JP2015128912A - pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire which is reduced in an air column resonant sound, and reduced in rolling resistance.SOLUTION: In this tire 2, an axial width of a first layer 46 of a base layer 28 is set small toward the inside from the outside of a radial direction. The first layer 46 contacts with a reinforcing layer 44. An axial width of a second layer 48 of the base layer 28 is set large toward the inside from the outside of the radial direction. The second layer 48 contacts with the reinforcing layer 44, and constitutes a bottom face 22a of a main groove 22. An axial width Wa of the first layer 46 at the outside of the radial direction is set not smaller than an axial width Wt of a land part tread face 26 located outside the radial direction. A loss tangent tanδ1 of the first layer 46 is set smaller than a loss tangent tanδ2 of the second layer 48.

Description

  The present invention relates to a pneumatic tire.

  As the vehicle travels, the tires roll on the road surface. The ground contact surface of the tire moves in the circumferential direction. The tire tread is repeatedly deformed in the circumferential direction. In a tire including a main groove extending continuously in the circumferential direction, air column resonance is generated in the main groove. This air column resonance sound is a sound having a frequency of 800 Hz to 1000 Hz, and is also called a shear sound. This air column resonance is a major cause of outside noise when the vehicle passes.

  By reducing the groove volume of the main groove, the air column resonance can be reduced. However, reducing the groove volume of the main groove hinders drainage performance. This tire tends to be inferior in hydroplaning performance.

  In place of reducing the groove volume of the main groove, a tire that reduces air column resonance noise by changing the rigidity of the tread has been proposed. Patent Document 1 discloses a tire in which noise is reduced by sandwiching an isolation rubber layer between belt plies. Patent Document 2 discloses a tire in which noise is reduced by setting rubber hardness, loss tangent tan δ, and thickness of a cap layer and a base layer of a tread within predetermined ranges.

Japanese Unexamined Patent Publication No. 7-69004 JP 2002-240510 A

  However, in the tires of Patent Document 1 and Patent Document 2, energy loss increases. These tires increase the rolling resistance. It is not easy to reduce the air column resonance noise of the main groove while maintaining other performance such as hydroplaning performance and rolling resistance.

  An object of the present invention is to provide a tire in which air column resonance noise is reduced and rolling resistance is reduced.

A tire according to the present invention includes a tread whose outer surface forms a tread surface, a pair of sidewalls that extend substantially inward in the radial direction from the end of the tread, and a pair of beads that are positioned radially inward of the sidewalls. And a carcass spanned between one bead and the other bead along the inside of the tread and the sidewall, and a reinforcing layer laminated with the carcass on the radially inner side of the tread. A main groove extending in the circumferential direction is formed on the tread surface. The tread surface is a land tread surface that is divided into main grooves and arranged in the axial direction.
The tread includes a base layer and a cap layer laminated on the outer side in the radial direction of the base layer. The base layer includes a first layer located on the inner side in the radial direction of the land tread surface and a second layer located on the inner side in the radial direction of the main groove.
The axial width of the first layer is reduced from the radially outer side to the inner side. The first layer is in contact with the reinforcing layer.
The axial width of the second layer is increased from the radially outer side to the inner side. The second layer is in contact with the reinforcing layer. The second layer constitutes the bottom surface of the main groove.
The axial width Wa on the outer side in the radial direction of the first layer is greater than or equal to the axial width Wt of the land tread surface located on the outer side in the radial direction.
The loss tangent tan δ1 of the first layer is smaller than the loss tangent tan δ2 of the second layer.

  Preferably, in this tire, the ratio Wb / Wt of the axial width Wb between the first layer and the reinforcing layer and the axial width Wt of the land tread surface is 1/5 or more and 1/3 or less. Has been.

  Preferably, in this tire, the thickness T1 of the first layer is larger than the thickness Tg of the tread at the bottom of the main groove. More preferably, in this tire, the thickness T1 of the first layer is not less than 2 mm and not more than 3 mm.

  Alternatively, in this tire, the ratio tan δ1 / tan δ2 between the loss tangent tan δ1 of the first layer and the loss tangent tan δ2 of the second layer is set to 0.4 or more and 0.8 or less.

