(19)
(11)EP 2 628 612 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
17.12.2014 Bulletin 2014/51

(21)Application number: 12198674.9

(22)Date of filing:  20.12.2012
(51)International Patent Classification (IPC): 
B60C 3/00(2006.01)
B60C 11/01(2006.01)
B60C 3/04(2006.01)

(54)

Pneumatic tire

Luftreifen

Pneu


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 17.02.2012 JP 2012033103

(43)Date of publication of application:
21.08.2013 Bulletin 2013/34

(73)Proprietor: Sumitomo Rubber Industries, Ltd.
Kobe-shi, Hyogo-ken (JP)

(72)Inventor:
  • Tanaka, Susumu
    Kobe-shi, Hyogo-ken, 651-0072 (JP)

(74)Representative: Manitz, Finsterwald & Partner GbR 
Martin-Greif-Strasse 1
80336 München
80336 München (DE)


(56)References cited: : 
EP-A1- 0 461 858
EP-A2- 0 119 152
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    Background of the invention


    Field of the Invention



    [0001] The present invention relates to a pneumatic tire having an improved profile which improves the ride comfort, low rolling resistance and braking performance.

    Description of the Related Art



    [0002] A pneumatic tire has a profile extending from an axially outside shoulder region of the tread portion to the sidewall portion that usually determines the ride comfort, low rolling resistance and braking performance. Referring to Fig. 3, the tire has a tread portion "a" including the shoulder portion b. In case that the profile "e" of the shoulder portion b is modified so as to have a large radius R1 of curvature shown by a virtual line from a radius R2 of curvature, since the shoulder portion b would be rounded, the ride comfort may be improved due to the reduced contact pressure acting on the shoulder portion b. Also, since the rubber thickness disposed on the shoulder portion b tends to be thinner, the rolling resistance of the tire may be decreased due to the small tire weight.

    [0003] However, such a tire is liable to have an unsatisfactory braking performance due to a small ground contact area of the tread portion.

    [0004] In order to improve the braking performance of the tire, the tread width may be enlarged so as to have a large ground contact area. However, if the tread width is enlarged, the rubber thickness on the buttress portion disposed in between the tread portion and the sidewall portion is liable to increase, and thereby the rolling resistance may deteriorate due to a heavy tire weight. Moreover, the ride comfort may also deteriorate due to the less deformation of the buttress portion.

    [0005] In order to improve various performances, a tire having a tread profile that extends along with an involutes line is proposed. The tread profile, for example, has a radius of curvature gradually decreasing from the tire equator to the axially outside of the tire so that the ground contact pressure on the tread portion is uniform in the tire axial direction, and thereby wear resistance and the steering stability may be improved.

    [0006] However, since such a profile is not sufficiently improved as for the tread shoulder portion and the sidewall portion, the ride comfort, rolling resistance and the braking performance may be deteriorated.

    SUMMARY OF THE INVENTION



    [0007] The present invention has been worked out in light of the circumstances described above, and has a main object of providing a pneumatic tire having an improved profile which improves the ride comfort, low rolling resistance and braking performance.

    [0008] In accordance with the present invention, there is provided a pneumatic tire comprising a tread portion, a pair of sidewall portions, a pair of bead portions each having a bead core therein, a carcass extending between bead cores through the tread portion and sidewall portions, a belt disposed radially outside the carcass in the tread portion, wherein in a tire meridian section including a tire axis under a standard state that the tire is mounted on a standard rim and inflated to a standard pressure but loaded with no tire load, the tread portion has a tread width TW (mm) being from 80 to 90 % of a nominal tire width YW, a profile from a shoulder region of the tread portion to the sidewall portion includes: a shoulder profile for defining the shoulder portion which is an arc having its center inside of the tire and has a radius of curvature of from 35 to 55 mm; a sidewall profile for defining at least a part of the sidewall portion which is an arc having its center inside of the tire; and a buttress profile smoothly connecting between the shoulder profile and the sidewall profile, wherein the buttress profile is an arc having its center outside of the tire and has a radius of curvature of from 20 to 60 mm.

    BRIEF DESCRIPTION OF THE DRAWINGS



    [0009] 

    Fig. 1 is a left side cross sectional view of a pneumatic tire showing an embodiment of the present invention.

