Tyre having a tread comprising a central annular portion astride an equatorial plane (X-X) and two shoulder annular portions (L2, L3), located on axially opposite sides with respect to the central annular portion, the central annular portion being separated from each shoulder annular portion by a respective first circumferential groove (3, 4), wherein the central annular portion comprises a plurality of blocks (20, 21), arranged in at least one circumferential row comprised between two circumferential grooves (3, 4, 5, 6, 7), and at least one sipe adapted to separate two circumferentially consecutive blocks (20, 21); each block being circumferentially delimited, by means of two consecutive sipes, by two opposite walls extending with a substantially transverse course with respect to the equatorial plane (X-X) of the tyre and with a substantially radial course from the bottom of the sipe to the radially outermost surface of the block (20, 21); on at least one of the opposite transverse walls of a block (20, 21) being present at least one first deformation (302; 303) adapted to define together with at least one adjacent block (20; 21) first portions of mutual constraint; the said at least one first deformation (302, 303) present on a first block (20, 21) defining a first constraint with a corresponding first deformation (302, 303) present on the facing wall of a second block (20, 21) circumferentially adjacent to the first block (20, 21); said first constraint acting at least in a circumferential direction; - on at least one of the opposite transverse walls of a block (20, 21) at least one second deformation is present which is adapted to define in the adjacent blocks (20, 21) further respective portions of mutual constraint; - said second deformation present on a first block (20, 21) defines a second constraint with a corresponding second deformation present on the facing wall of a second block (20, 21) circumferentially adjacent to the said first block (20, 21), said second constraint acting at least in a radial direction; - said second deformation extends at least on the said first deformation (302; 303) so that the first and second deformations are at the same wall portion of the block; characterized in that - said second deformation extends axially so as to follow a course located at different radial depths of the sipe; - said second deformation extends axially in a range comprised between about 30% and 80% of the transverse wall of the block. - on at least one of the opposite transverse walls of a block (20, 21) at least one second deformation is present which is adapted to define in the adjacent blocks (20, 21) further respective portions of mutual constraint; - said second deformation present on a first block (20, 21) defines a second constraint with a corresponding second deformation present on the facing wall of a second block (20, 21) circumferentially adjacent to the said first block (20, 21), said second constraint acting at least in a radial direction; - said second deformation extends at least on the said first deformation (302; 303) so that the first and second deformations are at the same wall portion of the block; - said second deformation extends axially so as to follow a course located at different radial depths of the sipe; - said second deformation extends axially in a range comprised between about 30% and 80% of the transverse wall of the block.