MOUNTED ASSEMBLY INCLUDING A PNEUMATIC TIRE

Abstract

The fitted assembly (10) comprises a tire (11) for a passenger vehicle comprising a working layer (26) which is axially the least wide, the working layer (26) which is axially the least wide having an axial width T2 expressed in mm. The fitted assembly (10) comprises a fitting support (100) comprising a rim (200) with a rim width A according to the manual of the ETRTO 2019 standard, and expressed in mm. The tire (11) has a load rating LI such that LI≥LI′+1, LI′ being the load rating of an EXTRA LOAD tire with the same size according to the manual of the ETRTO 2019 standard. The ratio T2/A is such that T2/A≤1.00.

Claims

1.-15. (canceled)

16. A fitted assembly (10) comprising: a tire (11) for a passenger vehicle comprising a crown (12), two beads (32), two sidewalls (30) which each connect each bead (32) to the crown (12), and a carcass reinforcement (34) which is anchored in each bead (32), the crown (12) comprising a crown reinforcement (16) and a tread (14), the carcass reinforcement (34) extending into each sidewall (30) and into the crown (12) radially into an interior of the crown reinforcement (16), the crown reinforcement (16) being arranged radially between the tread (14) and the carcass reinforcement (34), and comprising a working reinforcement (20) comprising at least one working layer (26) which is axially least wide, the working layer (26) which is axially least wide having an axial width T2 expressed in mm; and a fitting support (100) comprising a rim (200) with a rim width A according to standard ETRTO 2019 and expressed in mm, wherein the tire (11) has a load rating LI such that LI≥LI′+1, where LI′ is a load rating of an EXTRA LOAD tire with a same size according to standard ETRTO 2019, and wherein a ratio T2/A is such that T2/A≤1.00.

17. The fitted assembly (10) according to claim 16, wherein LI′+1≤LI≤LI′+4.

18. The fitted assembly (10) according to claim 16, wherein 0.85≤T2/A.

19. The fitted assembly (10) according to claim 18, wherein 0.90≤T2/A.

20. The fitted assembly (10) according to claim 16, wherein the tire (11) has a nominal cross-sectional width SW such that T2≥SW−75 and T2≤SW−27.

21. The fitted assembly (10) according to claim 16, wherein the rim (200) is selected from: a rim with a rim width code equal to a width code of a measurement rim for a size of the tire, and defined according to standard ETRTO 2019; a rim with a rim width code equal to a width code of a measurement rim for a size of the tire reduced by 0.5; and a rim with a rim width code equal to a width code of a measurement rim for a size of the tire increased by 0.5.

22. The fitted assembly (10) according to claim 16, wherein the tire (11) has a nominal cross-sectional width SW ranging from 205 to 315, a nominal aspect ratio ranging from 25 to 55, a nominal rim diameter ranging from 17 to 23, and the load rating LI ranging from 98 to 116.

23. The fitted assembly (10) according to claim 16, wherein 0.82≤H/LI≤0.98, H being a sidewall height defined by H=SW×AR/100, where SW is a nominal section width and AR is a nominal aspect ratio of the tire.

24. The fitted assembly (10) according to claim 16, wherein the tire (11) has a size and load rating LI selected from the following sizes and load ratings: 225/55R18 105, 225/55ZR18 105, 205/55R19 100, 205/55ZR19 100, 235/45R21 104, 235/45ZR21 104, 285/45R22 116, 285/45ZR22 116, 205/40R17 88, 205/40ZR17 88, 245/40R19 101, 245/40ZR19 101, 255/40R20 104, 255/40ZR20 104, 245/40R21 103, 245/40ZR21 103, 255/40R21 105, 255/40ZR21 105, 265/40R21 108, 265/40ZR21 108, 255/40R22 106, 255/40ZR22 106, 255/35R18 98, 255/35ZR18 98, 245/35R20 98, 245/35ZR20 98, 265/35R20 102, 265/35ZR20 102, 245/35R21 99, 245/35ZR21 99, 255/35R21 101, 255/35ZR21 101, 265/35R21 103, 265/35ZR21 103, 275/35R21 105, 275/35ZR21 105, 285/35R21 108, 285/35ZR21 108, 295/35R22 111, 295/35ZR22 111, 275/35R23 108, 275/35ZR23 108, 285/30R21 103, 285/30ZR21 103, 315/30R21 109, 315/30ZR21 109, 325/30R21 111, 325/30ZR21 111, 315/30R23 111, and 315/30ZR23 111.