  In the tire according to the present invention, since the second layer is located on the inner side in the radial direction of the main groove, the transmission of vibration from the belt to the main groove is suppressed. Thereby, generation | occurrence | production of the air column resonance sound of a main groove is suppressed. Since the first layer is located inside the tread surface, the rolling resistance is reduced. In this tire, generation of air column resonance in the main groove is suppressed, and rolling resistance is reduced.

FIG. 1 is a cross-sectional view showing a part of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a partially enlarged view of FIG.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

  FIG. 1 shows a pneumatic tire 2. In FIG. 1, the vertical direction is the radial direction of the tire 2, the horizontal direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the circumferential direction of the tire 2. In FIG. 1, an alternate long and short dash line CL represents the equator plane of the tire 2. The shape of the tire 2 is symmetric with respect to the equator plane CL except for the tread pattern.

  The tire 2 includes a tread 4, a sidewall 6, a clinch 8, a bead 10, a carcass 12, a belt 14, a band 16, and an inner liner 18. The tire 2 is a tubeless type. The tire 2 is mounted on a passenger car.

  The tread 4 has a shape protruding outward in the radial direction. The tread 4 forms a tread surface 20 that contacts the road surface. A main groove 22 is carved in the tread 4. The main groove 22 extends in the circumferential direction of the tire 2. The main groove 22 goes around the tread surface 20 in the circumferential direction. The main groove 22 includes a bottom surface 22a facing outward in the radial direction and a pair of wall surfaces 22b extending from the bottom surface 22a to the tread surface 20 so as to face each other. Although not shown, the tread 4 is further formed with other grooves. A plurality of blocks 24 are formed in the tread 4 by the main groove 22 and other grooves. The outer peripheral surfaces of the plurality of blocks 24 form a land tread surface 26. The tread surface 20 is composed of a set of land portion tread surfaces 26. A tread pattern is formed by the main groove 22 and other grooves.

  The tread 4 has a base layer 28 and a cap layer 30. The base layer 28 is located on the radially inner side of the cap layer 30. The cap layer 30 is laminated on the base layer 28. The base layer 28 is made of a crosslinked rubber having excellent adhesiveness. A typical base rubber of the base layer 28 is natural rubber. The cap layer 30 is made of a crosslinked rubber having excellent wear resistance, heat resistance, and grip properties.

  The sidewall 6 extends substantially inward in the radial direction from the end of the tread 4. A radially outer end of the sidewall 6 is joined to the tread 4. The radially inner end of the sidewall 6 is joined to the clinch 8. This sidewall 6 is made of a crosslinked rubber having excellent cut resistance and weather resistance. This sidewall 6 prevents the carcass from being damaged.

  The clinch 8 is located substantially inside the sidewall 6 in the radial direction. The clinch 8 is located on the outer side in the axial direction of the bead 10 and the carcass 12. The clinch 8 is made of a crosslinked rubber having excellent wear resistance. The clinch 8 comes into contact with a rim flange when assembled to a rim (not shown).

  The bead 10 is located inside the clinch 8 in the axial direction. The bead 10 includes a core 32 and an apex 34 that extends radially outward from the core 32. The core 32 has a ring shape and includes a wound non-stretchable wire. A typical material for the wire is steel. The apex 34 is tapered outward in the radial direction. The apex 34 is made of a highly hard crosslinked rubber.

  The carcass 12 includes a first ply 36 and a second ply 38. The first ply 36 and the second ply 38 are bridged between the beads 10 on both sides, and extend along the tread 4 and the sidewall 6. The first ply 36 is folded around the core 32 from the axially inner side to the outer side. The second ply 38 is folded around the core 32 from the inner side to the outer side in the axial direction. The end of the folded portion of the first ply 36 is located outside the end of the folded portion of the second ply 38 in the radial direction.

  Each of the first ply 36 and the second ply 38 includes a plurality of cords arranged in parallel and a topping rubber. The absolute value of the angle formed by each cord with respect to the equator plane is 75 ° to 90 °. In other words, the carcass 12 has a radial structure. The cord is made of organic fiber. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers. The carcass 12 may be formed from a single ply.