    Fig. 2 is a profile of the tire of Fig. 1.

    Fig. 3 is a cross sectional view of a conventional pneumatic tire.


    DETAILED DESCRIPTION



    [0010] An embodiment of the present invention will be explained below with reference to the accompanying drawings.

    [0011] Fig. 1 shows a pneumatic tire 1 in accordance with the present embodiment, in a tire meridian section including a tire axis under a standard state. Here, the standard state is such that the tire 1 is mounted on a standard wheel rim and is inflated to a standard pressure but loaded with no tire load.

    [0012] The standard wheel rim is a wheel rim officially approved or recommended for the tire by standards organizations, the standard wheel rim is the "standard rim" specified in JATMA, the "Measuring Rim" in ETRTO, the "Design Rim" in TRA or the like, for example. The standard pressure is the "maximum air pressure" in JATMA, the "Inflation Pressure" in ETRTO, and the maximum pressure given in the "Tire Load Limits at various Cold Inflation Pressures" table in TRA or the like. In case of passenger car tires, however, the standard pressure is uniformly defined by 180 kPa.

    [0013] As shown in Fig. 1, the pneumatic tire 1 in accordance with the present embodiment comprises: a tread portion 2; a pair of sidewall portions 3 each of which extends radially inward from the axially outer end of the tread portion 2; and a pair of bead portions 4 each of which is provided radially inside the sidewall portion 3 and has a bead core 5 therein. The tire 1, for example, is illustrated as a passenger car tire having an aspect ratio of 65% in this embodiment. The aspect ratio means a ratio of a tire section height H to a nominal tire width YW.

    [0014] The tire 1 includes: a carcass 6 extending between bead cores 5 through the tread portion 2 and sidewall portions 3; and a belt 7 disposed radially outside the carcass 6 in the tread portion 2.

    [0015] The carcass 6 includes at least one carcass ply (one carcass ply is provided in this embodiment) which is composed of rubberized carcass cords arranged at an angle in the range of from 70 to 90 degrees with respect to the tire equator C. For the carcass cords, organic fiber cords, e.g. polyester, nylon, rayon, aramid and the like can be used.

    [0016] The belt 7 comprises, in this embodiment, two belt plies 7a and 7b of steel cords laid at an angle of from 10 to 35 degrees with respect to the tire equator C so that each steel cord of plies is crossed. Accordingly, the rigidity of the tread portion 2 is firmly enhanced. For the belt cords, organic fiber cords, e.g. aramid, rayon and the like can be also used.

    [0017] In order to improve the high speed durability of the tire, a band layer 8 having band cords of from 0 to 5 degrees with respect to the tire equator C is preferably provided on the belt 7. Preferably, the band 8 covers at least axially both end portions of the belt 7 to prevent the lifting thereof at high speed running. For the band cords, organic fiber cords having low elastic modulus can be preferably used.

    [0018] In the tire meridian section including the tire axis under the standard state, the tread portion 2 has a tread width TW (mm) being from 80 to 90 % of the nominal tire width YW.

    [0019] Here, the tread width TW is the width measured under the standard state, as the axial distance between the tread edges. The tread edges are the axial outermost edges of the ground contacting patch which occurs under a loaded condition when the camber angle of the tire is zero. The loaded condition is such that the tire is mounted on the standard wheel rim and inflated to the standard pressure and loaded with a standard tire load. The standard load is the "maximum load capacity" in JATMA, the "Load Capacity" in ETRTO, and the maximum value given in the above-mentioned table in TRA or the like. In case of passenger car tires, however, the standard tire load is uniformly defined by 88 % of the maximum tire load.

    [0020] Moreover, referring to Figs. 1 and 2, a tire profile L from a shoulder region 10 of the tread portion 2 to the sidewall portion 3 is improved so as to include: a shoulder profile L1 for defining the shoulder portion 10 which is an arc having its center inside of the tire and has a radius R1 of curvature of from 35 to 55 mm; a sidewall profile L2 for defining at least a part of the sidewall portion 3 which is an arc having its center inside of the tire; and a buttress profile L3 smoothly connecting between the shoulder profile L1 and the sidewall profile L2, wherein the buttress profile L3 is an arc having its center outside of the tire and has a radius R3 of curvature of from 20 to 60 mm. The tread crown portion between the shoulder portions 10, for example, has a profile having a radius TR of curvature of from 50 to 800 mm.

