The circumferential groove and the circumferential groove of the pneumatic tire are formed inside than a tire equatorial line when mounted to the vehicle. In an outside center land portion and an inside center land portion, linear width direction sipes, width direction sipes and width direction sipes inclined with respect to the tire width direction are formed along the tire width direction. An inside shoulder land portion has a slick portion in which the surface of the inside shoulder land portion is slick in a grounding region of the inside shoulder land portion in a state where normal load is loaded on a tire.

TECHNICAL FIELD

The present invention relates to a tire, and more particularly to an ultra-high performance tire mounted on a vehicle capable of traveling at an ultra-high speed.

BACKGROUND ART

Conventionally, in an ultra-high performance tire mounted on a vehicle capable of traveling at an ultra-high speed exceeding 250 km/h, it is important to ensure high-speed durability and steering stability. There is known an ultra-high performance tire that reduces tire noise (specifically, road noise) while securing such high-speed durability and steering stability (Patent Literature 1).

The ultra-high performance tire is provided with a circumferential belt using a steel cord. Thus, the suppression of creep deformation and the improvement of rigidity in the tire circumferential direction are realized. In particular, by improving the rigidity in the tire circumferential direction, high frequency road noise during high-speed traveling can be suppressed.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

In recent years, there has been an increasing demand for environmental performance, such as further reduction of tire noise, even for the ultra-high performance tires described above. In particular, the value of the tire noise (also referred to as pass-by noise (PBN)) produced when the power source (engine) of the vehicle is stopped and the vehicle is coasting at the specified speed is uniformly specified to be not more than 74 dB (for normal road) for tires having a tire width of more than 275 mm (ECE R 117-02).

On the other hand, the performance of the vehicle is remarkably improved, and it is required to ensure rigidity for a large lateral force in order to cope with not only the maximum speed but also a high cornering speed.

Accordingly, the present invention has been made in view of such a situation, and an object of the present invention is to provide a tire capable of achieving both suppression of tire noise and high rigidity with respect to lateral force, while allowing the vehicle to travel at an ultra-high speed.

One aspect of the present invention is a tire (pneumatic tire10) having a tread portion (tread portion20) in which a plurality of linear circumferential grooves extending in tire circumferential direction are formed. The circumferential grooves include a first circumferential groove (circumferential groove31), a second circumferential groove (circumferential groove32) formed in inside when mounted to a vehicle than the first circumferential groove, and a third circumferential groove (circumferential groove33) formed in inside when mounted to the vehicle than the second circumferential groove, the second circumferential groove and the third circumferential groove are formed in inside when mounted to the vehicle than a tire equatorial line (tire equatorial line CL). The tread portion is provided with an outside center land portion (outside center land portion40) provided between the first circumferential groove and the second circumferential groove, an inside center land portion (inside center land portion50) provided between the second circumferential groove and the third circumferential groove, an inside shoulder land portion (inside shoulder land portion60) formed in inside when mounted to the vehicle than the third circumferential groove. A plurality of linear width direction sipes (width direction sipe41, width direction sipe51, and width direction sipe52) inclined with respect to the tire width direction along the tire width direction are formed in the outside center land portion and the inside center land portion, and the inside shoulder land portion has an inside slick portion (slick portion60a) in which a surface of the inside shoulder land portion is slick in a grounding region of the inside shoulder land portion in a state where normal load is loaded on the tire.

Effect of the Invention

According to the tire described above, it is possible to achieve both the suppression of tire noise and the high rigidity with respect to lateral force while allowing the vehicle to travel at an ultra-high speed.

DESCRIPTION OF EMBODIMENTS

Embodiments will be described below with reference to the drawings. Note that the same functions and structures are denoted by the same or similar reference numerals, and the description thereof is omitted as appropriate.

(1) Overall Schematic Configuration of the Tire

FIG. 1is a partial plan view of a tread of a pneumatic tire10according to the present embodiment. As shown inFIG. 1, a pattern (tread pattern) is formed in a tread portion20of the pneumatic tire10in consideration of various performances required for the pneumatic tire10, specifically, high-speed durability, vehicle dynamics (cornering performance, steering stability, braking performance, etc.), drainage performance, wear resistance, rolling resistance (RR), quietness (tire noise), and the like.