  The belt 14 is located on the inner side in the radial direction of the tread 4. The belt 14 is laminated on the outer side in the radial direction of the carcass 12. The belt 14 reinforces the carcass 12. The belt 14 includes an inner layer 40 and an outer layer 42. As apparent from FIG. 1, the width of the inner layer 40 is slightly larger than the width of the outer layer 42 in the axial direction. Although not shown, each of the inner layer 40 and the outer layer 42 is composed of a large number of cords arranged in parallel and a topping rubber. Each cord is inclined with respect to the equator plane CL. The general absolute value of the tilt angle is 10 ° or more and 35 ° or less. The inclination direction of the cord of the inner layer 40 with respect to the equator plane CL is opposite to the inclination direction of the cord of the outer layer 42 with respect to the equator plane CL. A preferred material for the cord is steel. An organic fiber may be used for the cord. The axial width of the belt 14 is preferably 0.7 times or more the maximum width of the tire 2. The belt 14 may include three or more layers.

  The band 16 is located on the radially outer side of the belt 14. In the axial direction, the width of the band 16 is larger than the width of the belt 14. Although not shown, the band 16 is made of a cord and a topping rubber. The cord is spirally wound in the circumferential direction. The band 16 has a so-called jointless structure. The cord extends substantially in the circumferential direction. The angle of the cord with respect to the circumferential direction is 5 ° or less, and further 2 ° or less. Since the belt 14 is restrained by this cord, lifting of the belt 14 is suppressed. The cord is made of organic fiber. Examples of preferable organic fibers include nylon fibers, polyester fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

  The belt 14 and the band 16 constitute a reinforcing layer 44. The reinforcing layer 44 may be configured only from the belt 14 without the band 16.

  The inner liner 18 is located inside the carcass 12. In the vicinity of the equator plane CL, the inner liner 18 is joined to the inner surface of the carcass 12. The inner liner 18 is made of a crosslinked rubber. For the inner liner 18, rubber having excellent air shielding properties is used. A typical base rubber of the inner liner 18 is butyl rubber or halogenated butyl rubber. The inner liner 18 maintains the internal pressure of the tire 2.

  The base layer 28 includes a first layer 46 and a second layer 48. The first layer 46 and the second layer 48 are made of a crosslinked rubber. The loss tangent tan δ1 of the first layer 46 is made smaller than the loss tangent tan δ2 of the second layer 48. For example, the loss tangent tan δ1 is 0.05 or more and 0.15 or less. The loss tangent tan δ2 is not less than 0.10 and not more than 0.30.

  The first layer 46 is located inside the land tread surface 26 in the radial direction. The first layer 46 is laminated on the outer side in the radial direction of the reinforcing layer 44. In the tire 2 that does not include the band 16, the first layer 46 may be laminated on the outer side in the radial direction of the belt 14. A cap layer 30 is stacked on the radially outer side of the first layer 46.

  A double-headed arrow T1 in FIG. 2 indicates the thickness of the first layer 46 in the radial direction. A double arrow Wa and a double arrow Wb indicate the axial width of the first layer 46. The width Wa indicates the width on the outer side in the radial direction. The width Wb indicates the width on the inner side in the radial direction. The width Wb indicates a width where the first layer 46 and the reinforcing layer 44 are in contact with each other. The axial width of the first layer 46 is gradually reduced from the radially outer side to the inner side. The first layer 46 is gradually reduced from the width Wa to the width Wb. The thickness T1, the width Wa, and the width Wb are measured by a cross section cut out from the tire 2 as shown in FIG.

  A double arrow Wt in FIG. 2 indicates the axial width of the land tread surface 26 sandwiched between the main grooves 22. This width Wt is measured along the tread surface 26. An alternate long and short dash line Lt indicates a center line of the land tread surface 26. A one-dot chain line Lb indicates a center line of the width Wb. A double-headed arrow D indicates a positional shift between the center line Lt of the land portion tread surface 26 and the center line Lb of the width Wb. This positional deviation D is measured as a linear distance in the axial direction between the center line Lt and the center line Lb.

  The second layer 48 is laminated on the outer side in the radial direction of the reinforcing layer 44. In the tire 2 that does not include the band 16, the second layer 48 may be laminated on the outer side in the radial direction of the belt 14. The outer surface in the radial direction of the second layer 48 constitutes the bottom surface 22 a of the main groove 22. The second layer 48 extends from the bottom surface 22a of the main groove 22 to the reinforcing layer 44 in the radial direction.

  A double-headed arrow Tg in FIG. 2 indicates the thickness of the second layer 48 in the radial direction. The thickness Tg indicates the thickness of the tread 4 at the bottom surface 22a of the main groove 22. The axial width of the second layer 48 is gradually reduced from the radially outer side to the inner side.

