Tyre having a tread comprising a central portion astride an equatorial plane (X-X) and two shoulder portions (L2,L3), wherein: the shoulder portions (L1; L2) each have at least one row of lateral blocks (13;14); the central portion comprises a first and a second row (9;10) of central blocks having an elongate shape; each block of the first central row is substantially arranged axially side by side with a block of the second row such as to define a first substantially transverse drainage channel, substantially continuous, which crosses the central portion; said first substantially transverse drainage channel is defined between a first pair of blocks, formed by a block of the first row and a block of the second row arranged axially side by side, and the first circumferentially adjacent pair of blocks, formed in a similar way; each block of the first row is arranged according to an extension direction; each block of the second row extends according to an extension direction substantially aligned with the extension direction of the circumferentially preceding block of the first row such as to define an inclined and substantially continuous second drainage channel which crosses the central portion; said second drainage channel being defined between a second pair of blocks, formed by a block of the second row and the block of the first row which precedes the former in circumferential direction and is aligned thereto according to the substantially common extension direction, and the circumferentially adjacent second pair of blocks formed in a similar way; the tyre being charcterized in that: the central portion has a void-to-rubber ratio lower than 0,25; at least one side of a block of the first row lies in a plane substantially parallel to said common extension direction and is substantially aligned with at least another side of a block of the second row for downwardly delimiting the second drainage channel. the shoulder portions (L1; L2) each have at least one row of lateral blocks (13;14); the central portion comprises a first and a second row (9;10) of central blocks having an elongate shape; each block of the first central row is substantially arranged axially side by side with a block of the second row such as to define a first substantially transverse drainage channel, substantially continuous, which crosses the central portion; said first substantially transverse drainage channel is defined between a first pair of blocks, formed by a block of the first row and a block of the second row arranged axially side by side, and the first circumferentially adjacent pair of blocks, formed in a similar way; each block of the first row is arranged according to an extension direction; each block of the second row extends according to an extension direction substantially aligned with the extension direction of the circumferentially preceding block of the first row such as to define an inclined and substantially continuous second drainage channel which crosses the central portion; said second drainage channel being defined between a second pair of blocks, formed by a block of the second row and the block of the first row which precedes the former in circumferential direction and is aligned thereto according to the substantially common extension direction, and the circumferentially adjacent second pair of blocks formed in a similar way; the tyre being charcterized in that: the central portion has a void-to-rubber ratio lower than 0,25; at least one side of a block of the first row lies in a plane substantially parallel to said common extension direction and is substantially aligned with at least another side of a block of the second row for downwardly delimiting the second drainage channel. the central portion has a void-to-rubber ratio lower than 0,25; at least one side of a block of the first row lies in a plane substantially parallel to said common extension direction and is substantially aligned with at least another side of a block of the second row for downwardly delimiting the second drainage channel.