TIRE COMPRISING TWO CARCASS LAYERS

Abstract

The tire (11) for a passenger vehicle comprises a crown (12), two beads (32), two sidewalls (30) each connecting each bead (32) to the crown (12), and a carcass reinforcement (34) anchored in each bead (32). The tire (11) has a load index Ll such that Ll≥Ll′+1 and Ll′ being the load index of an EXTRA LOAD tire of the same size in accordance with the manual of the ETRTO 2019 standard. The tire (11) has a sidewall height H defined by H=SW×AR/100, where SW is the nominal section width and AR is the nominal aspect ratio of the tire in accordance with the manual of the ETRTO 2019 standard, such that H≥95. The carcass reinforcement (34) comprises two carcass layers (36, 37).

Claims

1.-14. (canceled)

15. A tire (11) for a passenger vehicle, the tire comprising a crown (12), two beads (32), two sidewalls (30) each connecting each bead (32) to the crown (12), and a carcass reinforcement (34) anchored in each bead (32), the crown (12) comprising a crown reinforcement (16) and a tread (14), the carcass reinforcement (34) extending in each sidewall (30) and in the crown (12) radially on the inside of the crown reinforcement (16), wherein the tire (11) has a load index LI such that LI≥LI′+1, where LI′ is a load index of an EXTRA LOAD tire having a same size in accordance with standard ETRTO 2019, wherein the tire (11) has a sidewall height H defined by H=SW×AR/100, where SW is a nominal section width and AR is a nominal aspect ratio of the tire in accordance with standard ETRTO 2019 such that H≥95, and wherein the crown reinforcement (34) comprises first and second carcass layers (36, 37).

16. The tire (11) according to claim 15, wherein LI′+1≤LI≤LI′+4.

17. The tire (11) according to claim 15, wherein the first and second carcass layers (36, 37) are axially delimited by two axial edges (361, 362, 371, 372) of the carcass layer (36, 37) and comprise carcass textile filamentary reinforcing elements (360, 370) extending axially from one axial edge to an other axial edge of the carcass layer (36, 37) in a main direction forming an angle ranging from 80° to 90° in terms of absolute value with a circumferential direction (X) of the tire (11).

18. The tire (11) according to claim 15, wherein one of the first and second carcass layers (36, 37) forms a winding around a circumferential reinforcing element (33) of each bead such that an axially inner portion (3611, 3621) of the carcass layer (36) is arranged axially on an inside of an axially outer portion (3612, 3622) of the carcass layer (36) and such that each axial end (361, 362) of the carcass layer (36) is arranged radially on an outside of each circumferential reinforcing element (33).

19. The tire (11) according to claim 18, wherein each axial end (361, 362) of the carcass layer forming the winding is arranged radially on an inside of an equator (E) of the tire.

20. The tire (11) according to claim 15, wherein 95≤H≤155 and the first carcass layer (36) forms a winding around a circumferential reinforcing element (33) of each bead such that an axially inner portion (3611, 3621) of the first carcass layer (36) is arranged axially on an inside of an axially outer portion (3612, 3622) of the first carcass layer (36) and such that each axial end of the first carcass layer (361, 362) is arranged radially on an outside of each circumferential reinforcing element (33), and each axial end (371, 372) of the second carcass layer (37) is arranged radially on an inside of each axial end (361, 362) of the first layer (36) and is arranged axially between the axially inner portion (3611, 3621) and axially outer portion (3612, 3622) of the first carcass layer (36), or axially on an inside of the axially inner portion (3611, 3621) of the first carcass layer (36).

21. The tire (11) according to claim 15, wherein H>155 and the first carcass layer (36) forms a winding around a circumferential reinforcing element (33) of each bead such that an axially inner portion (3611, 3621) of the first carcass layer (36) is arranged axially on an inside of an axially outer portion (3612, 3622) of the first carcass layer and such that each axial end (361, 362) of the first carcass layer (36) is arranged radially on an outside of each circumferential reinforcing element (33), and each axial end (371, 372) of the second carcass layer (37) is arranged radially on an inside of each axial end (361, 362) of the first layer (36) and is arranged axially on an outside of each axially outer portion (3612, 3622) of the first carcass layer (36).