The pneumatic tire10is a so-called ultra high performance (UHP) tire, and can be suitably used for a vehicle capable of traveling at such an ultra high speed that the traveling speed exceeds 250 km/h.

Specifically, the pneumatic tire10may correspond to a speed symbol W (270 km/h), Y (300 km/h) or (Y) (greater than 300 km/h) or a speed category ZR (greater than 240 km/h). A speed symbol is a symbol representing the maximum speed at which a tire can run under prescribed conditions with the mass indicated by its load index.

The pneumatic tire10may not necessarily correspond to such a high maximum speed, and may correspond to, for example, the speed symbol V (240 km/h).

The size (rim diameter, tire width and aspect ratio) of the pneumatic tire10may be appropriately set according to the vehicle to be mounted, and is not particularly limited, but a rim diameter of 19 inches or more, a tire width of 275 mm or more, and an aspect ratio of 40% or less are assumed. However, smaller rim diameters (for example, 17 inches), narrower tire widths (for example, 215 mm) and higher aspect ratio (for example, 45%) may be used.

The tire width is also referred to as the section width. The section width is the total width of the tire excluding the patterns and characters on the sides of the tire, and does not include rim guards.

The pneumatic tire10can cope with running not only on a general road but also on a circuit (race course, race track). The pneumatic tire10also corresponds to wet weather, that is, wet road surface. The pneumatic tire10has sufficient rigidity for a large lateral force, especially to accommodate high cornering speed during circuit driving.

From such a viewpoint, in the pneumatic tire10, only a minimum number of groove elements (including sipes) for ensuring drainability are formed. Thus, the rigidity of the land portion is enhanced, and vehicle dynamics and wear resistance performance can be improved.

The pneumatic tire10clears the regulation value of the tire sole noise regulation international standard, specifically, ECE R 117-02. ECE R 117-02 specifies that the tire noise (also referred to as pass-by noise (PBN)) produced when the vehicle power source (engine) is stopped and the vehicle coasts at the specified speed shall be uniformly 74 dB or less (for normal load) for tires with a tire width exceeding 275 mm. In the case of an extra load, 75 dB or less is specified.

Therefore, the pneumatic tire10may have a narrower tire width as described above, but is assumed to have a tire width exceeding 275 mm which makes it more difficult to clear the specified PBN.

The pneumatic tire10has a so-called asymmetric pattern, and a surface (tire side part) to be an outside (or inside) when the tire is mounted to the vehicle is designated. For the pneumatic tire10, it is not necessary to specify the rotational direction when the vehicle is mounted.

As shown inFIG. 1, the pneumatic tire10has the tread portion20. The tread portion20is a part in contact with the road surface.

A plurality of linear circumferential grooves extending in the tire circumferential direction are formed in the tread portion20. Specifically, a circumferential groove31, a circumferential groove32and a circumferential groove33are formed in the tread portion20.

The circumferential groove31is formed most in outside when mounted to the vehicle. The circumferential groove31is formed outside than a tire equatorial line CL when mounted to the vehicle. In this embodiment, the circumferential groove31constitutes a first circumferential groove.

The circumferential groove32is formed between the circumferential groove31and the circumferential groove33in the tire width direction. The circumferential groove32is formed inside than the circumferential groove31when mounted to the vehicle. In this embodiment, the circumferential groove32forms a second circumferential groove.

The circumferential groove33is formed most in inside when mounted to the vehicle. That is, the circumferential groove33is formed in inside than the circumferential groove32when mounted to the vehicle. In this embodiment, the circumferential groove33constitutes a third circumferential groove.

The circumferential groove32and the circumferential groove33are formed inside than the tire equatorial line CL when mounted to the vehicle.

The tread portion20divided by the plurality of circumferential grooves has a plurality of land portions in contact with the road surface.

Specifically, the tread portion20includes an outside center land portion40, an inside center land portion50, an inside shoulder land portion60, and an outside shoulder land portion70.

