JP5993402B2 - Heavy duty tube tire - Google Patents

Description

  The present invention relates to a heavy duty tube tire that can reduce rolling resistance without impairing durability.

  Conventionally, in heavy-duty tires, it is desired to achieve both excellent durability performance and reduced rolling resistance.

  For example, in Patent Document 1 below, a bead apex rubber extending in a taper shape from a bead core between a carcass main body portion and a turn-up portion, a first bead apex rubber on the inner side in the tire axial direction, and a second bead on the outer side in the tire axial direction. A heavy-duty tubeless tire composed of two types of rubber, an apex rubber, and having a loss tangent tan δ of the second bead apex rubber smaller than a loss tangent tan δ of the first bead apex rubber to reduce rolling resistance. It is disclosed.

JP 2002-178724 A

  Even in the heavy load tube type tire, various proposals have been made to reduce rolling resistance. For example, it is conceivable to apply the technique described in Patent Document 1 to a heavy duty tube-type tire.

  However, since the flange shape of the regular rim is different between the heavy load tubeless tire and the heavy load tube type tire, the deformation mode of the bead portion under load is different. Therefore, when the technique described in Patent Document 1 is simply applied to a heavy duty tube-type tire, the durability performance of the bead portion may be reduced.

  The present invention has been devised in view of the above circumstances, and its main object is to provide a heavy-duty tube tire capable of improving the durability performance and rolling resistance performance in a well-balanced manner.

  The present invention relates to a carcass composed of a carcass ply in which a body portion extending from a tread portion to a bead core of a bead portion to a bead core in a bead portion and a bend portion that folds the bead core around from the inner side to the outer side in the tire axial direction. A bead apex rubber extending from the bead core in a taper shape between the bent portion and the folded portion, and a heavy load tube type tire in which a tube is mounted in a tire lumen, wherein the tire is assembled to a regular rim. In an unloaded normal state filled with normal internal pressure, the outer end in the tire radial direction of the bead core is located on the inner side in the tire radial direction of the outer end in the tire radial direction of the flange of the normal rim, The bead apex rubber includes a first bead apex rubber provided inside the tire axial direction, and the first bead. A second bead apex rubber which is provided on the outer side in the tire axial direction than the pex rubber and is made of rubber having a rubber hardness smaller than that of the first bead apex rubber and a smaller loss tangent tan δ from the outer end of the flange; Further, the tire bead apex rubber has a thickness T1o in the tire axial direction in the outer region in the tire radial direction that is smaller than a thickness T2o in the tire axial direction of the second bead apex rubber.

  In the heavy duty tube-type tire according to the present invention, a reinforcing filler having a substantially U-shaped cross section in which an inner piece extending inward in the tire axial direction of the main body portion and an outer piece extending in the tire axial direction outer side of the folded portion are connected. The outer end of the inner piece in the tire radial direction is on the outer side in the tire radial direction of the outer end of the flange, and the outer end of the first bead apex rubber in the tire radial direction of the inner piece is The outer end in the tire radial direction of the second bead apex rubber is located on the outer side in the tire radial direction from the outer end, and the outer end in the tire radial direction of the first bead apex rubber is on the outer side in the tire radial direction. It is desirable to be located.

  In the heavy duty tube tire according to the present invention, the loss tangent tan δ1 of the first bead apex rubber is 0.13 to 0.20, and the loss tangent tan δ2 of the second bead apex rubber is 0.03 to 0.03. It is desirable to be 0.07.

  In the heavy duty tube-type tire according to the present invention, the tire bead apex rubber has a thickness T1r in the tire axial direction at a position in the tire radial direction corresponding to the outer end of the flange, and at the position of the flange. The ratio T1r / Tr of the bead apex rubber with respect to the thickness Tr in the tire axial direction is preferably 0.08 to 0.30.

  In the heavy-duty tube tire according to the present invention, a tire radial position where a tire axial thickness T1 of the first bead apex rubber and a tire axial thickness T2 of the second bead apex rubber are equal to each other. It is desirable that the flange is disposed in an inner region in the tire radial direction than the outer end of the flange.

  In the heavy-duty tube tire according to the present invention, a height Ha of the first bead apex rubber from the bead base line of the outer end, and a height Hf of the inner piece from the bead base line of the inner piece, The ratio Ha / Hf is preferably 1.5 or less.