25. The fitted assembly (10) according to claim 16, wherein the tire (11) is inflated to a pressure ranging from 200 to 350 kPa.

26. The fitted assembly (10) according to claim 16, wherein the working reinforcement (20) comprises a radially interior working layer (24) and a radially exterior working layer (26) arranged radially on an exterior of the radially interior working layer (24).

27. The fitted assembly (10) according to claim 16, wherein the working layer which is axially least wide (26) or each working layer (24, 26) is delimited axially by two axial edges (241, 242, 261, 262) of the working layer (24, 26) and comprises working thread reinforcement elements extending axially from one axial edge to an other axial edge of the working layer (24, 26) substantially parallel to one another.

28. The fitted assembly (10) according to claim 27, wherein each working thread reinforcement element extends in a main direction which, together with a circumferential direction (X) of the tire (11), forms an angle, in absolute value, which is strictly greater than 10°.

29. The fitted assembly (10) according to claim 16, wherein the carcass reinforcement (34) comprises at least one layer of carcass (36, 37), the or each layer of carcass (36, 37) being delimited axially by two axial edges (361, 362, 371, 372) of the or each layer of carcass (36, 37), and comprises carcass textile thread reinforcement elements (360, 370) extending axially from one axial edge to an other axial edge of the or each layer of carcass (36, 37) in a main direction forming an angle ranging, in absolute value, from 80° to 90° with a circumferential direction (X) of the tire (11).

30. The fitted assembly (10) according to claim 16, wherein the carcass reinforcement comprises a single carcass layer, the tire having a sidewall height H defined by H=SW×AR/100 with SW being a nominal section width and AR a nominal aspect ratio of the tire and such that H<95 and that 0.82≤H/LI≤0.92.

31. The fitted assembly (10) according to claim 30, wherein the single carcass layer forms a winding around a circumferential reinforcing element of each bead such that an axially inner portion of the single carcass layer is arranged axially on an inside of an axially outer portion of the single carcass layer and such that each axial end of the single carcass layer is arranged radially on an outside of each circumferential reinforcing element.

32. The fitted assembly (10) according to claim 30, wherein the single carcass layer has a portion arranged axially between two circumferential reinforcing elements of each bead and each axial end of the single carcass layer is arranged radially on an inside of each radially outer end of each circumferential reinforcing element of each bead.

33. The fitted assembly (10) according to claim 16, wherein the carcass reinforcement comprises first and second carcass layers, the tire having a sidewall height H defined by H=SW×AR/100 with SW being a nominal section width and AR a nominal aspect ratio of the tire and such that H≥95 and that 0.88≤H/LI≤0.98.

34. The fitted assembly (10) according to claim 16, wherein the crown reinforcement (16) comprises a hoop reinforcement (22) which is delimited axially by two axial edges (281, 282) of the hoop reinforcement, and comprising at least one wrapping thread reinforcement element wound circumferentially, helically, such as to extend axially between the axial edges (281, 282) of the hoop reinforcement (22).

35. A passenger vehicle comprising at least one fitted assembly (10) according to claim 16.

Description

[0118] The invention will be better understood by reading the following description, provided purely by way of non-limiting example, with reference to the drawings in which:

[0119] FIG. 1 is a view, on a meridian cross-sectional plane, of an assembly fitted according to a first embodiment of the invention;

[0120] FIG. 2 is a view, on a meridian cross-sectional plane, of the tire of the fitted assembly of FIG. 1;

[0121] FIG. 3 is a view in cross-section according to the plane III-III′ of FIG. 2 illustrating the carcass reinforcement of the tire of FIG. 1;

[0122] FIGS. 4 and 5 are views similar respectively to FIGS. 2 and 3 of a tire for a fitted assembly according to a second embodiment of the invention; and

[0123] FIG. 6 is a view analogous to that of FIG. 1 comparing the camber of a fitted assembly according to the prior art and that of the fitted assembly of FIG. 1.

[0124] In the figures, X, Y, Z represents a reference corresponding to the habitual directions, respectively axial (Y), radial (Z) and circumferential (X), of a tire or of a fitted assembly.

[0125] In the following description the measurements made are carried out on a tire which is unloaded and not inflated, or on a cross-section of a tire on a meridian plane.