22. The tire (11) according to claim 15, wherein the nominal section width SW ranges from 225 to 315, the nominal aspect ratio AR ranges from 25 to 55, the load index LI ranges from 98 to 116, and the tire has a nominal rim diameter ranging from 18 to 23.

23. The tire (11) according to claim 15, wherein 0.88≤H/LI≤0.98.

24. The tire (11) according to claim 15, wherein the tire has a size and a load index LI selected from among the following sizes and load indexes: 225/55R18 105, 225/55ZR18 105, 205/55R19 100, 205/55ZR19 100, 235/45R21 104, 235/45ZR21 104, 285/45R22 116, 285/45ZR22 116, 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, 275/35R21 105, 275/35ZR21 105, 285/35R21 108, 285/35ZR21 108, 295/35R22 111, 295/35ZR22 111, 275/35R23 108, 275/35ZR23 108, 325/30R21 111, 325/30ZR21 111.

25. The tire (11) according to claim 15, wherein the crown reinforcement (16) comprises a working reinforcement (20) comprising a radially inner working layer (24) and a radially outer working layer (26) arranged radially on an outside of the radially inner working layer (24).

26. The tire (11) according to claim 25, wherein each working layer (24, 26) is axially delimited by two axial edges (241, 242, 261, 262) of the working layer (24, 26) and comprises working filamentary reinforcing elements extending axially from one axial edge to an other axial edge of the working layer (24, 26), substantially parallel to one another.

27. The tire (11) according to claim 26, wherein each working filamentary reinforcing element extends in a main direction forming an angle which, in terms of absolute value, is strictly greater than 10°, with a circumferential direction (X) of the tire (11).

28. The tire (11) according to claim 15, wherein the crown reinforcement (16) comprises a hoop reinforcement (22) that is axially delimited by two axial edges (281, 282) of the hoop reinforcement and comprises at least one hooping filamentary reinforcing element wound circumferentially in a helix so as to extend axially between the axial edges (281, 282) of the hoop reinforcement (22).

29. The tire (11) according to claim 28, wherein the or each hooping filamentary reinforcing element extends along a main direction forming an angle which, in terms of absolute value, is less than or equal than 10°, with a circumferential direction (X) of the tire (11).

30. A mounted assembly (10) comprising: a mounting support (100) comprising a rim (200); and a tire (11) according to claim 15, mounted on the rim (200).

31. The mounted assembly (10) according to claim 30, wherein, with 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 axially narrowest working layer (26), the axially narrowest working layer (26) having an axial width T2 expressed in mm, and the rim (200) having a rim width A according to standard ETRTO 2019 and expressed in mm, a ratio T2/A is such that T2/A≤1.00.

32. A passenger vehicle comprising at least one tire (11) according to claim 15.

33. A passenger vehicle comprising at least one mounted assembly (10) according to claim 30.

Description

[0102] The invention will be understood better on reading the following description, which is given purely by way of non-limiting example and with reference to the drawings, in which:

[0103] FIG. 1 is a view, in a meridian section plane, of a mounted assembly according to a first embodiment of the invention,

[0104] FIG. 2 is a view, in a meridian section plane, of the tyre of the mounted assembly of FIG. 1,

[0105] FIG. 3 is a view in section along the plane III-III′ of FIG. 2 illustrating the carcass reinforcement of the tyre of FIG. 1, and

[0106] FIG. 4 is a view similar to the one in FIG. 1 comparing the deflection of a mounted assembly of the prior art and that of the mounted assembly in FIG. 1.

[0107] A frame of reference X, Y, Z corresponding to the usual axial (Y), radial (Z) and circumferential (X) directions, respectively, of a tyre or of a mounted assembly is shown in the figures.