  In the heavy-duty tube tire according to the present invention, a height Ha of the first bead apex rubber from the bead base line of the outer end, and a height Hf of the inner piece from the bead base line of the inner piece, The difference Ha−Hf is desirably 10 mm or more.

  In the heavy-duty tube tire according to the present invention, the difference Hf− between the height Hf of the outer end of the inner piece from the bead base line and the height Hr of the outer end of the flange from the bead base line. Hr is preferably 15 to 40 mm.

  In the heavy duty tube-type tire of the present invention, the outer end of the bead core in the tire radial direction in the normal state is located on the inner side in the tire radial direction than the outer end of the flange in the tire radial direction. Thereby, the deformation | transformation of the bead apex rubber in the vicinity of the said outer end of the bead core at the time of load is suppressed, and the durable performance of a bead part improves. Furthermore, since the first bead apex rubber having a high rubber hardness is provided on the inner side in the tire axial direction on the side of the main body portion where the tension applied to the carcass is large, the distortion of the bead apex rubber is further reduced, and the bead portion It becomes possible to improve the durability performance.

  On the other hand, the second bead apex rubber made of rubber having a smaller loss tangent tan δ provided on the outer side in the tire axial direction than the first bead apex rubber reduces energy loss in the beads during rolling. Further, since the thickness T2o of the second bead apex rubber is larger than the thickness T1o of the first bead apex rubber at a position radially outside the outer end of the flange that is largely deformed by a load, The energy loss at the part is further reduced. Thereby, the tube-type tire rolling resistance for heavy loads is reduced.

It is sectional drawing which shows one Embodiment of the tube type tire for heavy loads of this invention. It is an expanded sectional view of the bead part of Drawing 1.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a tire meridian cross-sectional view including a tire rotation axis in a normal state of the heavy duty tube-type tire 1 of the present embodiment. Here, the normal state is a no-load state in which the tire is assembled on the normal rim RM and filled with the normal internal pressure. Hereinafter, unless otherwise specified, the dimensions and the like of each part of the tire are values measured in this normal state.

  The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based. For example, “Standard rim” for JATMA, “Design Rim” for TRA, ETRTO If so, it is "Measuring Rim".

  “Regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum air pressure for JATMA and the table “TIRE LOAD LIMITS” for TRA The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” in the case of ETRTO.

  As shown in FIG. 1, a heavy-duty tube tire (hereinafter sometimes simply referred to as “tire”) 1 according to the present embodiment is connected to a bead core 5 of a bead portion 4 from a tread portion 2 through a sidewall portion 3. The toroidal carcass 6, the belt layer 7 disposed on the outer side in the tire radial direction of the carcass 6 and on the inner side of the tread portion 2, the bead apex rubber 8 extending from the bead core 5 to the outer side in the tire radial direction, and the bead portion. 4 is provided with a U-shaped reinforcing filler 9 that reinforces 4 and a rim rubber 10 that prevents the rim from slipping and forms the outer skin of the bead portion 4.

  The heavy duty tube type tire 1 is mounted on a flat bottom rim RM with a tube (not shown) loaded in the lumen.

  The carcass 6 is formed of, for example, one carcass ply 6A in which steel carcass cords are arranged at an angle of 70 to 90 ° with respect to the tire circumferential direction. The carcass ply 6A includes a series of folded portions 6b that are folded around the bead core 5 from the inner side to the outer side in the tire axial direction at both ends of the main body portion 6a straddling the pair of bead cores 5 and 5.

  A belt layer 7 is disposed outside the carcass 6 in the radial direction and inside the tread portion 2. The belt layer 7 is formed of at least two belt plies using, for example, a steel belt cord. In this example, the first belt ply 7A in which the belt cord is arranged at an angle of, for example, 60 ± 15 ° with respect to the tire circumferential direction, and the belt cord is placed on the outer side and the belt cord is, for example, 10 The thing of the 4 sheet structure which consists of the 2nd-4th belt plies 7B-7D arranged at a small angle of -35 degrees is illustrated.