Fitted Assembly According to a First Embodiment

[0126] FIG. 1 represents a fitted assembly according to the invention designated by the general reference 10. The fitted assembly 10 comprises a tire 11 and a fitting support 100 comprising a rim 200. The tire 11 is in this case inflated to a pressure ranging from 200 to 350 kPa, preferably from 250 to 330 kPa, and in this case equal to 270 kPa.

[0127] The tire 11 has a substantially toric form around an axis of revolution R which is substantially parallel to the axial direction Y. The tire is designed for a passenger vehicle. In the different figures, the tire 11 is represented in the new state, i.e. not yet having travelled.

[0128] The tire 11 comprises two sidewalls 30 bearing marking indicating the size of the tire 11, as well as a speed rating and speed code. In this case, the tire 11 has a nominal cross-sectional width SW ranging from 205 to 315, preferably 225 to 315, more preferably from 245 to 315, and in this case equal to 255. The tire 11 also has a nominal aspect ratio AR ranging from 25 to 55, preferably ranging from 30 to 45, and in this case equal to 35. The tire 11 has a nominal rim diameter ranging from 17 to 23 and preferably ranging from 18 to 23, and in this case equal to 18. The tire 11 thus has a height of sidewall H defined by SW×AR/100=89<95.

[0129] According to the invention, the marking also comprises a load rating LI ranging from 98 to 116, such that LI≥LI′+1, where LI′ is the load rating of an EXTRA LOAD tire with the same size according to the manual of the ETRTO 2019 standard. Preferably, LI′+1≤LI≤LI′+4, and even LI′+2≤LI≤LI′+4.

[0130] A tire with a size 255/35R18 in its EXTRA LOAD version has a load rating equal to 94, as indicated on page 36 of the part Passenger Car Tyres—Tyres with Metric Designation of the manual of the ETRTO 2019 standard. Thus, the load rating LI of the tire 11 is such that LI≥95, preferably 95≤LI≤98 and even 96≤LI≤98 and in this case LI=98. This load rating equal to 98 corresponds well to the load rating of a HIGH LOAD CAPACITY tire with a size of 255/35R18, as indicated in the ETRTO 2021 manual. Thus, the tire 11 is of the HIGH LOAD CAPACITY type.

[0131] The tire 11 is such that 0.82≤H/LI≤0.98 and preferably 0.82≤H/LI≤0.92 and in this case H/LI=0.91.

[0132] For a size of this type, the manual of the ETRTO 2019 standard indicates on page 36 of the part Passenger Car Tyres—Tyres with Metric Designation, a measurement rim with a rim width code equal to 9. The rim 200 of the fitted assembly 10 is thus selected from amongst: [0133] a rim with a rim width code equal to the width code of the measurement rim for the size of the tire, and defined according to the manual of the ETRTO 2019 standard; and [0134] a rim with a rim width code equal to the width code of the measurement rim for the size of the tire reduced by 0.5; and [0135] a rim with a rim width code equal to the width code of the measurement rim for the size of the tire increased by 0.5.

[0136] In this case, the rim 200 of the fitted assembly 10 is the rim with a rim width code equal to the width code of the measurement rim for the size of the tire reduced by 0.5, and thus in this case equal to 8.5. The rim 200 has a profile of the type “J” and a rim width A according to the manual of the ETRTO 2019 standard. In this case, since the profile of the rim 200 is of the type 8.5 J, its rim width A expressed in mm is equal to 215.90 mm.

[0137] With reference to FIG. 2, the tire 11 comprises a crown 12 comprising a tread 14 which is designed to come into contact with a ground during running, and a crown reinforcement 16 extending in the crown 12 in the circumferential direction X. The tire 11 also comprises a layer 18 of sealing against an inflation gas, which layer is designed to delimit a closed inner cavity together with the fitting support 100 of the tire 11, once the tire 11 has been fitted on the fitting support 100.

[0138] The crown reinforcement 16 comprises a working reinforcement 20 and a hoop reinforcement 22. The working reinforcement 16 comprises at least one working layer, and in this case comprises two working layers comprising a radially interior working layer 24 which is arranged radially in the interior of a radially exterior working layer 26. From out of the two, radially interior 24 and radially exterior layers 26, the layer which is axially the least wide is the radially exterior layer 26.

[0139] The hoop reinforcement 22 comprises at least one wrapping layer, and in this case comprises one wrapping layer 28.