[0108] In the following description, the measurements taken are taken on an unladen and non-inflated tyre or on a section of a tyre in a meridian plane.

[0109] FIG. 1 shows a mounted assembly according to the invention, denoted by the general reference 10. The mounted assembly 10 comprises a tyre 11 and a mounting support 100 comprising a rim 200. The tyre 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.

[0110] The tyre 11 has a substantially toric shape about an axis of revolution R substantially parallel to the axial direction Y. The tyre 11 is intended for a passenger vehicle. In the various figures, the tyre 11 is depicted as new, i.e. when it has not yet been run.

[0111] The tyre 11 comprises two sidewalls 30 bearing a marking indicating the size of the tyre 11, and also a speed rating and a speed code. In this instance, the tyre 11 has a nominal section width SW ranging from 225 to 315, preferably ranging from 245 to 315 and here equal to 225. The tyre 11 also has a nominal aspect ratio AR ranging from 25 to 55, and here equal to 55. The tyre 11 has a nominal rim diameter ranging from 18 to 23 and in this case equal to 18. The tyre 11 therefore has a sidewall height H defined by SW×AR/100=124≥95, preferably H≥100.

[0112] In accordance with the invention, the marking also comprises a load index LI ranging from 98 to 116, such that LI≥LI′+1 with LI′ being the load index of an EXTRA LOAD tyre of 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.

[0113] A tyre of size 225/55R18 in its EXTRA LOAD version has a load index 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 index LI of the tyre 11 is such that LI≥103, preferably 103≤LI≤106 and even 104≤LI≤106, and in this case LI=105. This load index equal to 105 corresponds to the load index of a HIGH LOAD CAPACITY tyre of size 225/55R18 as indicated in the ETRTO 2021 manual. Thus, the tyre 11 is clearly of the HIGH LOAD CAPACITY type.

[0114] For such a size, the manual of the ETRTO 2019 standard indicates, on page 28 of the part Passenger Car Tyres—Tyres with Metric Designation, a measuring rim with a rim width code equal to 7. The rim 200 of the mounted assembly 10 is thus selected from among: [0115] a rim having a rim width code equal to the measuring rim width code for the size of the tyre and defined according to the manual of the ETRTO 2019 standard, and [0116] a rim having a rim width code equal to the measuring rim width code for the size of the tyre minus 0.5, and [0117] a rim having a rim width code equal to the measuring rim width code for the size of the tyre plus 0.5.

[0118] In this case, the rim 200 of the mounted assembly 10 is the rim having a rim width code equal to the measuring rim width code for the size of the tyre minus 0.5 and therefore in this case equal to 6.5. The rim 200 has a profile of type J and a rim width A according to the manual of the ETRTO 2019 standard. In this instance, with the profile of the rim 200 being of type 6.5 J, its rim width A expressed in mm is equal to 165.10 mm.

[0119] With reference to FIG. 2, the tyre 11 comprises a crown 12 comprising a tread 14 intended to come into contact with the ground when the tyre is running and a crown reinforcement 16 extending in the crown 12 in the circumferential direction X. The tyre 11 also comprises a layer 18 that is airtight with respect to an inflation gas and is intended to delimit an internal cavity closed with the mounting support 100 for the tyre 11 once the tyre 11 has been mounted on the mounting support 100.

[0120] 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 inner working layer 24 arranged radially on the inside of a radially outer working layer 26. Of the radially inner layer 24 and the radially outer layer 26, the axially narrowest layer is the radially outer layer 26.

[0121] The hoop reinforcement 22 comprises at least one hooping layer and in this case comprises one hooping layer 28.

[0122] The crown reinforcement 16 is surmounted radially by the tread 14. In this case, the hoop reinforcement 22, in this case the hooping layer 28, is arranged radially on the outside of the working reinforcement 20 and is therefore interposed radially between the working reinforcement 20 and the tread 14.

[0123] The two sidewalls 30 extend the crown 12 radially towards the inside. The tyre 11 also has two beads 32 radially on the inside of the sidewalls 30. Each sidewall 30 connects each bead 32 to the crown 12.

