Tread (2) of a radial tire for a heavy vehicle. The tire alternatingly rolls in laden and unladen states on descent and ascent, respectively. Tread (2) has total width W.sub.T and comprises first median portion (21) having median width W.sub.c, where 0.2W.sub.T≤W.sub.c≤0.5W.sub.T. Tread (2) is axially delimited by second and third lateral portions (22, 23) having respective lateral widths (W.sub.S2, W.sub.S3) at least equal to 25% and at most equal to 40% of total width W.sub.T. Angle A.sub.51 of leading face (51) of every element in relief (31) of first median portion (21) is strictly greater than angle A.sub.61 of trailing face (61) of said element in relief (31). Angle (A.sub.52, A.sub.53) of leading face (52, 53) of every element in relief (32, 33) of each of the second and third lateral portions (22, 23) is strictly less than angle (A.sub.62, A.sub.63) of trailing face (62, 63) of said element in relief (32, 33).

A tyre comprising an adaptive tread, the adaptive tread comprising a plurality of surface sections, wherein each surface section can move without deformation relative to the other surface sections to form a tread pattern.

A tyre comprising an adaptive tread, the adaptive tread comprising a plurality of surface sections, wherein each surface section can move without deformation relative to the other surface sections to form a tread pattern.

A tire for an agricultural vehicle (1), and in particular the carcass reinforcement (4) thereof, for a tire running at low pressure on loose ground, is to reduce the compaction of the ground and to increase the traction capability by reducing the structural stiffness of the tire. According to the invention, the carcass reinforcement (4) is made up of a single carcass layer (41) having a mean thickness E at most equal to 2 mm and a breaking strength Fr, expressed in daN/cm, that satisfies the relationship:

Fr>=Fs=(Cs*Pmax*10.sup.−3)*((R.sup.2−((R+Rj)/2).sup.2)/2)/Rj, with Fs: reference threshold strength (in daN/cm) Cs: safety factor at least equal to 1, Pmax: recommended maximum inflation pressure (in kPa), R=D/2: outside radius of the tire (in mm), Rj=Dj/2: nominal radius of the rim (in mm).

A tire for an agricultural vehicle (1), and in particular the carcass reinforcement (4) thereof, for a tire running at low pressure on loose ground, is to reduce the compaction of the ground and to increase the traction capability by reducing the structural stiffness of the tire. According to the invention, the carcass reinforcement (4) is made up of a single carcass layer (41) having a mean thickness E at most equal to 2 mm and a breaking strength Fr, expressed in daN/cm, that satisfies the relationship:

Fr>=Fs=(Cs*Pmax*10.sup.−3)*((R.sup.2−((R+Rj)/2).sup.2)/2)/Rj, with Fs: reference threshold strength (in daN/cm) Cs: safety factor at least equal to 1, Pmax: recommended maximum inflation pressure (in kPa), R=D/2: outside radius of the tire (in mm), Rj=Dj/2: nominal radius of the rim (in mm).

A Tire tread with blocks for a heavy construction-plant vehicle, to improve the compromise between traction on muddy ground and lifetime in terms of wear on rough ground. A tread (1) has blocks (4), which are separated by cuts (3) and raised with respect to a bottom surface (5). Any block (4) have a contact face (41) having a polygonal shape of surface area SC, which is contained in a tread surface (2), lateral faces (42), and a base section (43) , which has a polygonal shape of surface area SB. The contact face (41) of any block (4) has a polygonal shape that is at least partially concave, wat least two consecutive sides (411, 412) that form between them an interior angle A1 of the polygonal shape that is greater than 180° and the surface area SC of the contact face (41) is at most equal to 0.9 times the surface area SB of the base section (43).

A Tire tread with blocks for a heavy construction-plant vehicle, to improve the compromise between traction on muddy ground and lifetime in terms of wear on rough ground. A tread (1) has blocks (4), which are separated by cuts (3) and raised with respect to a bottom surface (5). Any block (4) have a contact face (41) having a polygonal shape of surface area SC, which is contained in a tread surface (2), lateral faces (42), and a base section (43) , which has a polygonal shape of surface area SB. The contact face (41) of any block (4) has a polygonal shape that is at least partially concave, wat least two consecutive sides (411, 412) that form between them an interior angle A1 of the polygonal shape that is greater than 180° and the surface area SC of the contact face (41) is at most equal to 0.9 times the surface area SB of the base section (43).

A tire for running on rough terrain for which an intended tire rotational direction is specified. The tread portion is provided with blocks raised from a tread base portion. Each block has a first side wall surface comprising a radially outer portion extending substantially straight and radially inwardly, while inclining toward the toe side in the intended tire rotational direction, and a radially inner portion extending from the radially outer portion to the tread base portion while curving in an arc shape. The radially outer portion has a radial length of from 30% to 70% of a radial height of the block.

A tire for running on rough terrain for which an intended tire rotational direction is specified. The tread portion is provided with blocks raised from a tread base portion. Each block has a first side wall surface comprising a radially outer portion extending substantially straight and radially inwardly, while inclining toward the toe side in the intended tire rotational direction, and a radially inner portion extending from the radially outer portion to the tread base portion while curving in an arc shape. The radially outer portion has a radial length of from 30% to 70% of a radial height of the block.

A tire for running on rough terrain for which an intended tire rotational direction is specified, and which comprises a tread portion provided with crown blocks disposed on the tire equator. Each of the crown blocks comprises a V-shaped crown block main portion which bends convexly toward a circumferential direction opposite to the intended tire rotation direction, and only two crown fin portions projecting from the crown block main portion toward the above-said circumferential direction opposite to the intended tire rotation direction.