The outside center land portion40is provided between the circumferential groove31and the circumferential groove32in the tire width direction. The outside center land portion40is a rib-like land portion continuous in the tire circumferential direction.

The inside center land portion50is provided between the circumferential groove32and the circumferential groove33in the tire width direction. The inside center land portion50is also a rib-like land portion continuous in the tire circumferential direction.

The inside shoulder land portion60is formed in a shoulder portion of inside when mounted to the vehicle. The inside shoulder land portion60is formed in inside than the circumferential groove33when mounted to the vehicle.

The outside shoulder land portion70is formed in a shoulder portion of outside when mounted to the vehicle. The outside shoulder land portion70is formed in outside than the circumferential groove31when mounted to the vehicle.

A plurality of width direction sipes41are formed in the outside center land portion40. The width direction sipes41are formed at a certain distance in the tire circumferential direction.

The width direction sipe41is a linear sipe extending in the tire width direction. One end of the width direction sipe41terminates within the outside center land portion40. The other end of the width direction sipe41communicates with the circumferential groove32.

The sipe is a narrow groove that closes within the ground plane of the tread portion20, and the opening width of the sipe at the time of non-grounding is not particularly limited, but is preferably 0.1 mm to 1.5 mm.

A plurality of width direction sipes51and width direction sipes52are formed in the inside center land portion50. A plurality of width direction sipes51and52are formed at a certain distance in the tire circumferential direction.

The width direction sipe51is formed near the circumferential groove32, and one end of the width direction sipe51terminates in the inside center land portion50. The width direction sipe52is formed near the circumferential groove33, and one end of the width direction sipe52terminates in the inside center land portion50.

The other end of the width direction sipe41communicates with the circumferential groove32, and the other end of the width direction sipe52communicates with the circumferential groove33.

In the present embodiment, the width direction sipe41, the width direction sipe51, and the width direction sipe52have similar shapes. The width direction sipe41, the width direction sipe51and the width direction sipe52are inclined to the tire width direction along the tire width direction. That is, the width direction sipe41, the width direction sipe51, and the width direction sipe52are not parallel to the tire width direction and are inclined to the tire width direction. The inclination angle of the width direction sipe41, the width direction sipe51, and the width direction sipe52with respect to the tire width direction is preferably 45 degrees or less, and is preferably 30 degrees or less in consideration of compatibility between rigidity of the land portion and PBN suppression.

In the present embodiment, the width direction sipes41, the width direction sipes51, and the width direction sipes52are inclined in the same direction, but it is not necessary that all the width direction sipes are inclined in the same direction. Further, the width direction sipe41, the width direction sipe51and the width direction sipe52are preferably offset from each other in the tire circumferential direction.

The inside shoulder land portion60has a slick portion60a. A plurality of shoulder grooves61terminating in the inside shoulder land portion60are formed in the inside shoulder land portion60. The shoulder grooves61are formed at a certain distance in the tire circumferential direction.

The slick portion60ais a portion having a slick-like surface of the inside shoulder land portion60. In this embodiment, the slick portion60aconstitutes an inside slick portion.

The slick shape means that groove elements such as a width direction groove and a circumferential groove are not formed. It should be noted that a pinhole-like recess which can be used for determining the wear amount of the tread portion20or a protrusion such as a spew formed for the purpose of preventing air accumulation during tire vulcanization may be formed.

The slick portion60amay be defined as a portion in which the surface of the shoulder land portion60when normal load is loaded to the pneumatic tire10is slick in the ground contacting area (grounding region) of the inside shoulder land portion60.

When normal load is loaded on the pneumatic tire10, the ground contacting area CA contacts the road surface. As shown inFIG. 1, no shoulder groove61is formed in the slick portion60aof the inside shoulder land portion60.

In Japan, normal internal pressure is the air pressure corresponding to the maximum load capacity of JATMA (Japan Automobile Tire Manufacturers Association) YearBook, and normal load is the maximum load capacity (maximum load) corresponding to the maximum load capacity of JATMA YearBook. In addition, ETRTO in Europe, TRA in the United States, and other tire standards in other countries are applicable.