[0124] The tyre 11 comprises a carcass reinforcement 34 that is anchored in each bead 32 and, in this instance, forms a winding around a circumferential reinforcing element 33, in this case a bead wire. The carcass reinforcement 34 extends radially in each sidewall 30 and axially in the crown 12, radially on the inside 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 first and second carcass layers 36, 37. Each first and second carcass layer 36, 37 extends in each sidewall 30 and in the crown 12 radially on the inside of the crown reinforcement 16.

[0125] The hoop reinforcement 22, in this case the hooping layer 28, is axially delimited by two axial edges 281, 282 and comprises one or more hooping filamentary reinforcing elements that are wound circumferentially in a helix between each axial edge 281, 282 along a main direction forming an angle AF which, in terms of absolute value, is less than or equal to 10°, preferably less than or equal to 7° and more preferably less than or equal to 5° with the circumferential direction X of the tyre 10. In this case, AF=−5°.

[0126] Each radially inner working layer 24 and radially outer working layer 26 is axially delimited by two axial edges 241, 242, 261, 262, respectively, of each working layer 24, 26. The radially inner working layer 24 has an axial width T1=174.00 mm and the radially outer working layer 26 has an axial width T2=160.00 mm, making the radially outer working layer 26 the axially narrowest working layer.

[0127] Note that SW=225 and T2=160 satisfy the following relationships T2≥SW−75, preferably T2≥SW−70 and T2≤SW−27, preferably T2≤SW−30.

[0128] As illustrated in FIG. 1, the mounted assembly 10 is such that the tyre 11 has radially straightened sidewalls. To be specific, 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.

[0129] Each working layer 24, 26 comprises working filamentary reinforcing 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 along main directions forming oppositely oriented angles AT1 and AT2, respectively, which, in terms of absolute value, are strictly greater than 10°, preferably ranging from 15° to 50° and more preferably ranging from 20° to 35°, with the circumferential direction X of the tyre 10. In this case, AT1=−26° and AT2=+26°.

[0130] Each first and second carcass layer 36, 37 is axially delimited by two axial edges 361, 362, 371, 372, respectively, and comprises carcass textile filamentary reinforcing elements 360, 370, respectively, extending axially from one axial edge 361, 371 to the other axial edge 362, 372 in a main direction D3 forming an angle AC which, in terms of absolute value, ranges from 80° to 90°, and in this case AC=+90°, with the circumferential direction X of the tyre 10.

[0131] The first carcass layer 36 forms a winding around each circumferential reinforcing element 33 of each bead 32 such that an axially inner portion 3611, 3621 of the first carcass layer 36 is arranged axially on the inside of an axially outer portion 3612, 3622 of the first carcass layer 36 and such that each axial end 361, 362 of the first carcass layer 36 is arranged radially on the outside of each circumferential reinforcing element 33. Each axial end 371, 372 of the second carcass layer 37 is arranged radially on the inside of each axial end of the first layer 361, 362 and is arranged axially between the axially inner and outer portions 3611, 3612 and 3621, 3622 of the first carcass layer 36.

[0132] Each axial end 361, 362 of the first carcass layer 36 is arranged radially on the inside of the equator E of the tyre. More specifically, each axial end 361, 362 of the first carcass layer 36 is arranged at a radial distance RNC of less than or equal to 30 mm from a radially inner end 331 of each circumferential reinforcing element 33 of each bead 32. In this case, RNC=23 mm.

[0133] Each working layer 24, 26, hooping layer 28 and carcass layer 36 comprises a calendering matrix for the filamentary reinforcing elements of the corresponding layer. Preferably, the calendering matrix is polymeric and more preferably elastomeric, like those usually used in the field of tyres.