    [0021] Since the shoulder profile L1 has a comparatively large radius R1 of curvature of from 35 to 55 mm, contact pressure acting on the shoulder portion 10 tends to reduce, and thereby the ride comfort improves. Moreover, a rubber thickness disposed on the shoulder portion 10 tends to be thin, the rolling resistance of the tire decreases due to the weight reduction of the tire. Moreover, since the tread width TW (mm) is set in a range of from 80 to 90 % of the nominal tire width YW (mm), a large ground-contacting width of the tread portion 2 is obtained, and thereby the braking performance also improves. Moreover, since the buttress profile L3 is formed as an arc having its center outside of the tire and has a radius R3 of curvature of from 20 to 60 mm, a rubber thickness on the buttress portion tends to be thin, and thereby the rolling resistance is further reduced due to the weight reduction.

    [0022] The buttress profile L3 provides a dent on an outer surface of the tire which improves flexibility of the sidewall portion 3 when a tire load is loaded. Accordingly, the deformation of the sidewall portion 3 during running tends to be greater than that of the tread portion 2. Generally, the influence of the deformation in the tread portion 2 against the rolling resistance is greater than that of the sidewall portion 3. Therefore, since the tire 1 in accordance with the present invention has comparatively small deformation in the tread portion 2, the rolling resistance is also decreased. Moreover, since the sidewall portion 3 effectively absorbs impacts from the ground, the ride comfort is also improved.

    [0023] Here, when the tread width TW is less than 80% to the nominal tire width YW, the ground contacting area of the tread portion 2 is liable to decrease, and thereby the braking performance is deteriorated. when the tread width TW is more than 90% to the nominal tire width YW, a rubber thickness on the buttress portion and the sidewall portion 3 tend to be thick, and thereby the rolling resistance may be increased. Preferably, the tread width TW is in a range of from 85 to 90 % the nominal tire width YW.

    [0024] when the radius R1 of curvature of the shoulder profile L1 is less than 35mm, ground contact pressure acting on the tread edges tends to be large, and thereby the ride comfort is liable to deteriorate. when the radius R1 of curvature of the shoulder profile L1 is more than 55mm, sufficiently ground contact area may not be obtained. Preferably, the radius R1 of curvature of the shoulder profile L1 is in a range of from 40 to 50 mm.

    [0025] when the radius R3 of curvature of the buttress profile L3 is less than 20mm, a rubber thickness on the buttress portion tends to be thin, and thereby the stress concentration and damages may easy to occur thereon. when the radius R3 of curvature of the buttress profile L3 is more than 60mm, a rubber thickness on the buttress portion tends to be thick, and thereby the rolling resistance may be deteriorate. The radius R3 of curvature of the buttress profile L3 is more preferably not more than 45mm, still further preferably not more than 35mm, and more preferably not less than 25mm.

    [0026] The sidewall portion 3 includes a sidewall rubber 12 disposed axially outside the carcass 6. The sidewall rubber 12 has a loss tangent of less than 0.14 measured at 70 degrees celsius. The rubber composition of the sidewall rubber 12 preferably includes a polybutadiene rubber having a large amount of a linear component. The polybutadiene rubber having with a large amount of a linear component means a polybutadiene rubber having fewer branches of molecular. By adding the polybutadiene rubber described above into the rubber composition, a rubber material with a high hardness and low thermogenic may be produced. For the polymer in the rubber composition of the sidewall rubber 12, diene based rubber, such as natural rubber (NR), polybutadiene rubber other than the former one, and polyisoprene rubber (IR) may also be used.

    [0027] In order to improve the resistance of fatigue from the flexing of the sidewall portion 3 and the rolling resistance, the sidewall rubber 12 preferably has the loss tangent in a range of from 0.06 to 0.14 measured at 70 degrees celsius.

    [0028] Here, the loss tangent (tan δ) is the value obtained by measuring a specimen of 4 mm (width) x 30 mm (length) x 2 mm (thickness), in the conditions of temperature of 70 degrees celsius, amplitude of dynamic strain of plus/minus 2%, and frequency of 10Hz, by using a viscoelastic spectrometer made by IWAMOTO SEISAKUSYO.