  A bead apex rubber 8 extending from the bead core 5 to the outer side in the tire radial direction through the bend portion 6b and the main body portion 6a is disposed in the bead portion 4. The bead core 5 includes a core body 5A having a polygonal cross section (for example, a hexagonal cross section) obtained by winding, for example, steel bead wires in multiple rows and stages. In the present embodiment, a configuration in which the periphery of the core body 5A is covered with the wrapping layer 5B that prevents the bead wire from being separated is illustrated. For the wrapping layer 5B, for example, a known material such as rubber or canvas is applied.

  The outer end 5o in the tire radial direction of the bead core 5 is located on the inner side in the tire radial direction from the outer end Fo in the tire radial direction of the flange F of the regular rim RM. Such an arrangement of the bead core 5 suppresses deformation of the bead apex rubber 8 in the vicinity of the outer end 5o of the bead core 5 at the time of load, and the durability performance of the bead portion 4 is improved.

  FIG. 2 shows an enlarged cross section of the bead portion 4. The bead apex rubber 8 includes a first bead apex rubber 8a provided adjacent to the main body 6a of the carcass 6 on the inner side in the tire axial direction, and the carcass 6 on the outer side in the tire axial direction than the first bead apex rubber 8a. And a second bead apex rubber 8b provided adjacent to the folded portion 6b.

  In the present embodiment, the rubber hardness of the second bead apex rubber 8b is smaller than the rubber hardness of the first bead apex rubber 8a. In this specification, “rubber hardness” is defined as rubber hardness according to durometer type A in an environment of 23 ° C. in accordance with JIS-K6253.

  In general, the tension applied to the main body 6a of the carcass 6 is greater than the tension applied to the folded portion 6b. In the present embodiment, since the first bead apex rubber 8a having a high rubber hardness is provided on the inner side in the tire axial direction on the side of the main body 6a, the distortion of the bead apex rubber 8 is effectively reduced. As a result, the durability performance of the bead portion 4 can be improved.

  The loss tangent tan δ2 of the second bead apex rubber 8b is smaller than the loss tangent tan δ1 of the first bead apex rubber 8a. Such a second bead apex rubber 8b reduces energy loss in the bead portion 4 during rolling, and reduces the rolling resistance of the heavy-duty tube tire 1. Further, the second bead apex rubber 8b suppresses heat generation in the bead portion 4 during rolling, and the durability performance of the bead portion 4 is further enhanced.

  The loss tangent tan δ1 of the first bead apex rubber 8a is preferably, for example, 0.13 to 0.20. When the loss tangent tan δ1 of the first bead apex rubber 8a is less than 0.13, the durability performance of the bead apex rubber 8 on the inner side in the tire axial direction may be deteriorated. On the other hand, when the loss tangent tan δ1 of the first bead apex rubber 8a exceeds 0.20, the energy loss at the first bead apex rubber 8a increases, and the rolling resistance of the heavy load tube tire 1 cannot be sufficiently reduced.

  For example, the loss tangent tan δ2 of the second bead apex rubber 8b is preferably 0.03 to 0.07. When the loss tangent tan δ2 of the second bead apex rubber 8b is less than 0.03, the durability performance of the bead apex rubber 8 on the outer side in the tire axial direction, that is, in the vicinity of the folded portion 6b of the carcass 6 may be deteriorated. On the other hand, when the loss tangent tan δ2 of the second bead apex rubber 8b exceeds 0.07, the effect of reducing the energy loss by the second bead apex rubber 8b is limited, and the rolling resistance of the heavy load tube tire 1 cannot be sufficiently reduced. .

  As shown in FIG. 2, the thickness T1o in the tire axial direction of the first bead apex rubber 8a in the region So outside the tire radial direction from the outer end Fo of the flange F is the second bead in the region So. It is smaller than the thickness T2o of the apex rubber 8b in the tire axial direction.

  In the heavy load tube type tire 1, the region Si located on the inner side in the tire radial direction with respect to the outer end Fo of the flange F in the bead portion 4 is constrained by the flange F and the bead core 5. It is suppressed. On the other hand, in the region So located in the tire radial direction outer side with respect to the outer end Fo of the flange F in the bead portion 4, the restraining force by the flange F gradually decreases. For this reason, the deformation of the bead portion 4 in the region So increases as the sidewall portion 3 bends outward in the tire axial direction during loading.