[0134] Each hooping filamentary reinforcing element conventionally comprises two multifilament plies, each multifilament ply being made up of a spun yarn of aliphatic polyamide, in this case nylon, monofilaments with a count equal to 140 tex, these two multifilament plies being twisted in a helix individually at 250 turns per metre in one direction and then twisted together in a helix at 250 turns per metre in the opposite direction. These two multifilament plies are wound in a helix around one another. As a variant, use could be made of a hooping filamentary reinforcing element comprising one multifilament ply made up of a spun yarn of aliphatic polyamide, in this case nylon, monofilaments with a count equal to 140 tex, and one multifilament ply made up of a spun yarn of aromatic polyamide, in this case aramid, monofilaments with a count equal to 167 tex, these two multifilament plies being twisted in a helix individually at 290 turns per metre in one direction and then twisted together in a helix at 290 turns per metre in the opposite direction. These two multifilament plies are wound in a helix around one another. In yet another variant, use could be made of a hooping filamentary reinforcing element comprising two multifilament plies each made up of a spun yarn of aromatic polyamide, in this case aramid, monofilaments with a thread count equal to 330 tex, and one multifilament ply made up of a spun yarn of aliphatic polyamide, in this case nylon, monofilaments with a thread count equal to 188 tex, each of the multifilament plies being twisted in a helix individually at 270 turns per metre in one direction and then twisted together in a helix at 270 turns per metre in the opposite direction. These three multifilament plies are wound in a helix around one another.

[0135] In general, the use of a high load leads to a reduction in the acceptable limit speed of the tyre and also a deterioration of its behaviour, for example its cornering stiffness. Thus, by using one or more high-modulus hooping filamentary reinforcing elements, for example like those described in the last two variants above comprising one or more aromatic polyamide strands, it is possible to increase the acceptable limit speed for the tyre and to improve the behaviour, in particular its cornering stiffness.

[0136] Each working filamentary reinforcing element is an assembly 4.26 of four steel monofilaments, comprising an inner layer of two monofilaments and an outer layer of two monofilaments wound together in a helix around the inner layer at a pitch of 14.0 mm, for example in the direction S. Such an assembly 4.26 has a force at break equal to 640 N, a diameter equal to 0.7 mm. Each steel monofilament has a diameter equal to 0.26 mm and a mechanical strength equal to 3250 MPa. As a variant, use could also be made of an assembly of six steel monofilaments having a diameter equal to 0.23 mm, comprising an internal layer of two monofilaments wound together in a helix at a pitch of 12.5 mm in a first direction, for example the Z direction, and an external layer of four monofilaments wound together in a helix around the internal layer at a pitch of 12.5 mm in a second direction, opposite to the first direction, for example the S direction.

[0137] As shown in FIG. 3, each carcass textile filamentary reinforcing element 360, 370 of each first and second carcass layer 36, 37 comprises an assembly of at least two multifilament plies 363, 364 and 373, 374. Each multifilament ply 363, 364, 373, 374 is selected from among a polyester multifilament ply, an aromatic polyamide multifilament ply and an aliphatic polyamide multifilament ply, preferably selected from among a polyester multifilament ply and an aromatic polyamide multifilament ply. In this instance, the assembly is selected from an assembly of two polyester multifilament plies and an assembly of a polyester multifilament ply and an aromatic polyamide multifilament ply, and in this case is made up of two PET multifilament plies, these two multifilament plies being twisted in a helix individually at 420 turns per metre in one direction and then twisted together in a helix at 420 turns per metre in the opposite direction. Each of these multifilament plies has a thread count equal to 114 tex such that the total thread count of the assembly is less than or equal to 475 tex and in this case equal to 228 tex.

[0138] Each carcass textile filamentary reinforcing element 360, 370 has an average diameter D1, D2, respectively, 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.

[0139] A tyre according to a second embodiment of the invention will now be described.