[0140] The crown reinforcement 16 is surmounted radially by the tread 14. In this case the hoop reinforcement 22, in this case the wrapping layer 28, is arranged radially on the exterior of the working reinforcement 20, and is thus radially interposed between the working reinforcement 20 and the tread 14.

[0141] The two sidewalls 30 prolong the crown 12 radially towards the interior. The tire 11 also comprises two beads 32 radially in the interior of the sidewalls 30. Each sidewall 30 connects each bead 32 to the crown 12.

[0142] The tire 11 comprises a carcass reinforcement 34 which is anchored in each bead 32, and in this case forms a winding around a circumferential reinforcement element 33, in this case a rod. The carcass reinforcement 34 extends radially into each side wall 30, and axially into the crown 12, radially in the interior of the crown reinforcement 16. The crown reinforcement 16 is arranged radially between the tread 14 and the carcass reinforcement 34. The carcass reinforcement 34 comprises at least one carcass layer 36, and in this case a single carcass layer 36.

[0143] The hoop reinforcement 22, in this case the wrapping layer 28, is delimited axially by two axial edges 281, 282, and comprises one or a plurality of wrapping thread reinforcement elements wound circumferentially, helically, between each axial edge 281, 282 in a main direction which, together with the circumferential direction X of the tire 10, forms an angle AF, in absolute value, of 10° or less, preferably 7° or less, and more preferably 5° or less. In this case, AF=−5°.

[0144] Each radially interior 24 and radially exterior 26 working layer is delimited axially by two axial edges, respectively 241, 242, 261, 262, of each working layer 24, 26. The radially interior working layer 24 has an axial width T1=223.00 mm, and the radially exterior working layer 26 has an axial width T2=209.00 mm, making the radially exterior working layer 26 the working layer which is axially the least wide.

[0145] It will be noted that SW=255 and T2=209 satisfy the following equations: T2≥SW−75, preferably T2≥SW−70 and T2≥SW−27, preferably T2≥SW−30.

[0146] As illustrated in FIG. 1, the fitted assembly 10 is such that the tire 11 has sidewalls which are rectified radially. In fact, the ratio T2/A is such that 0.85≤T2/A≤1.00, preferably 0.90≤T2/A≤1.00, and more preferably 0.93≤T2/A≤0.97 and in this case T2/A=0.97.

[0147] Each working layer 24, 26 comprises working thread reinforcement elements extending axially from one axial edge 241, 261 to the other axial edge 242, 262 of each working layer 24, 26, substantially parallel to one another in main directions which form together with the circumferential direction X of the tire 10 angles respectively AT1 and AT2 with opposite orientations, which, in absolute value, are strictly greater than 10°, preferably ranging from 15° to 50°, and more preferably ranging from 20° to 35°. In this case, AT1=−26° and AT2=+26°.

[0148] The single layer of carcass 36 is delimited axially by two axial edges, respectively 361, 362, and comprises carcass textile thread reinforcement elements, respectively 360, extending axially from one axial edge 361 to the other axial edge 362 in a main direction D3 forming with the circumferential direction X of the tire 10 an angle AC, in absolute value, ranging from 80° to 90°, and in this case AC=+90°.

[0149] The single layer of carcass 36 forms a winding around each circumferential reinforcement element 33 of each bead 32, such that an axially interior portion 3611, 3621 of the first layer of carcass 36 is arranged axially in the interior of an axially exterior portion 3612, 3622 of the first layer of carcass 36, and such that each axial end 361, 362 of the first layer of carcass 36 is arranged radially on the exterior of each circumferential reinforcement element 33.

[0150] Each axial end 361, 362 of the single layer of carcass 36 is arranged radially in the interior of the equator E of the tire. More specifically, each axial end 361, 362 of the first layer of carcass 36 is arranged at a radial distance RNC of 30 mm or less from a radially interior end 331 of each circumferential reinforcement element 33 of each bead 32. In this case, RNC=23 mm.

[0151] Each working layer, 24, 26, of wrapping 28 and carcass 36, comprises a die for calendering thread reinforcement elements of the corresponding layer. Preferably, the calendering die is made of polymer, and more preferably elastomer, such as those conventionally used in the domain of tires.