  In the heavy load tube type tire 1 of the present embodiment, the thickness T2o of the second bead apex rubber 8b is larger than the thickness T1o of the first bead apex rubber 8a in the region So that is greatly deformed by the load. The energy loss in the bead part 4 at the time is effectively reduced. Thereby, the tube-type tire rolling resistance for heavy loads is further reduced.

  The ratio between the thickness T1r in the tire axial direction of the first bead apex rubber 8a at the position in the tire radial direction corresponding to the outer end Fo of the flange F and the thickness Tr in the tire axial direction of the bead apex rubber 8 at the above position. T1r / Tr is, for example, preferably 0.08 or more, more preferably 0.12 or more, preferably 0.30 or less, more preferably 0.20 or less.

  When the ratio T1r / Tr is less than 0.08, the volume of the first bead apex rubber 8a is insufficient, the deformation of the bead apex rubber 8 is increased, and the durability performance and rolling resistance performance of the bead portion 4 may be reduced. There is. On the other hand, when the ratio T1r / Tr exceeds 0.30, the energy loss in the first bead apex rubber 8a increases, and the rolling resistance cannot be sufficiently reduced.

  The tire radial position Re at which the thickness T1 of the first bead apex rubber 8a in the tire axial direction and the thickness T2 of the second bead apex rubber in the tire axial direction are equal to each other is greater than the outer end Fo of the flange F in the tire radial direction. It is desirable to be disposed in the inner region Si. That is, the height Hr of the outer end Fo of the flange F from the bead base line BL, which is the tire axial direction line passing through the rim diameter position of the normal rim RM, and the height He of the position Re from the bead base line BL. The difference Hr-He is preferably a positive value.

  As already described, in the heavy load tube type tire 1, the deformation of the region Si of the bead portion 4 is suppressed by the flange F and the bead core 5. Therefore, even when the thickness of the first bead apex rubber 8a is increased in this region Si, it is considered that the influence on the rolling resistance is small. Therefore, in the present embodiment, the volume of the first bead apex rubber 8a in the vicinity of the bead core 5 is secured by arranging the position Re in the region Si. Thereby, a deformation | transformation of the bead part 4 is suppressed and the durability performance of the bead part 4 is improved further.

  The reinforcing filler 9 includes an inner piece 9a extending in the radial direction along the inner surface in the tire axial direction of the main body portion 6a of the carcass 6, and an outer piece extending in the radial direction along the outer surface in the tire axial direction of the folded portion 6b of the carcass 6. 9b is formed in a U-shape that is connected by a bottom piece 9c that passes through the inside of the bead core 5 in the radial direction. The reinforcing filler 9 is made of, for example, one reinforcing ply in which steel reinforcing cords are inclined and arranged at an angle of 40 to 70 ° with respect to the tire circumferential direction. The reinforcing filler 9 intersects the carcass cord, thereby increasing the bending rigidity of the bead portion 4 and strongly reinforcing the bead portion 4. If the angle of the reinforcing cord is less than 40 ° or exceeds 70 °, the crossing angle with the carcass cord is too small or too large, and the reinforcing effect is insufficient, and the rigidity of the bead portion 4 cannot be sufficiently increased.

  In the present embodiment, the outer end 9o in the tire radial direction of the inner piece 9a of the reinforcing filler 9 is located outside the outer end Fo of the flange F in the tire radial direction. With such a reinforcing filler 9, the carcass 6 and the bead apex rubber 8 in the region Si are wrapped by the flange F and the reinforcing filler 9. Therefore, the deformation of the bead part 4 is suppressed, and the durability performance of the bead part 4 is further enhanced.

  The outer end 8ao in the tire radial direction of the first bead apex rubber 8a is located on the outer side in the tire radial direction from the outer end 9ao of the inner piece 9a of the reinforcing filler 9. In the present embodiment, the outer end 8bo of the second bead apex rubber 8b in the tire radial direction is further positioned on the outer side in the tire radial direction than the outer end 8ao of the first bead apex rubber 8a.