Although the shoulder groove61is not formed in the ground contacting area CA, the area of the inside shoulder land portion60where the shoulder groove61is formed can also be grounded to the road surface during cornering or the like. The shoulder groove61may also serve as a treadwear indicator (slip sign) used to confirm the wear condition of the inside shoulder land portion60. The shoulder groove61may be formed for improving the grounding property of the inside shoulder land portion60.

The outside center land portion40has a slick portion40a. The slick portion40ais a portion having a slick-like surface of the outside center land portion40. The slick portion40ais formed in the region of outside when mounted to the vehicle in the outside center land portion40. That is, the slick portion40amay be defined as a portion where the surface of the outside center land portion40is slick in the region of outside when mounted to the vehicle in the outside center land portion40. In this embodiment, the slick portion40aconstitutes a center slick portion.

The outside shoulder land portion70has a slick portion70a. The slick portion70ais a portion having has a slick-like surface of the outside shoulder land portion70. The slick portion70ais formed in the region of outside when mounted to the vehicle in the inside shoulder land portion70. That is, the slick portion70amay be defined as a portion where the surface of the outside shoulder land portion70is slick in the region of inside when mounted to the vehicle in the outside shoulder land portion70. In this embodiment, the slick portion70aconstitutes an outside slick portion.

A plurality of lug grooves71are formed in the outside shoulder land portion70. A plurality of lug grooves71are formed at a certain distance in the tire circumferential direction.

The lug groove71is inclined to the tire width direction along the tire width direction. That is, the lug groove71is not parallel to the tire width direction but inclined to the tire width direction. The inclination angle of the lug groove71with respect to the tire width direction is preferably 45 degrees or less in the same manner as the width direction sipe41, the width direction sipe51, and the width direction sipe52, and is preferably 30 degrees or less in consideration of compatibility between rigidity of outside shoulder land portion70and PBN suppression.

In this embodiment, the sum of the groove widths of the circumferential groove31, the circumferential groove32, and the circumferential groove33is larger than the width of the outside center land portion40along the tire width direction.

The sum of the groove widths of the circumferential groove31, the circumferential groove32and the circumferential groove33is wider than the width of inside center land portion50along the tire width direction.

On the other hand, the sum of the groove widths of the circumferential groove31, the circumferential groove32and the circumferential groove33is narrower than the width of the slick portion40a, the slick portion60aand the slick portion70aalong the tire width direction.

In the present embodiment, the width of the slick portion40aalong the tire width direction is larger than the width of the outside center land portion40other than the slick portion40aalong the tire width direction, that is, the width of the portion where the width direction sipe41is formed along the tire width direction.

In this embodiment, the width of the lug groove71in the ground contacting area CA along the tire width direction is larger than the width of the slick portion70aalong the tire width direction.

(2) Cross-Sectional Shape of the Circumferential Groove

Next, the cross-sectional shapes of the circumferential groove31, the circumferential groove32, and the circumferential groove33will be described.FIG. 2is a schematic cross-sectional view of the pneumatic tire10along the tire width direction and the tire radial direction. InFIG. 2, hatching of a cross section and a structure such as a carcass and a belt are omitted.

As shown inFIG. 2, the outside shoulder land portion70has a groove wall portion75forming the circumferential groove31. In this embodiment, the groove wall portion75constitutes a first groove wall portion.

The outside center land portion40has a groove wall portion45forming the circumferential groove32. In this embodiment, the groove wall portion45constitutes a second groove wall portion.

The inside center land portion50has a groove wall portion55forming the circumferential groove33. In this embodiment, the groove wall portion55constitutes a third groove wall portion.

The groove wall portion75, the groove wall portion45and the groove wall portion55incline toward inside in the tire radial direction to approach inside when mounted to the vehicle. In this embodiment, the sectional shapes of the groove wall portion75, the groove wall portion45, and the groove wall portion55are linear. However, the entire groove wall portion may not necessarily be in a linear shape inclined toward inside the tire radial direction to approach inside when mounted to the vehicle.