  The side surface 46a of the first layer 46 and the side surface 48a of the second layer 48 are joined. In the base layer 28, the first layers 46 and the second layers 48 are alternately arranged in the axial direction. In the tire 2, the width Wa of the first layer 46 is larger than the width Wt of the land portion tread surface 26.

  The tire 2 is attached to the vehicle. When the vehicle travels, the tire 2 rolls. The ground contact surface of the tread surface 22 moves in the circumferential direction. In the tread 4, one rotation of the tire 2 is taken as one cycle, and a portion where the tire is compressed and deformed due to contact moves in the circumferential direction. The tread 4 repeats this periodic deformation.

  When the tread surface 22 is grounded, vibration is input to the belt 14 via the tread 4. Since the bottom surface 22a of the main groove 22 is not grounded, the bottom surface 22a is not restrained by the ground. The unconstrained bottom surface 22a is likely to vibrate. The bottom surface 22 a is composed of the second layer 48. Since the loss tangent tan δ2 of the second layer 48 is increased, vibration is hardly transmitted. It is suppressed that the vibration of the belt 14 is transmitted to the bottom surface 22a. In the tire 2, generation of air column resonance is suppressed.

  In the tire 2, the first layer 46 is located on the radially inner side of the land portion tread surface 26. The loss tangent tan δ1 of the first layer 46 is small. The first layer 46 contributes to suppression of energy loss. Although the tire 2 includes the second layer 48, an increase in rolling resistance is suppressed.

  Further, in the tire 2, the first layers 46 and the second layers 48 having different loss tangent values are alternately arranged in the axial direction. The first layer 46 and the second layer 48 are laminated outside the reinforcing layer 44. Thereby, the vibration of the belt 14 (reinforcing layer 44) is suppressed.

  The tire 2 having a small ratio tan δ1 / tan δ2 between the loss tangent tan δ1 and the loss tangent tan δ2 has a large vibration suppressing effect. From this viewpoint, the ratio tan δ1 / tan δ2 is preferably 0.8 or less, more preferably 0.7 or less, and particularly preferably 0.6 or less.

  On the other hand, in a tire having a ratio tan δ1 / tan δ2 close to 1.0, the adhesion between the first layer 46 and the second layer 48 is excellent. Generation of peeling between the first layer 46 and the second layer 48 is suppressed. From this viewpoint, the ratio tan δ1 / tan δ2 is preferably 0.4 or more.

  Since the first layer 46 has a small loss tangent tan δ1, the vibration of the belt 14 is easily transmitted. The axial width of the first layer 46 is gradually reduced from the radially outer side to the inner side. The axial width of the second layer 48 is gradually increased from the radially outer side toward the inner side. A width Wb between the first layer 46 and the reinforcing layer 44 is reduced. Furthermore, the distance from the position where the first layer 46 and the reinforcing layer 44 are in contact to the bottom surface 22a of the main groove 22 is also increased. This further suppresses the vibration of the belt 14 from being transmitted to the bottom surface 22a.

  In the tire 2 having a small ratio D / Wb between the width Wb and the positional deviation D, the distance from the width Wb where the first layer 46 and the reinforcing layer 44 are in contact to the bottom surface 22a is increased. From this viewpoint, the ratio D / Wb is preferably small. The ratio D / Wb is preferably ¼ or less, more preferably ８ or less.

  The tread 4 needs to ensure sufficient rigidity from the viewpoint of handling stability. Ensuring this rigidity suppresses an increase in rolling resistance. For this reason, the width Wa of the first layer 46 is greater than or equal to the width Wt of the land portion tread surface 26. From the viewpoint of securing sufficient rigidity and reducing rolling resistance, it is preferable that the width Wa is larger than the width Wt.

  In the tire 2, the cross-sectional shape of the main groove 22 is narrowed from the outside in the radial direction toward the inside. The cross-sectional shape of the main groove 22 contributes to securing the rigidity of the block 24. The cross-sectional shape of the main groove 22 contributes to improvement in steering stability. In other words, by making the width Wa equal to or greater than the width Wt and further making the width Wa greater than the width Wt, the tire 2 is excellent in steering stability and further suppresses an increase in rolling resistance.