    [0029] For a buttress rubber 13 disposed between the buttress profile L3 and the carcass 6, diene based rubber, such as natural rubber (NR), polybutadiene rubber, and polyisoprene rubber (IR) may be preferably used. Referring to Fig. 1, the buttress rubber 13 has a minimum thickness t from the buttress profile L3 to an outer surface of the carcass 6 being from 1.5 to 8 mm in order to improve the cut resistance and the rolling resistance.

    [0030] The present invention is more specifically described and explained by means of the following Examples and References. It is to be understood that the present invention is not limited to these Examples. For instance, an arc formed by multiple radiuses gradually changing may be used for each profile L1, L2 and L3. Moreover, the profiles L on both sides of the sidewall portions 2 may be formed as un-symmetrical with respect to the tire equator C.

    comparison Test



    [0031] Pneumatic tires for passenger cars of size 195/65R15 having the same internal structure of Fig. 1 except for details shown in Table 1 were made, and tested. As to the References 1 to 5 and 8, each center of radius of the buttress profiles thereof is located inside of the tire. Test methods are as follows.

    Ride comfort test:



    [0032] The test tires were mounted on wheel rims of 15x6JJ with an inner pressure of 230 kPa, and installed in a vehicle (FF car with a displacement of 1,800 cc), the test driver drove the vehicle on a test course, and evaluated ride comfort by the test driver's feelings. The results are indicated in Table 1 by scores based on Ref.1 being 6, wherein the larger the score, the better the ride comfort is.

    Braking performance test:



    [0033] The test car above was driven on the test course and suddenly braked at a speed of 100 km/hr so that the ABS worked. The braking distance of each tires were measured. The results are shown with an index of 100 representing a value in Ref. 1.

    Rolling resistance test:



    [0034] The test tire was mounted on a wheel rim of 15x6JJ with an inner pressure of 230 kPa and the rolling resistance was measured at a speed of 80 km/h and a tire load of 4.2kN, using a tester. The results are indicated by an index based on Ref.1 being 100. The smaller the index, the better the rolling resistance is.

    Durability test:



    [0035] After tests above, presence of cracks on the buttress rubber of each tire was checked.
    Table 1-1
     Ref.1Ref.2Ref.3Ref.4Ref.5Ref.6Ref. 7Ref.8Ex.1Ex.2
    Ratio TW/YW 0.78 0.78 0.85 0.85 0.85 0.85 0.94 0.94 0.8 0.8
    Radius R1 of shoulder profile (mm) 30 40 40 40 40 40 40 60 35 35
    Radius R3 of buttress profile (mm) Absence Absence Absence 15 65 Absence Absence Absence 20 60
    Loss tangent of sidewall rubber 0.14 0.14 0.14 0.14 0.14 0.06 0.14 0.14 0.14 0.14
    Ride comfort (Mark) 6 7.5 7 8 7 7 6.75 7.5 8.25 7.75
    Rolling resistance (Index) 100 94 106 96 103 100 110 100 90 93
    Braking performance (Index) 100 95 105 105 105 105 108 92 100 100
    Durability OK OK OK NG OK OK OK OK OK OK
    Table 1-2
     Ex.3Ex.4Ex.5Ex.6Ex.7Ex.8Ex.9Ex.10Ex.11Ex.12
    Ratio TW/YW 0.8 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85
    Radius R1 of shoulder profile (mm) 55 35 35 35 40 40 40 40 50 50
    Radius R3 of buttress profile (mm) 20 20 45 60 20 45 60 20 20 45
    Loss tangent of sidewall rubber 0.14 0.14 0.14 0.14 0.14 0.14 0.14 0.06 0.14 0.14
    Ride comfort (Mark) 8.75 7.75 7.5 7.25 8 7.75 7.5 8 8.25 8
    Rolling resistance (Index) 85 98 100 102 96 98 99 93 90 92
    Braking performance (Index) 95 108 108 108 105 105 105 105 102 102
    Durability OK OK OK OK OK OK OK OK OK OK
    Table 1-3
     Ex.13Ex.14Ex.15Ex.16Ex.17Ex.18Ex.19
    Ratio TW/YW 0.85 0.85 0.85 0.85 0.9 0.9 0.9
    Radius R1 of shoulder profile (mm) 50 55 55 55 35 35 55
    Radius R3 of buttress profile (mm) 60 20 45 60 20 60 20
    Loss tangent of sidewall rubber 0.14 0.14 0.14 0.14 0.14 0.14 0.14
    Ride comfort (Mark) 7.75 8.5 8.25 8 7.25 6.75 7.75
    Rolling resistance (Index) 93 90 92 94 103 105 98
    Braking performance (Index) 102 100 100 100 115 115 110
    Durability OK OK OK OK OK OK OK