  Usually, the rigidity of the flange F is very high, and it is considered that the flange F does not substantially deform. On the other hand, in the bead portion 4 of the heavy duty tube type tire 1, the reinforcing filler 9, the first bead apex rubber 8a, and the second bead apex rubber 8b have higher rigidity in this order. In this embodiment, the outer end Fo of the flange F, the outer end 9ao of the inner piece 9a of the reinforcing filler 9, the outer end 8ao of the first bead apex rubber 8a, and the outer end 8bo of the second bead apex rubber 8b are bead baselines. They are arranged in order of increasing rigidity from BL toward the outer side in the tire radial direction. Thereby, the rigidity of the bead portion 4 gradually decreases from the flange F to the maximum width portion of the heavy-duty tube tire 1. Accordingly, since stress applied to the outer end 9ao, the outer end 8ao and the outer end 8bo at the time of load is dispersed, the bead portion 4 is deformed flexibly, and the durability performance of the bead portion 4 is further enhanced.

  The ratio Ha / Hf between the height Ha of the outer end 8ao of the first bead apex rubber 8a from the bead base line BL and the height Hf of the outer end 9ao of the reinforcing filler 9 from the bead base line BL is For example, 1.5 or less is desirable.

  When the ratio Ha / Hf exceeds 1.5, the vicinity of the outer end 8ao of the first bead apex rubber 8a belongs to a region where deformation at the time of loading is large. Therefore, the energy loss in the first bead apex rubber 8a is increased, and the rolling resistance cannot be sufficiently reduced.

  The difference Ha−Hf between the height Ha of the outer end 8ao of the first bead apex rubber 8a from the bead base line BL and the height Hf of the outer end 9ao of the inner piece 9a of the reinforcing filler 9 from the bead base line BL is For example, it is preferably 10 mm or more, more preferably 15 mm or more, preferably 30 mm or less, more preferably 20 mm or less.

  When the difference Ha−Hf is less than 10 mm, the outer end 8ao of the first bead apex rubber 8a and the outer end 9ao of the inner piece 9a are too close to each other. There is a risk that the stress concentrates in the region, and the durability performance of the bead portion 4 is lowered. On the other hand, when the difference Ha−Hf exceeds 30 mm, the vicinity of the outer end 8ao of the first bead apex rubber 8a belongs to a region where deformation at the time of load is large, and the rolling resistance is sufficiently reduced as described above. Can not.

  The difference Hf−Hr between the height Hf of the outer end 9ao of the inner piece 9a of the reinforcing filler 9 from the bead base line BL and the height Hr of the outer end Fo of the flange F from the bead base line BL is preferably, for example, Is 15 mm or more, more preferably 20 mm or more, preferably 40 mm or less, more preferably 30 mm or less.

  When the difference Hf−Hr is less than 15 mm, the outer end 9ao of the inner piece 9a and the outer end Fo of the flange F are excessively close to each other, so that stress is applied in the region between the outer end 9ao and the outer end Fo during loading. There is a risk that the endurance performance of the bead portion 4 is reduced due to concentration. On the other hand, when the difference Hf−Hr exceeds 40 mm, the height Ha of the outer end 8ao of the first bead apex rubber 8a increases as the height Hf of the outer end 9ao increases. Therefore, the vicinity of the outer end 8ao of the first bead apex rubber 8a belongs to a region where deformation at the time of load is large, and the rolling resistance cannot be sufficiently reduced as described above.

  The clinch rubber 10 is arranged from the inner side in the tire radial direction of the bottom piece 9c of the reinforcing filler 9 to the outer side in the tire axial direction of the outer piece 9b. The clinching rubber 10 is exposed at least in a flange contact range in contact with the flange F, and forms the outer surface of the bead portion 4.

  As mentioned above, although the heavy load tube type tire of this invention was demonstrated in detail, this invention is changed and implemented in various aspects, without being limited to said specific embodiment.

   A heavy-duty tube tire of size 10.00R20 having the basic structure of FIG. 2 was prototyped based on the specifications shown in Table 1, and tested for rolling resistance performance and bead durability performance. In the heavy duty tube type tire of each specification, a common rubber is applied to the first bead apex rubber and the second bead apex rubber, and the hardness of the first bead apex rubber is 85 degrees. The hardness is 55 degrees. The test method is as follows.

<Rolling resistance performance>
Each sample tire was mounted on a rim 7.50 × 20, and the rolling resistance was measured using a rolling resistance tester under the conditions of an internal pressure of 790 kPa, a load of 25.01 kN, and a speed of 80 km / h. The results are displayed as an index with the value of the comparative example as 100. The smaller the numerical value, the smaller the rolling resistance and the better.