In this embodiment, the groove depths of the circumferential groove31, the circumferential groove32and the circumferential groove33are the same.

The groove wall portion75is inclined more than the groove wall portion45. The groove wall portion45is inclined more than the groove wall portion55.

That is, the inclination angle of the groove wall portion75with respect to the tire radial direction is larger than the inclination angle of the groove wall portion45with respect to the tire radial direction, and the inclination angle of the groove wall portion45with respect to the tire radial direction is larger than the inclination angle of the groove wall portion55with respect to the tire radial direction. Therefore, the relation of the inclination angle is the groove wall portion75>the groove wall portion45>the groove wall portion55.

(3) Shape of Width Direction Sipe

FIG. 3is a plan view of the width direction sipe52. The width direction sipe41and the width direction sipe51have the same shape.

As shown inFIG. 3, the width direction sipe52includes a width direction groove wall portion521, a width direction groove wall portion522, and a circumferential groove wall portion523.

The width direction groove wall portion521extends in the tire width direction. In this embodiment, the width direction groove wall portion521constitutes a first width direction groove wall portion.

The width direction groove wall portion522extends in the tire width direction like the width direction groove wall portion521and extends to the center side of the inside center land portion50from the width direction groove wall portion521. In this embodiment, the width direction groove wall portion522constitutes a second width direction groove wall portion. In the case of the width direction sipe41, the width direction groove wall portion522extends to the center side of the outside center land portion40.

The circumferential groove wall portion523is communicated to the width direction groove wall portion521and the width direction groove wall portion522. The circumferential groove wall portion523is linear.

Since the width direction groove wall portion521and the width direction groove wall portion522are different in length, the circumferential groove wall portion523is inclined with respect to the tire circumferential direction and also inclined with respect to the tire width direction. That is, one end of the width direction sipe52has a shape like a tip of a sword in a tread surface view.

An inclined portion524inclined toward inside in the tire radial direction from the tread surface (portion in contact with the road surface) side of the center land portion50is formed at a peripheral edge portion of the width direction sipe52.

The inclined portion524communicates to a sipe portion525of the width direction sipe52. The sipe part525is linear along the tire width direction, but may not necessarily be linear in tire radial direction, that is, the sipe depth direction. For example, the sipe portion525may have a shape that zigzags in the tire circumferential direction as it goes to inside in the tire radial direction. More specifically, the sipe portion525may be a so-called three-dimensional sipe having an M-shaped cross-sectional shape along the tire circumferential direction and the tire radial direction.

(4) Shape of Lug Groove

FIG. 4is a plan view of the lug groove71. As shown inFIG. 4, the lug groove71is formed by an inclined portion711, a groove portion712, an end portion713, and an end portion714. In this embodiment, the lug groove71has a slightly curved wedge-shape.

The inclined portion711is formed at the peripheral edge portion of the lug groove71. The inclined portion711is inclined toward inside in the tire radial direction from the tread surface side of the outside shoulder land portion70. The inclined portion711communicates to the groove portion712.

The groove portion712is a void having a certain depth in the tire radial direction. The depth of the groove portion712is not particularly limited, but is set to an appropriate value in consideration of drainability, grounding property (rigidity) of the outside shoulder land portion70, and PBN suppression.

The end portion713is an end portion of the lug groove71located in outside when mounted to the vehicle. The end portion714is an end portion of the lug groove71located in inside when mounted to the vehicle. The end portion713and the end portion714are offset in the tire circumferential direction, that is, their positions in the tire circumferential direction are different.

(5) Function and Effects

According to the above-described embodiment, the following effects can be obtained. More specifically, three circumferential grooves (circumferential groove31, circumferential groove32, and circumferential groove33) are formed in the tread portion20of the pneumatic tire10, and the outside center land portion40, the inside center land portion50, and the inside shoulder land portion60which are divided by the circumferential grooves are provided.

The plurality of width direction sipes (width direction sipe41, width direction sipe51, and width direction sipe52) are formed in the outside center land portion40and the inside center land portion50.