  By increasing the width of contact between the first layer 46 and the reinforcing layer 44, the rolling resistance is reduced. From this viewpoint, the ratio Wb / Wt between the width Wb and the width Wt is preferably 1/5 or more, and more preferably 1/3 or more.

  On the other hand, by reducing the width Wb of the first layer 46, the transmission of vibration to the bottom surface 22a is suppressed. From this viewpoint, the ratio Wb / Wt is preferably 2/5 or less, more preferably 1/3 or less, and particularly preferably 1/5 or less.

  In the tire 2, the thickness T1 of the first layer 46 is larger than the thickness Tg of the tread 4 on the bottom surface 22a. In the tire 2, the first layer 46 is located on the entire inner surface in the radial direction of the land portion tread 26. Thereby, the increase in rolling resistance is further suppressed.

  In the tire 2 in which the thickness T1 of the first layer 46 is thin, the cap layer 30 can be thickened. Exposure of the first layer 46 due to wear of the cap layer 30 is suppressed. Wear resistance and grip performance are maintained by the cap layer 30 being grounded. From this viewpoint, the thickness T1 is preferably 3 mm or less, and more preferably 2.5 mm or less.

  In the tire 2, the first layer 46 and the second layer 48 are in contact with the reinforcing layer 44, so that the vibration of the belt 14 is suppressed. If the thickness T1 of the first layer 46 is too small, the vibration suppressing effect cannot be obtained sufficiently. From the viewpoint of suppressing this vibration, the thickness T1 is preferably 2 mm or more, and more preferably 2.5 mm or more.

In the present invention, the loss tangent tan δ is measured in accordance with the provisions of “JIS K 6394”. The measurement conditions are as follows.
Viscoelastic spectrometer: "VESF-3" from Iwamoto Seisakusho
Initial strain: 10%
Dynamic strain: ± 1%
Frequency: 10Hz
Deformation mode: Tensile Measurement temperature: 70 ° C

  In the present invention, the size and angle of each member of the tire 2 are measured in a state where the tire 2 is incorporated in a regular rim and filled with air so as to have a regular internal pressure unless otherwise specified. At the time of measurement, no load is applied to the tire 2. In the present specification, the normal rim means a rim defined in a standard on which the tire 2 depends. “Standard rim” in the JATMA standard, “Design Rim” in the TRA standard, and “Measuring Rim” in the ETRTO standard are regular rims. In the present specification, the normal internal pressure means an internal pressure defined in a standard on which the tire 2 relies. “Maximum air pressure” in JATMA standard, “Maximum value” published in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in TRA standard, and “INFLATION PRESSURE” in ETRTO standard are normal internal pressures.

  Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be construed in a limited manner based on the description of the examples.

[Example 1]
A pneumatic tire having the basic structure shown in FIGS. 1 and 2 was obtained. The tire size was 225 / 40R18 88Y. In this tire, the tan δ1 of the first layer of the base layer, the tan δ2 of the second layer, and the ratio tan δ1 / tan δ2 are set as shown in Table 1. Table 1 shows the ratio Wb / Wt of the width Wb between the first layer and the reinforcing layer and the axial width Wt of the land tread surface. Table 1 shows the ratio D / Wb between the misalignment D between the center line of the land tread surface and the center line of the width Wb and the width Wb. The thickness T1 of the first layer was set as shown in Table 1.

[Comparative Examples 1 and 2]
A conventional pneumatic tire was prepared. Although not shown, in this tire, as shown in Table 1, the base layer was made of a single crosslinked rubber. Otherwise, a tire was obtained in the same manner as in Example 1.

[Comparative Example 3]
tan δ1 and tan δ2 were set as shown in Table 1. Otherwise, a tire was obtained in the same manner as in Example 1.

[Example 2-6]
tan δ2 was set as shown in Table 2. Otherwise, a tire was obtained in the same manner as in Example 1.

[Example 7-9]
The ratio Wb / Wt was set as shown in Table 3. Otherwise, a tire was obtained in the same manner as in Example 1.

[Examples 10-12]
T1 was set as shown in Table 4. Otherwise, a tire was obtained in the same manner as in Example 1.

[Examples 13 and 14]
The ratio D / Wb was set as shown in Table 4. Otherwise, a tire was obtained in the same manner as in Example 1.

