The present invention provides a pneumatic tire by which workability when molding a tire and tire durability performance can be enhanced without increasing tire weight when providing a reinforcing layer formed by aligning a plurality of monofilament steel wires and embedding this plurality of monofilament steel wires in rubber. The pneumatic tire of the present invention includes a reinforcing layer formed by aligning a plurality of monofilament steel wires and embedding said monofilament steel wires in rubber. Each of the monofilament steel wires is provided with twisting around an axis thereof, and a wire surface twisting angle with respect to an axial direction of the monofilament steel wires is not less than 1.

Two crossed tire working layers (41, 42), comprise mutually parallel reinforcing elements forming, with the circumferential direction (XX) of the tire, an angle at least equal to 20 and at most equal to 50. The reinforcing elements are made up of individual metal threads or monofilaments having a cross section at least equal to 0.20 mm and at most equal to 0.5 mm. The tire also comprises major grooves of a depth D at least equal to 5 mm and of a width W at least equal to 1 mm, axially exterior major grooves (26) opening inwardly into a circumferential groove (24) comprising at least one bridge of rubber (27) connecting the two main faces of the groove, the at least one bridge of rubber having a length LB at least equal to W and a height h at least equal to half the depth D of the groove.

Crown of a tire for a heavy vehicle of construction plant type is desensitized to attacks. The tire includes a tread (2) having a degree of surface siping TL, expressed in m/m.sup.2, equal to the ratio between the cumulative length L.sub.D of the cuts (21) and the area A of the radially outer surface (23) of the tread (2), and a protective reinforcement (4) having at least two protective layers (41, 42) that are formed of elastic metallic reinforcers and have a maximum breaking strength R.sub.max, expressed in daN/m, such that the degree of surface siping TL of the tread (2) is at least equal to 3 m/m.sup.2 and a coupling ratio C, equal to the ratio between the maximum breaking strength R.sub.max and the degree of surface siping TL, is at least equal to 30000 daN.

Technique to increase the endurance of tires comprising two crossed working layers (41, 42), comprising mutually parallel reinforcing elements that form, with the circumferential direction (XX) of the tire, an angle which is at least equal to 20 and at most equal to 50. The reinforcing elements are made up of individual metal threads or monofilaments having a cross section which is at least equal to 0.20 mm and at most equal to 0.5 mm. The tire also comprises axially exterior sipes (24) having a mean width W at most equal to 1 mm, of a depth D at least equal to 5 mm and spaced apart, in the circumferential direction (XX), by a circumferential spacing P at least equal to 4 mm, and axially exterior grooves (25) having a mean width W at least equal to 1 mm, of a depth D at most equal to 5 mm.

Technique to increase the endurance of tires comprising two working layers (41, 42), comprising mutually parallel reinforcing elements (411, 421) each forming, with the circumferential direction (XX) of the tire, an oriented angle (A1, A2) the absolute value of which is at least equal to 20 and at most equal to 50, such that these respective angles are of opposite sign. The reinforcing elements of each ply are made up of individual metal threads or monofilaments having a cross section the smallest dimension of which is at least equal to 0.20 mm and at most equal to 0.5 mm. The tire also comprises axially exterior major grooves (24) in the tread (2). The mean linear profile L of the axially exterior major grooves (24) of a width W at least equal to 1 mm and of a depth D at least equal to 5 mm forms, with the circumferential direction (XX), an angle C belonging to the interval [min(A1,A2)+100, max(A1, A2)+80].

Technique to increase the endurance of tires comprising two crossed working layers (41, 42), comprising mutually parallel reinforcing elements forming, with the circumferential direction (XX) of the tire, an angle which is at least equal to 20 and at most equal to 50. The reinforcing elements are made up of individual metal threads or monofilaments having a cross section which is at least equal to 0.20 mm and at most equal to 0.5 mm. The tire also comprises grooves comprising a radially inferior zone Z1 having a radial height h1 equal to D/3, and a radially superior zone Z2 having a radial height h2 equal to 2D/3. These grooves have a mean width W at least equal to 1 mm and a depth D at least equal to 5 mm, and a maximum width W1 of zone 1, at least equal to 2 mm and a width of zone 2 at most equal to 1 mm.

A pneumatic tire comprises: a carcass layer, a belt layer, and a tread rubber. The belt layer is formed by laminating a pair of cross belts having a belt angle of not less than 10 and not more than 45 in absolute terms and of mutually opposite signs, and a circumferential reinforcing layer having a belt angle within a range of 5 with respect to the tire circumferential direction. A distance (Gcc) from a tread profile to a tire inner circumference surface along a tire equatorial plane, a distance (Gsh) from a tread end to the tire inner circumference surface, and a distance (Ge) from the tread profile to the tire inner circumference surface at an end portion on the outer side of the circumferential reinforcing layer in the tire width direction have relationships satisfying 1.10Gsh/Gcc and 1.00Ge/Gcc1.10.

The tire includes a crown reinforcement which is formed of three working crown layers of reinforcing elements. The reinforcing elements of the two radially outermost working layers are crossed from one layer to the other, making with the circumferential direction angles of between 20 and 45 the circumferential direction, of the reinforcing elements of the radially innermost working layer being between 15 and 20. The reinforcing elements of the two radially innermost working layers are oriented in the same direction with respect to the circumferential direction. The difference between the angles of the reinforcing elements of the radially innermost working layers is greater than 10. The widths of the two radially outermost working layers are greater than the 0.7 times the width of the tread, and the width of the radially innermost working layer is strictly less than 0.7 times the width of the tread.

The steel wire of diameter d expressed in mm has a completely ferritic, pearlitic or ferritic-pearlitic microstructure and a weight content of carbon C such that 0.05%C<0.4%, a weight content of chromium Cr such that Cr<12% and a maximum tensile strength R, expressed in MPa, such that R175+930.C600.In(d) and R1500 MPa.

A tire for a heavy construction-type vehicle includes a tread, a radial carcass reinforcement, and a crown reinforcement. The crown reinforcement includes a working reinforcement and a hoop reinforcement. The working reinforcement includes two working layers, each of which includes inelastic metallic reinforcers that are crossed from one layer to a next layer and that make an angle in a range of from 15 to 40 with respect to a circumferential direction. The hoop reinforcement, which is a ply that is wound circumferentially to form a radial stack of at least two hooping layers, includes circumferential elastic metallic reinforcers that make an angle equal to at most 2.5 with respect to the circumferential direction. The hoop reinforcement is radially positioned between the working layers, and the circumferential metallic reinforcers of the hoop reinforcement have a force at break equal to at least 800 daN.