[0140] By contrast to the first embodiment, the tyre according to the second embodiment has a nominal section width SW equal to 255, a nominal aspect ratio AR equal to 40, a nominal rim diameter equal to 21 and a sidewall height H defined by SW×AR/100=102, which is greater than or equal to 95. A tyre of size 255/40R21 in its EXTRA LOAD version has a load index equal to 102 as indicated on page 34 of the part Passenger Car Tyres—Tyres with Metric Designation of the manual of the ETRTO 2019 standard. Thus, the load index LI of the tyre according to the second embodiment is such that LI≥103, preferably 103≤LI≤106 and even 104≤LI≤106, and in this case LI=105. This load index equal to 105 corresponds to the load index of a HIGH LOAD CAPACITY tyre of size 255/40R21 as indicated in the ETRTO 2021 manual. Thus, the tyre according to the second embodiment is indeed of the HIGH LOAD CAPACITY type.

[0141] Unlike the tyre according to the first embodiment, the tyre according to the second embodiment is such that 0.88≤H/LI≤0.98 and in this case H/LI=0.97.

[0142] Comparative Tests

[0143] Tensioning Simulation

[0144] In order to demonstrate the advantage of the invention, the inventors simulated the tension of each carcass filamentary reinforcing element of multiple tyres.

[0145] For each of these tests, the tension of each carcass filamentary reinforcing element was simulated for tyres inflated to a pressure equal to 2.8 bar and subjected to a load much higher than that used for the load/speed performance test described in Annex VII of UN/ECE Regulation No 30.

[0146] Various tyres of the following sizes 255/35 R20, 235/60 R18, 255/60 R18 were simulated such that: [0147] the tyre has a carcass reinforcement comprising first and second carcass layers according to the invention (denoted by the references INV1, INV2), wherein each axial end of the second carcass layer is arranged radially on the inside of each axial end of the first layer and is arranged axially between the axially inner and outer portions of the first carcass layer (first configuration), [0148] the tyre has a carcass reinforcement comprising first and second carcass layers according to the invention (denoted by the references INV1′, INV2′), wherein each axial end of the second carcass layer is arranged radially on the inside of each axial end of the first layer and is arranged axially on the outside of each axially outer portion of the first carcass layer (second configuration), [0149] the tyre comprises a carcass reinforcement similar to that of the tyres INV1 and INV2 but has a sidewall height H strictly less than 95 (COMP0), and [0150] the tyre comprises a single carcass reinforcement (COMP1, COMP2) and has a sidewall height H strictly less than 95 (COMP0′).

[0151] The tension of each carcass filamentary reinforcing element is measured at the end of the single carcass layer for tyres comprising a single carcass layer and at the end of the first carcass layer forming the winding around the circumferential reinforcing element of each bead for tyres comprising two carcass layers.

[0152] The results of these simulations are collated in Table 1 below.

TABLE-US-00001 TABLE 1 Dimension 255/35 R20 255/35 R20 235/60 R18 235/60 R18 235/60 R18 255/60 R18 255/60 R18 255/60 R18 H 89 89 141 141 141 153 153 153 Tyre COMP0 COMP0′ INV1 INV1′ COMP1 INV2 INV2′ COMP2 designation Tension 0.22 0.46 0.34 0.36 0.71 0.42 0.42 0.79 (daN)

[0153] First of all, it is shown that the tension of the carcass filamentary reinforcing elements is significantly reduced in the case of tyres having first and second carcass layers, by contrast to the tyres having a single carcass layer. Thus, by virtue of the use of first and second carcass layers, the tension of the carcass reinforcement is controlled.

[0154] Moreover, this control of the tension of the carcass reinforcement proves to be necessary only for tyres having a sidewall height greater than or equal to 95. This is because the tension of the carcass reinforcement of tyres having a sidewall height strictly less than 95 remains controlled, even in the case of a carcass reinforcement comprising a single carcass layer.

[0155] It will also be noted that, for a given number of carcass layer(s), the tension is all the greater the taller the sidewall is. Thus, if a reduction in the tensioning of the carcass reinforcement to a reasonable level with an arrangement of the carcass reinforcement according to the first configuration is desired, the sidewall height will be limited to values less than or equal to 155. For sidewall heights strictly greater than 155, preference will be given, as explained above, to an arrangement of the carcass reinforcement according to the second configuration, so as to reduce this tensioning.