[Vehicle noise]
Passage noise during actual coasting was measured. This measurement was carried out on an ISO road surface test course defined by ISO 10844 based on JASO C606. The evaluation results are shown in Tables 1 to 4. This evaluation result is obtained by comparing sound pressure values at a frequency of 800 Hz. In this evaluation result, the evaluation result of the tire of Comparative Example 2 is shown as 3.5 as a perfect score, and the evaluation results of other tires are shown as indexes. The evaluation result is preferably as the numerical value is larger.

[Rolling resistance]
These tires were subjected to a rolling resistance test in accordance with JIS D 4234 based on ISO 28580 using a rolling resistance tester. The rolling resistance coefficient was measured under the following measurement conditions.
Air pressure: 210kPa
Load: L. I. 80% of (road index)
Speed: 80km / h
The results are shown in Tables 1 to 4 as an index that sets Comparative Example 1 to 3.0 out of 5 points. The evaluation result is preferably as the numerical value is larger.

[High-speed stable performance]
These tires were incorporated into a regular rim 15 × 6JJ. The air pressure was set to 200 kPa. This tire was mounted on all wheels of a front-wheel drive vehicle having a displacement of 2000 cc (cm ² ). The driver drove the front-wheel drive car on a dry asphalt test course. The driver was driven at a speed of 120 km / h, and the high-speed stability performance was sensory evaluated. The results are shown in Tables 1 to 4 as indices with Comparative Example 1 as 5.0. The evaluation result is preferably as the numerical value is larger.

[durability]
A tire was incorporated into a regular rim, and the tire was filled with air. The tire was mounted on a drum type running test machine, and a longitudinal load was applied to run on the drum. After traveling a predetermined travel distance, the tire was dismantled. It was observed whether delamination occurred in the tread base layer. As for wear, it was observed whether or not the base layer was exposed on the tread surface. The results are shown in Tables 1 to 4 below.

  As shown in Tables 1 to 4, the tire of the example has a higher evaluation than the tire of the comparative example. From these evaluation results, the superiority of the present invention is clear.

  The invention described above can be widely applied to various tires having a main groove.

2 ... Tire 4 ... Tread 14 ... Belt 16 ... Band 20 ... Tread surface 22 ... Main groove 24 ... Block 26 ... Land tread surface 28 ... Base Layer 30 ... Cap layer 40 ... Inner layer 42 ... Outer layer 44 ... Reinforcing layer 46 ... First layer 48 ... Second layer

Claims (5)

A tread whose outer surface forms a tread surface, a pair of sidewalls each extending substantially inward in the radial direction from the end of the tread, a pair of beads each positioned radially inward of the sidewalls, and a tread and sidewalls A carcass stretched between one bead and the other bead along the inner side, and a reinforcing layer laminated with the carcass on the inner side in the radial direction of the tread,
A main groove extending in the circumferential direction is formed in the tread surface, and the tread surface is divided into main grooves and is composed of a land tread surface aligned in the axial direction,
The tread includes a base layer and a cap layer laminated on the outer side in the radial direction of the base layer,
This base layer is composed of a first layer located radially inside the land tread surface and a second layer located radially inside the main groove,
The axial width of the first layer is reduced from the radially outer side to the inner side, the first layer is in contact with the reinforcing layer,
The axial width of the second layer is increased from the radially outer side to the inner side, the second layer is in contact with the reinforcing layer and constitutes the bottom surface of the main groove,
The axial width Wa on the radially outer side of the first layer is not less than the axial width Wt of the land tread surface located on the radially outer side,
A pneumatic tire in which the loss tangent tan δ1 of the first layer is smaller than the loss tangent tan δ2 of the second layer.   The ratio Wb / Wt of the axial width Wb between the first layer and the reinforcing layer and the axial width Wt of the land tread surface is set to 1/5 or more and 1/3 or less. The described tire.   The tire according to claim 1 or 2, wherein the thickness T1 of the first layer is larger than the thickness Tg of the tread at the bottom of the main groove.   The tire according to claim 3, wherein a thickness T1 of the first layer is 2 mm or more and 3 mm or less.   The tire according to any one of claims 1 to 4, wherein a ratio tan δ1 / tan δ2 between the loss tangent tan δ1 of the first layer and the loss tangent tan δ2 of the second layer is 0.4 or more and 0.8 or less.

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