<Bead durability>
Each sample tire is mounted on a rim 7.50 × 20, and the distance until the bead portion is damaged is measured using a drum testing machine under the conditions of an internal pressure of 800 kPa, a load of 58.52 kN, and a speed of 20 km / h. It was. The results are displayed as an index with the value of the comparative example being 500. The higher the numerical value, the higher the durability and the better

  As is clear from Table 1, it was confirmed that the heavy load tube type tires of Examples were significantly improved in rolling resistance performance and bead durability performance in comparison with Comparative Examples.

1 Heavy load tube type tire 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 6a Main body part 6b Turned part 8 Bead apex rubber 8a First bead apex rubber 8ao Outer end 8b Second bead apex rubber 8bo Outer end 9 Reinforcement Filler 9a Inner piece 9ao Outer end 9b Outer piece F Flange Fo Outer end

Claims (8)

A carcass made of a carcass ply provided with a series of folded portions that folds the bead core around from the inner side to the outer side in the tire axial direction on the main body part from the tread part through the sidewall part to the bead core of the bead part;
A heavy duty tube type tire comprising a bead apex rubber extending from the bead core in a tapered shape between the main body portion and the folded portion, and a tube is mounted in a tire lumen,
In an unloaded normal state in which the tire is assembled on a normal rim and filled with a normal internal pressure, the outer end of the bead core in the tire radial direction is more tire radius than the outer end of the flange of the normal rim in the tire radial direction. Located inside the direction,
The bead apex rubber includes a first bead apex rubber provided on the inner side in the tire axial direction, and an outer side in the tire axial direction than the first bead apex rubber, and has a rubber hardness higher than that of the first bead apex rubber. A second bead apex rubber made of rubber having a small loss tangent tan δ,
The thickness of the first bead apex rubber in the tire axial direction gradually decreases from the outer end in the tire radial direction of the bead core toward the outer side in the tire radial direction,
A thickness T1o in the tire axial direction of the first bead apex rubber in an outer region in the tire radial direction from the outer end of the flange is smaller than a thickness T2o in the tire axial direction of the second bead apex rubber. A heavy duty tube-type tire. A reinforcing filler having a substantially U-shaped cross section connecting an inner piece extending in the tire axial direction inside the main body portion and an outer piece extending in the tire axial direction outer side of the folded portion;
The outer end of the inner piece in the tire radial direction is outside the outer end of the flange in the tire radial direction,
An outer end in the tire radial direction of the first bead apex rubber is located on an outer side in the tire radial direction with respect to the outer end of the inner piece,
2. The heavy duty tube-type tire according to claim 1, wherein an outer end of the second bead apex rubber in the tire radial direction is located on an outer side in the tire radial direction of an outer end of the first bead apex rubber in the tire radial direction. . 3. The heavy duty tube-type tire according to claim 1 , wherein an inner end in the tire axial direction of the second bead apex rubber is located on an outer side in the tire axial direction than an outer end in the tire radial direction of the bead core. .   A thickness T1r of the first bead apex rubber at a tire radial direction position corresponding to the outer end of the flange, and a thickness Tr1 of the bead apex rubber at the position of the flange in the tire axial direction. The heavy-duty tube tire according to any one of claims 1 to 3, wherein a ratio T1r / Tr of to is 0.08 to 0.30.   The tire radial direction position where the thickness T1 of the first bead apex rubber in the tire axial direction and the thickness T2 of the second bead apex rubber in the tire axial direction are equal to each other is the tire radial direction from the outer end of the flange. The heavy duty tube-type tire according to any one of claims 1 to 4, which is disposed in an inner region of the tire.   The ratio Ha / Hf of the height Ha from the bead base line of the outer end of the first bead apex rubber to the height Hf of the inner end from the bead base line of the inner piece is 1.5 or less. The heavy duty tube type tire according to claim 2.   A difference Ha−Hf between a height Ha of the outer end of the first bead apex rubber from the bead base line and a height Hf of the outer end of the inner piece from the bead base line is 10 mm or more. Item 7. A heavy duty tube tire according to item 2 or 6.   The difference Hf-Hr between the height Hf of the outer end of the inner piece from the bead base line and the height Hr of the outer end of the flange from the bead base line is 15 to 40 mm. The heavy duty tube-type tire according to either 6 or 7.

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