a radial direction of said tread band, and a second radially inner end, crossed by a second reference plane parallel to said first reference plane,
• said first protrusion is delimited by a first length of said first radial profile extended from said first end with a first inclination with respect to said radial direction, and by a second length of said first radial profile extended from said first length with a second inclination with respect to said radial direction of opposite sign to said first inclination,
• said first recess is defined on an opposite side to said first protrusion with respect to said first reference plane and is delimited by said second length of said first radial profile and by a third length of said first radial profile extended from said second length up to said second end and having a third inclination with respect to said radial direction of opposite sign to said second inclination,
• said second length of said first radial profile is longer than said first length of said first radial profile and longer than said third length of said first radial profile,
• said second length of said first radial profile is angled closer to said radial direction than to a direction perpendicular thereto, and
• said second reference plane is spaced from said first reference plane and is interposed between said first recess and said first reference plane.