[0156] Simulation of Running Tests

[0157] In order to demonstrate the optional advantage of the arrangement of the carcass reinforcement of the first configuration over the second configuration for tyres having a sidewall height less than or equal to 155, the inventors simulated running of the tyres.

[0158] For each of these tests, running similar to the load/speed performance test described in Annex VII of UN/ECE Regulation No 30 was simulated, but under even more demanding load and pressure conditions. Various tyres of the following sizes 255/40 R21, 235/60 R18 and 255/60 R18 were simulated such that: [0159] the tyre comprises an arrangement of the carcass reinforcement according to the first configuration (denoted by the references INV1, INV2, INV3), [0160] the tyre comprises an arrangement of the carcass reinforcement according to the second configuration (denoted by the references INV1′, INV2′, INV3′).

[0161] During these simulations, the maximum volumetric energy dissipation DNRJ of a portion of the calendering matrices of the first and second carcass layers was recorded, this portion being located axially between the first and second carcass layers and in the sidewall, and expressed in daN/mm2. The higher this value, the greater the energy dissipation by the tyre structure and the greater the rise in temperature. The results of these simulations are collated in Table 2 below.

TABLE-US-00002 TABLE 2 Dimension 255/40 R21 255/40 R21 235/60 R18 235/60 R18 255/60 R18 255/60 R18 H 102 102 141 141 153 153 Tyre INV3 INV3′ INV1 INV1′ INV2 INV2′ designation DNRJ 0.038 0.06 0.005 0.009 0.005 0.01

[0162] It will be noted that the arrangement of the carcass reinforcement according to the first configuration is advantageous for reducing the energy dissipation, and that an arrangement of the carcass reinforcement according to the second configuration does not make it possible to reduce the energy dissipation as much. That is particularly advantageous for sidewall heights H≤130, preferably H≤120 and more preferably H≤110. This is because, for such sidewall heights, since the maximum volumetric energy dissipation DNRJ is relatively high, the use of the arrangement of the carcass reinforcement according to the first configuration makes it possible to significantly reduce the energy dissipation to an acceptable level in terms of absolute value.

[0163] Even if the energy dissipation, in terms of absolute value, is less for sidewall heights greater than 130 than for sidewall heights less than or equal to 130, the arrangement of the carcass reinforcement according to the first configuration nevertheless makes it possible to reduce this energy dissipation by approximately 50%.

[0164] Static Test

[0165] In order to illustrate the effect of straightening the sidewalls, which, although advantageous, is optional within the scope of the invention, FIG. 4 illustrates the result of a static compression test on a tyre of size 225/55R18, which is identical to the tyre described above but for which the ratio T2/A is equal to 1.05 (tyre illustrated on the left-hand side) and the tyre described above for which the ratio T2/A is equal to 0.97 (tyre illustrated on the right-hand side). The load applied to each tyre is equal to 925 kg at a pressure of 250 kPa.

[0166] It will be noted that the deflection of the left-hand tyre is much greater than the deflection of the right-hand tyre. This is because the distance DR1 from the axis of rotation R to the ground in the left-hand tyre is less than the distance DR2 from the axis of rotation R to the ground in the right-hand tyre.

[0167] It will be noted in particular that the sidewalls of the right-hand tyre are radially straighter than the sidewalls of the left-hand tyre. This can be seen by comparing, at the same radial point on each sidewall, the distances DF1 and DF2 between the outer surface of the sidewall located on the opposite side to the contact patch and the plane SA that is perpendicular to the axis of rotation R of the tyre and passes through the bearing face of the rim delimiting the axial width A of the rim. This can also be seen by comparing, at the same radial point on each sidewall located in line with the contact patch, the distances DF1′ and DF2′ between the outer surface of the sidewall and the perpendicular plane SA. It will be observed that DF1>DF2 and that DF1′>DF2′.

[0168] The invention is not limited to the embodiments described above.