[0152] Each wrapping thread reinforcement element conventionally comprises two multifilament plies, each multifilament ply being constituted by a thread of aliphatic polyamide monofilaments, in this case nylon, with a yarn count equal to 140 tex, these two multifilament plies being put into a helix individually at 250 turns per meter in one direction, then put into a helix together at 250 turns per meter in the opposite direction. These two multifilament plies are wound in a helix around one another. As a variant, it will be possible to use a wrapping thread reinforcement element comprising a multifilament ply constituted by a thread of aliphatic polyamide monofilaments, in this case nylon, with a yarn count equal to 140 tex, and a multifilament ply constituted by a thread of aromatic polyamide monofilaments, in this case aramide, with a yarn count equal to 167 tex, these two multifilament plies being put into a helix individually at 290 turns per meter in one direction, then put into a helix together at 290 turns per meter in the opposite direction. These two multifilament plies are wound in a helix around one another. According to yet another variant, it will be possible to use a wrapping thread reinforcement element comprising two multifilament plies each constituted by a thread of aromatic polyamide monofilaments, in this case aramide, with a yarn count equal to 330 tex, and a multifilament ply constituted by a thread of aliphatic polyamide monofilaments, in this case nylon, with a yarn count equal to 188 tex, each of these multifilament plies being put into a helix individually at 270 turns per meter in one direction, then put into a helix together at 270 turns per meter in the opposite direction. These three multifilament plies are wound in a helix around one another.

[0153] In general, the use of a heavy load gives rise to a decrease in the acceptable limit speed of the tire, as well as to deterioration of its performance, for example its drift rigidity. Thus, by using one or more wrapping thread reinforcement elements with a high modulus, for example such as those described in the two final variants above comprising one or a plurality of aromatic polyamide plies, it is possible to increase the acceptable limit speed for the tire, and improve the performance, in particular its drift rigidity.

[0154] Each working wire reinforcement element is an assembly 4.26 of four steel monofilaments, and comprising an inner layer of two monofilaments and an outer layer of two monofilaments wound together in a helix around the inner layer with a pitch of 14.0 mm, for example in the direction S. An assembly 4.26 of this type has a rupture force equal to 640 N, and a diameter equal to 0.7 mm. Each steel monofilament has a diameter equal to 0.26 mm and a mechanical resistance equal to 3250 MPa. As a variant, it will also be possible to use an assembly of six steel monofilaments with a diameter equal to 0.23 mm, and comprising an inner layer of two monofilaments wound together in a helix with a pitch of 12.5 mm in a first direction, for example in the direction Z, and an outer layer of four monofilaments wound together in a helix around the inner layer with a pitch of 12.5 mm in a second direction, opposite the first direction, for example in the direction S.

[0155] As represented in FIG. 3, each carcass textile thread reinforcement element 360 comprises an assembly of at least two multifilament plies 363, 364. Each multifilament ply 363, 364 is selected from amongst a polyester multifilament ply, an aromatic polyamide multifilament ply, and an aliphatic polyamide multifilament ply, preferably selected from between a polyester multifilament ply and an aromatic polyamide multifilament ply. In this case, the assembly is selected from between an assembly off two polyester multifilament plies and an assembly of a polyester multifilament ply and an aromatic polyamide multifilament ply, and in this case is constituted by two PET multifilament plies, these two multifilament plies being put in a helix individually at 270 turns per meter in one direction, then put into a helix together at 270 turns per meter in the opposite direction. Each of these multifilament plies has a yarn count equal to 334 tex, such that the total yarn count of the assembly is 475 tex or more, and in this case equal to 668 tex. Each carcass textile thread reinforcement element 360 has a mean diameter D, expressed in mm, such that D≥0.85 mm, preferably D≥0.90 mm and such that D≤1.10 mm, preferably D≤1.00 mm. In this case, D=0.95 mm.

Assembly Fitted According to a Second Embodiment

[0156] A tire according to a second embodiment will now be described with reference to FIGS. 4 and 5. The elements which are analogous to those of the first embodiment are designated by identical references.

[0157] Unlike the first embodiment, the tire 11 is of the size 225/55R18, i.e. with a nominal cross-sectional width SW=225, a nominal aspect ratio AR=55 and a nominal rim diameter in this case equal to 18. The tire 11 according to the second embodiment has a height of sidewall H defined by SW×AR/100=124≥95, and preferably H≥100.

[0158] The marking also comprises a load rating LI ranging from 98 to 116, such that LI≥LI′+1, where LI′ is the load rating of an EXTRA LOAD tire with the same size according to the ETRTO 2019 standard. Preferably, LI′+1≤LI≤LI′+4, and even LI′+2≤LI≤LI′+4.

