Winter tyre

A winter tyre, comprising a tread band wherein a plurality of blocks is defined, at least some of said blocks comprising at least one sipe extending from a top portion of the block towards a bottom portion of the block, wherein said at least one sipe defines two adjacent block portions in the block, each of said two block portions comprising a surface facing said at least one sipe, said surface comprising:

• a radially outer portion having a first profile which is substantially undulating;
• a radially inner portion having a second profile which is substantially undulating;
• and
• an intermediate portion arranged between said radially outer portion and said radially inner portion and having a third profile which is substantially rectilinear;
• wherein
• said intermediate portion defines a reference plane substantially coinciding with a radial plane of the tyre,
• said first profile and second profile are defined by a plurality of concave and convex portions arranged in an alternating sequence along a direction parallel to a longitudinal direction of said at least one sipe, and each of the concave and convex portions of the second profile comprises:
• a radially outer surface portion,
• a radially inner surface portion, and
• an intermediate surface portion arranged between said radially outer surface portion and said radially inner surface portion, wherein said intermediate surface portion is substantially parallel to said reference plane in any transversal section of the sipe,
• in any transversal section of the sipe, each intermediate surface portion of each concave and convex surface portion is substantially rectilinear, and
• at a crest of each concave and convex surface portion, the intermediate surface portion is spaced apart from said reference plane.