    [0036] From the test results, it was confirmed that the ride comfort, rolling resistance and braking performance of example tires in accordance with the present invention can be effectively improved compared to references.


    Claims

    1. A pneumatic tire (1) comprising
    a tread portion (2),
    a pair of sidewall portions (3),
    a pair of bead portions (4) each having a bead core (5) therein,
    a carcass (6) extending between bead cores through the tread portion and sidewall portions,
    a belt (7) disposed radially outside the carcass in the tread portion, wherein
    in a tire meridian section including a tire axis under a standard state that the tire is mounted on a standard rim and inflated to a standard pressure but loaded with no tire load,
    the tread portion has a tread width TW (mm) being from 80 to 90 % of a nominal tire width YW,
    a profile from a shoulder region of the tread portion to the sidewall portion includes:

    a shoulder profile (L1) for defining the shoulder portion (10) which is an arc having its center inside of the tire and has a radius of curvature (R1) of from 35 to 55 mm;

    a sidewall profile (L2) for defining at least a part of the sidewall portion (3) which is an arc having its center inside of the tire; and

    a buttress profile (L3) smoothly connecting between the shoulder profile (L1) and the sidewall profile (L2), wherein the buttress profile is an arc having its center outside of the tire and has a radius of curvature of from 20 to 60 mm.


     
    2. The tire according to claim 1, wherein
    the tread width TW (mm) is in a range of from 85 to 90 % of the nominal tire width YW.
     
    3. The tire according to claim 1 or 2, wherein
    the radius of curvature of the shoulder profile is in a range of from 40 to 50 mm.
     
    4. The tire according to claim 1 or 2, wherein
    the radius of curvature of the buttress profile is in a range of from 20 to 45 mm.
     
    5. The tire according to claim 1 or 2, wherein
    the sidewall portion (3) includes a sidewall rubber (12) disposed axially outside the carcass, and
    the sidewall rubber has a loss tangent of less than 0.14 measured at 70 degrees celsius.
     
    6. The tire according to claim 1 or 2, wherein
    a minimum rubber thickness (t) from the buttress profile to an outer surface of the carcass is from 1.5 to 8 mm.
     


    Ansprüche

    1. Luftreifen (1), umfassend
    einen Laufflächenabschnitt (2),
    ein Paar Seitenwandabschnitte (3),
    ein Paar Wulstabschnitte (4), jeweils mit einem Wulstkern (5) darin,
    eine Karkasse (6), die sich zwischen Wulstkernen durch den Laufflächenabschnitt und Seitenwandabschnitte erstreckt,
    einen Gürtel (7), der radial außerhalb der Karkasse in dem Laufflächenabschnitt angeordnet ist, wobei
    in einem Reifenmeridianquerschnitt, der eine Reifenachse umfasst, in einem Standardzustand, in welchem der Reifen auf eine Standardfelge aufgezogen und auf einen Standarddruck aufgepumpt aber nicht mit einer Reifenlast belastet ist,
    der Laufflächenabschnitt eine Laufflächenbreite TW (mm) aufweist, die 80 bis 90 % einer Reifennennbreite YW beträgt,
    ein Profil von einem Schulterbereich des Laufflächenabschnitts zu dem Seitenwandabschnitt umfasst:

    ein Schulterprofil (L1) zum Definieren des Schulterabschnitts (10), das ein Bogen ist, dessen Zentrum innerhalb des Reifens liegt und der einen Krümmungsradius (R1) von 35 bis 55 mm aufweist;

    ein Seitenwandprofil (L2) zum Definieren zumindest eines Teils des Seitenwandabschnitts (3), das ein Bogen ist, dessen Zentrum innerhalb des Reifens liegt; und

    ein Übergangsprofil (L3), das eine glatte Verbindung zwischen dem Schulterprofil (L1) und dem Seitenwandprofil (L2) herstellt, wobei das Übergangsprofil ein Bogen ist, dessen Zentrum außerhalb des Reifens liegt und der einen Krümmungsradius von 20 bis 60 mm aufweist.