[0159] A tire with a size 225/55R18 in its EXTRA LOAD version has a load rating equal to 102, as indicated on page 28 of the part Passenger Car Tyres—Tyres with Metric Designation of the manual of the ETRTO 2019 standard. Thus, the load rating LI of the tire 11 is such that LI≥103, preferably 103≤LI≤106 and even 104≤LI≤106 and in this case LI=105. This load rating equal to 105 corresponds well to the load rating of a HIGH LOAD CAPACITY tire with a size of 225/55R18, as indicated in the ETRTO 2021 manual. Thus, the tire 11 is of the HIGH LOAD CAPACITY type.

[0160] For a size of this type, the manual of the ETRTO 2019 standard indicates on page 28 of the part Passenger Car Tyres—Tyres with Metric Designation, a measurement rim with a rim width code equal to 7. Thus, it will be preferable for the rim 200 of the fitted assembly which bears the tire to have a rim width code equal to the measurement rim width code for the size of the tire reduced by 0.5, in this case 6.5, i.e. having a rim width A=165.10 mm.

[0161] Each radially inner 24 and radially outer 26 working layer has respectively an axial width of T1=174 mm and T2=160.00 mm.

[0162] It will be noted that, just as in the first embodiment, SW=225 and T2=160 mm satisfy the following equations T2≥SW−75, preferably T2≥SW−70 and T2≤SW−27, preferably T2≤SW−30 and the ratio T2/A is such that 0.85≤T2/A≤1.00, preferably 0.90≤T2/A≤1.00 and more preferably 0.93≤T2/A≤0.97 and in this case T2/A=0.97.

[0163] Unlike the first embodiment, the tire 11 of the fitted assembly of the second embodiment comprises first and second layers of carcass 36, 37 delimited axially by two axial edges respectively 361, 362, 371, 372 and comprising carcass textile thread reinforcement elements respectively 360, 370 extending axially from one axial edge 361, 371 to the other axial edge 362, 372 in a main direction D3 forming an angle AC with the circumferential direction X of the tire 10, in absolute value, ranging from 80° to 90°, and in this case et AC=+90°.

[0164] Each first and second layer of carcass 36, 37 extends into each sidewall 30 and into the crown 12 radially in the interior of the crown reinforcement 16.

[0165] The first layer of carcass 36 forms a winding around each circumferential reinforcement element 33 of each bead 32, such that an axially interior portion 3611, 3621 of the first layer of carcass 36 is arranged axially in the interior of an axially exterior portion 3612, 3622 of the first layer of carcass 36, and such that each axial end 361, 362 of the first layer of carcass 36 is arranged radially on the exterior of each circumferential reinforcement element 33. Each axial end 371, 372 of the second layer of carcass 37 is arranged radially in the interior of each axial end of the first layer 361, 362, and is arranged axially between the axially interior and exterior portions 3611, 3612 and 3621, 3622 of the first layer of carcass 36.

[0166] Each axial end 361, 362 of the first layer of carcass 36 is arranged radially in the interior of the equator E of the tire. More specifically, each axial end 361, 362 of the first layer of carcass 36 is arranged at a radial distance RNC of 30 mm or less from a radially exterior end 331 of each circumferential reinforcement element 33 of each bead 32. In this case RNC=23 mm.

[0167] Each carcass textile thread reinforcement element 360, 370 of each first and second layer of carcass 36, 37 comprises an assembly of at least two multifilament plies 363, 364, 373, 374. In this case, each assembly is constituted by two multifilament plies of PET, these two multifilament plies being put in a helix individually at 420 turns per meter in one direction, then put in a helix together at 420 turns per meter in the opposite direction. Each of these multifilament plies has a yarn count equal to 144 tex, such that the total yarn count of the assembly is 475 tex or less, and in this case equal to 288 tex.

[0168] Each carcass textile thread reinforcement element 360, 370 has a mean diameter respectively D1, D2 expressed in mm such that D1≤0.90 mm and D2≤0.90 mm, preferably D1≤0.85 mm and D2≤0.85 mm and more preferably D1≤0.75 mm and D2≤0.75 mm and such that D1≥0.55 mm and D2≥0.55 mm, preferably D1≥0.60 mm and D2≥0.60 mm. In this case, D1=D2=0.62 mm.

