The present invention relates to a polyester tire cord made of polyester yarn and having a 5% LASE of 1.2 g/d or more as measured according to ASTM D885 at 80° C., a 5% LASE of 1.0 g/d or more as measured according to ASTM D885 at 120° C., and a toughness retention rate of 65% or more at 80° C. and 120° C. The tire cord of the present invention has a modulus comparable to that of rayon even in a high-temperature environment at 120° C. or higher, and has excellent dimensional stability and heat resistance, and thus it can be advantageously applied to a high-performance tire.

Disclosed is a pneumatic radial tire for a passenger car having ultra fine steel cords for a carcass ply in which adhesive force between a carcass ply layer and a side wall or a rim flange rubber adjacent to a turn up portion on an outside and a stiffness of the rim flange rubber are larger than a bending stiffness of the carcass ply layer so as to improve durability of a bead part while reducing poor air inletting generated at a carcass turn up portion.

OD is defined by an outer diameter of the pneumatic tire, RW is defined by a rim width of a rim wheel assembled to the pneumatic tire, SW is defined by a tire width of the pneumatic tire, and RD is defined by a rim diameter of the pneumatic tire, the OD is 350 mm or more and 600 mm or less, the relation of 0.78≤RW/SW≤0.99; and the relation of 0.56≤RD/OD≤0.75 are satisfied.

Pneumatic vehicle tyre comprising a carcass (3), wherein the carcass (3) has two carcass plies (31, 32), wherein each carcass ply (31, 32) has reinforcements which are arranged inside the carcass ply (31, 32) substantially parallel to each other. The problem addressed by the invention is to provide a pneumatic vehicle tyre which likewise creates a high quality impression of sufficient robustness to a viewer and, in the process, is cheaper to produce and has a reduced rolling resistance. The invention is characterised in that the product EF1 of the average modulus of elasticity of the reinforcements, as measured with an extension of 2%, of the first carcass ply (31) and the thread density of the reinforcements of the first carcass ply (31), and the product EF2 of the average modulus of elasticity of the reinforcements of the second carcass ply (32) and the thread density of reinforcements of the second carcass ply (32), satisfy the relationship EF1>EF2.

A tire design for a heavy-duty vehicle of construction plant type has a crown reinforcement (40) radially on the inside of a tread (10) and radially on the outside of a carcass reinforcement (70). The carcass reinforcement (70) has at least two carcass layers (50, 60) having metal reinforcers coated in an elastomer compound. The carcass layers (50, 60) have respective stiffnesses per unit width R1, R2. Metal reinforcers of a first carcass layer (50) form, with the circumferential direction (XX′), an angle A1, and those of the second carcass layer form an angle A2, such that the angles A1 and A2, and the stiffnesses R1 and R2, simultaneously satisfy the following three relationships: R1*sin 2(2*A1)+R2*sin 2(2*A2)≥(R1+R2)*) sin 2(30°), and ∥A1|-|A2∥<10°, and 0.7≤R1/R2≤1.3. The metal reinforcers have a critical compression buckling deformation DF at least equal to 2.5% and a compression elastic modulus MC at least equal to 10 GPa.

The present invention discloses a preparation method of polyester cord fabric with low denier and high modulus, including steps of: spinning, reducing melt discharge volume for extruding yarn with denier of 500-1000 D; using high-speed motor and heat roller, spinning speed of 6000-6500 m/min to produce raw yarn; performing initial and repeat twisting of raw yarn by straight twisting machine; performing weaving of twisted yarn using Dornier air-jet loom to produce cord fabric, when weaving and reeding-in, using two into a reed way, adding creel roller bearing and creel single spindle tension control belt to improve uniformity; performing dipping of cord fabric using two-bath dipping, adjusting temperature to 250-260 degrees Celsius, tension to 0.3-2.9 daN/each yarn of key area, running speed of yarn to 55-70 m/min. The polyester cord fabric with low denier and high modulus can reduce rolling resistance and fuel consumption, and improve performance.

Provided is a pneumatic tire enabling improvement of side cut resistance and suppression of increase in mass. A pneumatic tire 1 includes: a tread portion 2; a pair of sidewall portions 3; a pair of bead portions 4 having respective bead cores 5 embedded therein; and a toroidal carcass 6 disposed between the pair of bead portions 4. The carcass 6 includes a first ply 11 extending on and between the pair of bead portions 4, and a second ply 12 disposed, in the tread portion 2, outward of the first ply 11 in a tire radial direction and extending on and between the pair of bead portions 4. The first ply 11 is formed as a layer of first cords. The second ply 12 is formed as a layer of second cords. A thickness of each second cord is 1.1 to 2.0 times a thickness of each first cord.

In a pneumatic tire, a carcass layer is between bead portions, a bead core is in each bead portion, a reinforcement layer is on an outer side of the carcass layer, and a tread rubber layer is on the outer side of the reinforcement layer. A pair of first boundary lines passes through an intersection of an extension of a side arc forming a tread profile and an extension of a shoulder arc and orthogonal to a tire inner surface, a pair of second boundary lines passes through a rim check line and orthogonal to the tire inner surface, first to third regions are defined which have cross sectional areas of SA, SB, and SC, respectively, and the first to third regions respectively have lengths of a, b, and c along the tire inner surface such that 7.5≤SA/a≤11.5 and 2.0≤SB/b≤6.0 are satisfied.

In a pneumatic tire, at least one carcass layer mounted between a pair of bead portions is formed from a carcass cord formed of an organic fiber cord having filament bundles of organic fibers intertwined together, a fineness based on corrected mass of the carcass cord is from 4000 dtex to 8000 dtex, an intermediate elongation of the carcass cord at a sidewall portion under 1.0 cN/dtex load is from 3.3% to 4.2%, and a ratio G/R of an interlayer rubber gauge G between a body portion and a folded back portion to a cord diameter R of the carcass cord, at a contact region where the body portion and the folded back portion are in contact in the carcass layer, is from 0.50 to 0.60.

To provide a tire that is not only improved in durability, steering stability, and low rolling resistance in high-speed driving but also excellent in tire productivity. A tire including a pair of bead cores (11), a carcass including at least one carcass ply (12) extending between the pair of bead cores (11), a belt (13) including at least one belt layer placed outward in a tire radial direction of the carcass, and at least one belt reinforcement layer (14) placed outward in a tire radial direction of the belt (13), in which a reinforcement cord of at least one of the carcass ply (12) and the belt reinforcement layer (14) includes a cord using a polyamide multifilament including a polycondensate of a dicarboxylic acid including an aromatic dicarboxylic acid with a diamine.