     
    2. Reifen nach Anspruch 1, wobei die Laufflächenbreite TW (mm) im Bereich von 85 bis 90 % der Reifennennbreite YW liegt.
     
    3. Reifen nach Anspruch 1 oder 2, wobei der Krümmungsradius des Schulterprofils in einem Bereich von 40 bis 50 mm liegt.
     
    4. Reifen nach Anspruch 1 oder 2, wobei der Krümmungsradius des Übergangsprofils in einem Bereich von 20 bis 45 mm liegt.
     
    5. Reifen nach Anspruch 1 oder 2, wobei
    der Seitenwandabschnitt (3) einen Seitenwandkautschuk (12) umfasst, der axial außerhalb der Karkasse angeordnet ist, und
    der Seitenwandkautschuk einen Verlusttangens von weniger als 0,14, gemessen bei 70 Grad Celsius, aufweist.
     
    6. Reifen nach Anspruch 1 oder 2, wobei eine minimale Kautschukdicke (t) von dem Übergangsprofil zu der Außenfläche der Karkasse 1,5 bis 8 mm beträgt.
     


    Revendications

    1. Bandage pneumatique (1) comprenant
    une portion formant bande de roulement (2),
    une paire de portions formant parois latérales (3),
    une paire de portions de talon (4) ayant chacune une âme de talon (5) à l'intérieur,
    une carcasse (6) s'étendant entre les âmes de talon à travers la portion formant bande de roulement et les portions formant parois latérales,
    une ceinture (7) disposée radialement à l'extérieur de la carcasse dans la portion formant bande de roulement, dans lequel
    dans une section méridienne du pneumatique incluant un axe du pneumatique dans un état standard dans lequel le pneumatique est monté sur une jante standard et gonflé à une pression standard mais sans supporter de charge sur le pneumatique,
    la portion formant bande de roulement a une largeur de roulement TW (mm) qui est de 80 à 90 % d'une largeur nominale YW du pneumatique,
    un profil depuis une région d'épaulement de la portion formant bande de roulement vers la portion formant paroi latérale inclut :

    un profil d'épaulement (L1) pour définir la portion d'épaulement (10) qui est un arc ayant son centre à l'intérieur du pneumatique et ayant un rayon de courbure (R1) de 35 à 55 mm ;

    un profil de paroi latérale (L2) pour définir au moins une partie de la portion formant paroi latérale (3) qui est un arc ayant son centre à l'intérieur du pneumatique ; et

    un profil de contrefort (L3) qui est connecté en douceur entre le profil d'épaulement (L1) et le profil de paroi latérale (L2), dans lequel le profil de contrefort est un arc ayant son centre à l'extérieur du pneumatique et ayant un rayon de courbure de 20 à 60 mm.


     
    2. Pneumatique selon la revendication 1, dans lequel
    la largeur de roulement TW (mm) est dans une plage de 85 à 90 % de la largeur nominale YW du pneumatique.
     
    3. Pneumatique selon la revendication 1 ou 2, dans lequel
    le rayon de courbure du profil d'épaulement est dans une plage de 40 à 50 mm.
     
    4. Pneumatique selon la revendication 1 ou 2, dans lequel
    le rayon de courbure du profil de contrefort est dans une plage de 20 à 45 mm.
     
    5. Pneumatique selon la revendication 1 ou 2, dans lequel
    la portion formant paroi latérale (3) inclut un caoutchouc de paroi latérale (12) disposé axialement à l'extérieur de la carcasse, et
    le caoutchouc de paroi latérale présente une tangente de perte inférieure à 0,14, mesurée à 70° C.
     
    6. Pneumatique selon la revendication 1 ou 2, dans lequel
    une épaisseur de caoutchouc minimum (t) depuis le profilé de contrefort jusqu'à une surface extérieure de la carcasse est de 1,5 à 8 mm.
     




    Drawing