Firstly, the three circumferential grooves ensure the drainability necessary for travelling a vehicle mounted with an ultra-high performance tire such as the pneumatic tire10. Further, since the circumferential groove32and the circumferential groove33are formed in inside when mounted to the vehicle than the tire equatorial line CL, and the width direction sipe41, the width direction sipe51and the width direction sipe52are formed in inside when mounted to the vehicle than the tire equatorial line CL, the drainability of inside of the tread portion20on the basis of the tire equatorial line CL when mounted to the vehicle can be enhanced.

In addition, the inside shoulder land portion60has the slick portion60an which the surface of the shoulder land portion60when normal load is loaded to the pneumatic tire10is slick in the ground contacting area of the inside shoulder land portion60.

Therefore, the slick portion60acan be located in the ground contacting area CA of the inside of the tread portion20on the basis of the tire equatorial line CL when mounted to the vehicle. Since the slick portion60adoes not have a groove element, the rigidity of the inside shoulder land portion60, in particular, the rigidity with respect to lateral force, can be improved. Furthermore, since the slick portion60ahas no groove element, it contributes to the suppression of tire noise, specifically, pass-by noise (PBN).

That is, the pneumatic tire10can achieve both the suppression of tire noise and the high rigidity with respect to lateral force, while allowing the vehicle to travel at an ultrafast speed including a wet road surface.

In this embodiment, the outside center land portion40has the slick portion40ain which the surface of the outside center land portion40is slick in the region of outside in the outside center land portion40when mounted to the vehicle. Therefore, the slick portion40acan be located in the ground contacting area CA of the outside of the tread portion20on the basis of the tire equatorial line CL when mounted to the vehicle. Since the slick portion40ahas no groove element, the rigidity of the outside center land portion40, in particular, the rigidity with respect to lateral force, can be improved. Further, since the slick portion40ahas no groove element, it contributes to the suppression of the PBN. Thus, the suppression of tire noise and the high rigidity with respect to lateral force can be made compatible in a higher dimension.

In this embodiment, the outside shoulder land portion70has a slick portion70ain which the surface of the outside shoulder land portion70is slick in the region of inside in the outside shoulder land portion70when mounted to the vehicle. Therefore, the slick portion70acan be located in the ground contacting area CA of the outside of the tread portion20on the basis of the tire equatorial line CL when mounted to the vehicle. Since the slick portion70ahas no groove element, the rigidity of outside center land portion40, in particular, the rigidity with respect to lateral force, can be improved. Further, since the slick portion40ahas no groove element, it contributes to the suppression of the PBN. Thus, the suppression of tire noise and the high rigidity with respect to lateral force can be made compatible in a higher dimension.

Further, by providing the slick portion60a, the slick portion40a, and the slick portion70afrom inside to outside when mounted to the vehicle, the grip, particularly on the dry road surface, can be effectively improved.

In this embodiment, the plurality of lug grooves71inclined with respect to the tire width direction are formed along the tire width direction in the outside shoulder land portion70. Since the lug groove71is inclined with respect to the tire width direction along the tire width direction, the lug groove71contributes to the improvement of the drainability without greatly reducing the rigidity of the outside shoulder land portion70. If the lug groove71is largely inclined with respect to the tire width direction, the rigidity of the outside shoulder land portion70is greatly reduced and is not preferable.

Since the lug groove71is not parallel to the tire width direction, tire noise generated when the lug groove71comes into contact with the road surface can also be suppressed. Further, by forming the lug groove71, the outside shoulder land portion70around the lug groove71is easily deformed, and the grounding property of the outside shoulder land portion70located in the ground contacting area CA is improved. This can further improve the grip, especially on the dry road surface.

In the present embodiment, the width direction sipe52(also the width direction sipe41and the width direction sipe51) is formed by the width direction groove wall portion521extending in the tire width direction, the width direction groove wall portion522extending in the tire width direction and extending from the width direction groove wall portion521to the center side of the inside center land portion50, and the linear circumferential groove wall portion523communicating to the width direction groove wall portion521and the width direction groove wall portion522.