[0169] Comparative Tests

[0170] Static Test

[0171] FIG. 6 illustrates the result of a static compression test of the tire with a size 255/35R18 identical to the first embodiment, but wherein the ratio T2/A is equal to 1.05 (tire illustrated on the left), and the tire according to the first embodiment, the ratio T2/A of which is equal to 0.97 (tire illustrated on the right). The load applied to each tire is equal to 750 kg at a pressure of 250 kPa.

[0172] It will be noted that the camber of the tire on the left is clearly greater than the camber of the tire on the right. In fact, the distance DR1 of the axis of rotation R on the ground of the tire on the left is shorter than the distance DR2 of the axis of rotation R on the ground of the tire on the right.

[0173] It will be noted in particular that the sidewalls of the tire on the right are radially straighter than the sidewalls of the tire on the left. This can be seen by comparing, at the same radial dimension of each sidewall, the distances DF1 and DF2 between the exterior surface of the sidewall situated opposite the area of contact and the plane SA perpendicular to the axis of rotation R of the tire, and passing via the support face of the rim delimiting the axial width A of the rim. This can also be seen by comparing, at the same radial dimension of each sidewall situated in line with the area of contact, the distances DF1′ and DF2′ between the exterior surface of the sidewall and the perpendicular plane SA. It can be observed that DF1>DF2 and that DF1′>DF2′.

[0174] Running Test Simulation

[0175] In order to demonstrate the advantage of the invention, the inventors simulated the running of a Pilot Sport 4 tire made by MICHELIN with the size 255/35R18 in its EXTRA LOAD version, and having a load rating equal to 94 in conformity with the ETRTO 2019 standard. This tire comprises a crown reinforcement analogous to that of the tires previously described, with the difference that the value of T2 is equal to 226.00 mm.

[0176] A plurality of fitted assemblies were simulated comprising the tire described above, fitted on to a plurality of fitting supports comprising rims with three different rim width codes, i.e. 8.5, 9 and 10. For each of these fitted assemblies, a simulation was carried out of a running test analogous to the load/speed performance test described in annex VII of Regulation no. 30 of the EEC-UNO, but in even more stressing conditions and under two different types of conditions.

[0177] With the first type of conditions reproducing usage of the tire in its EXTRA-LOAD version, a tire inflated to a pressure equal to 250 kPa under a load equal to 670 kg was simulated. It will be noted that the load applied corresponds to the load which the tire must normally be able to bear, but at a pressure of 290 kPa according to the manual of the, ETRTO 2019 standard. Thus, these first conditions reproduce under-inflated usage of the tire, which is therefore particularly stressing.

[0178] With the second type of conditions reproducing usage under a far greater load, a tire inflated to a pressure also equal to 250 kPa under a load equal to 750 kg was simulated. It will be noted that the load applied corresponds to the load which a tire with a load rating 98 at a pressure of 290 kPa must normally be able to bear according to the manual of the ETRTO 2019 standard. Thus, these two conditions reproduce overloaded and under-inflated usage of the tire, which are therefore even more stressing than the first conditions.

[0179] During these simulations, the maximum of the volumetric energy dissipation DNRJ of the calendering die was measured for a portion of the carcass reinforcement, in this case the single layer of carcass, situated in the sidewall, expressed in daN/mm.sup.2. The greater this value, the greater the dissipation of energy by the structure of the tire is, and the greater the temperature increase is. These values were related to a relative value 100, below which the energy dissipation is controlled, and above which the energy dissipation is not sufficiently controlled. These values are included in table 1 below. NT means that the fitted assembly was not tested.

TABLE-US-00001 TABLE 1 Result of the test at Result of the test at A P = 250 kPa and under P = 250 kPa and under (Inches) T2/A a load of Z = 670 kg a load of Z = 750 kg 8.5 1.05 DNRJ >120 NT 9 0.98 DNRJ <100 DNRJ <100 10 0.89 NT DNRJ <50 

[0180] These tests show that the decrease in the ratio T2/A makes it possible to control the dissipation of energy in the portion of the carcass reinforcement, in this case of the single layer of carcass, situated in the sidewall, even under a relatively heavy load, and with a pressure lower than the pressure recommended to bear the corresponding load. Thus, according to the invention, it will be possible to make T2 and/or A vary in order to obtain a ratio T2/A which makes it possible to straighten the sidewalls, and thus reduce the stresses exerted on the carcass reinforcement.

[0181] The invention is not limited to the embodiments previously described.