For this reason, one end (which may be referred to as the tip) of the width direction sipe52is communicated in such a state that the circumferential groove wall portion523is inclined rather than perpendicular to the width direction groove wall portion521and the width direction groove wall portion522, and is shaped like the tip of a sword. As a result, it is possible to suppress the occurrence of cracks starting at a position where the circumferential groove wall523is communicated to the widthwise groove wall521and the widthwise groove wall522.

In this embodiment, the outside shoulder land portion70has the groove wall portion75, the outside center land portion40has the groove wall portion45, and the inside center land portion50has the groove wall portion55.

The groove wall portion75, the groove wall portion45, and the groove wall portion55are inclined toward inside in the tire radial direction to approach inside when mounted to the vehicle, and the groove wall portion75is inclined more than the groove wall portion45. Therefore, the groove wall portion75contributes to increase the rigidity with respect to the input of lateral force from outside to the outside shoulder land portion70when mounted to the vehicle.

Further, in the present embodiment, the groove wall portion45is inclined more than the groove wall portion55. Therefore, the groove wall portion45can achieve a certain degree of rigidity improvement with respect to the input of lateral force from outside to the outside center land portion40when mounted to the vehicle, while securing the drainability.

In this embodiment, the slick portion70ais located within the ground contacting area CA. Further, the width of the lug groove71in the ground contacting area CA along the tire width direction is wider than the width of the slick portion70aalong the tire width direction. Thus, while the grip of the slick portion70aon the dry road surface is secured, the drainability in the ground contacting area of the outside shoulder land portion70can be secured, and in particular, it can contribute to the improvement of vehicle dynamics on the wet road surface.

In this embodiment, the sum of the groove widths of the circumferential groove31, the circumferential groove32, and the circumferential groove33is larger than the width of outside center land portion40along the tire width direction. The sum of the groove widths of the circumferential groove31, the circumferential groove32and the circumferential groove33is wider than the width of the inside center land portion50along the tire width direction.

On the other hand, the sum of the groove widths of the circumferential groove31, the circumferential groove32and the circumferential groove33is narrower than the width of the slick portion40a, the slick portion60aand the slick portion70aalong the tire width direction.

Thus, the plurality of slick portions in the ground contacting area CA can achieve a high degree of rigidity improvement with respect to lateral force and PBN suppression while surely securing the drainability necessary for the traveling of the vehicle mounted with the ultra-high performance tire such as the pneumatic tire10.

(6) Other Embodiments

Although the contents of the present invention have been described above in accordance with the embodiments, the present invention is not limited to these descriptions, and it is obvious to those skilled in the art that various modifications and improvements are possible.

For example, in the pneumatic tire10, three circumferential grooves are formed in the tread portion20, but four or more circumferential grooves may be formed in the tread portion20. The circumferential groove to be added may be a circumferential narrow groove narrower than the width of the circumferential groove31, the circumferential groove32and the circumferential groove33.

In the pneumatic tire10, the circumferential groove31, the circumferential groove32, and the circumferential groove33are perfectly linear, but may be formed so as to meander a little in the tire width direction as long as the entire circumferential groove extends in the tire circumferential direction.

In the pneumatic tire10, the sum of the groove widths of the circumferential groove31, the circumferential groove32and the circumferential groove33is wider than the width of the outside center land portion40along the tire width direction, and the sum of the groove widths of the circumferential groove31, the circumferential groove32and the circumferential groove33is wider than the width of the inside center land portion50along the tire width direction, but either or both of these relationships may not be satisfied.

In the pneumatic tire10, the sum of the groove widths of the circumferential groove31, the circumferential groove32, and the circumferential groove33is smaller than the widths of the slick portion40a, the slick portion60a, and the slick portion70aalong the tire width direction, but such a relationship may not be satisfied.

Part of the land portion and the groove elements (including sipes) constituting the pneumatic tire10may not necessarily be as shown inFIG. 1˜4.

As noted above, embodiments of the invention have been described, but it should not be understood that the statements and drawings that make up part of this disclosure limit the invention. Various alternative embodiments, embodiments and operational techniques will become apparent to those skilled in the art from this disclosure.

REFERENCE SIGNS LIST