A tire comprises a tread portion 2. The tread portion 2 comprises a plurality of first oblique grooves 10A extending obliquely from a first tread edge Te1 positioned on one side in a tire axial direction toward a tire equator C. Each of the first oblique grooves 10A comprises a main body portion 12 extending from the first tread edge Te1 without reaching the tire equator C and a branch portion 13 branching off from the main body portion 12 and extending to cross the tire equator. The branch portion 13 terminates without being connected with other grooves than the first oblique grooves 10A.

TECHNICAL FIELD

The present invention relates to a tire capable of exerting excellent on-snow performance while maintaining steering stability on a dry road surface.

BACKGROUND ART

For example, Japanese Unexamined Patent Application No. 2016-196288 (Patent Literature 1) proposed a winter tire. The tread portion of the tire disclosed in Patent Literature 1 is provided with a plurality of oblique grooves extending obliquely from one of tread edges toward a tire equator. Each of the oblique grooves disclosed in Patent Literature 1 includes a main body portion extending from one of the tread edges without reaching the tire equator and a branch portion branching off from the main body portion and extending to cross the tire equator.

However, the branch portion disclosed in Patent Literature 1 is connected with another one of the oblique grooves extending from the other one of the tread edges. The branch portions configured as such decrease rigidity of a land region in the vicinity of the tire equator, therefore, it is possible that the steering stability on a dry road surface eventually decreases.

SUMMARY OF THE INVENTION

The present invention was made in view of the above, and a primary object thereof is to provide a tire capable of exerting excellent on-snow performance while maintaining the steering stability on a dry road surface.

In one aspect of the present invention, a tire comprises a tread portion comprising a plurality of first oblique grooves extending obliquely from a first tread edge positioned on one side in a tire axial direction toward a tire equator, wherein each of the first oblique grooves comprises a main body portion extending from the first tread edge without reaching the tire equator and a branch portion branching off from the main body portion and extending to cross the tire equator, and the branch portion terminates without being connected with other grooves than the first oblique grooves.

In another aspect of the invention, it is preferred that the tread portion further comprises a plurality of second oblique grooves extending from a second tread edge positioned on the other side in the tire axial direction toward the tire equator, the branch portion terminates before reaching the second oblique grooves, and a width of a spacing portion between an end portion of the branch portion and its adjacent one of the second oblique grooves is smaller than a groove width of the branch portion.

In another aspect of the invention, it is preferred that the spacing portion is provided with a sipe connecting between the branch portion and its adjacent one of the second oblique grooves and having a width less than 1.5 mm.

In another aspect of the invention, it is preferred that the tread portion further comprises a center land region, and the center land region extends continuously in a tire circumferential direction without being divided by a groove having a width more than 1.5 mm.

In another aspect of the invention, it is preferred that the main body portion comprises a tip portion terminating before reaching the tire equator, a tapered land region is defined at a corner portion located between the tip portion and the branch portion, and the tapered land region has a chamfered portion inclined inwardly in a tire radial direction toward the corner portion.

In another aspect of the invention, it is preferred that in a cross section of the tire passing through a rotational axis thereof, the tread portion comprises a ground contacting surface and buttress surfaces disposed on both outer sides in the tire axial direction of the ground contacting surface, and the ground contacting surface and each of the buttress surfaces are connected by an arcuate surface having a radius of curvature in a range of from 1 to 10 mm.

In another aspect of the invention, it is preferred that the tread portion is provided with a longitudinal sipe extending in the tire circumferential direction from the branch portion.

In another aspect of the invention, it is preferred that the longitudinal sipe has one end connected to the branch portion and the other end terminating without being connected with any other grooves and sipes.

In another aspect of the invention, it is preferred that the longitudinal sipe has a length in the tire circumferential direction smaller than the groove width of the branch portion.

In another aspect of the invention, it is preferred that a tip of the main body portion is inclined at an angle in a range of from 70 to 80 degrees with respect to the tire axial direction.

In another aspect of the invention, it is preferred that the tread portion further comprises a shoulder block defined between the plurality of the first oblique grooves and arranged closest to the first tread edge, the shoulder block is provided with a longitudinal closed sipe which extends in the tire circumferential direction and has both ends terminating within the block.

DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of the present invention will now be described in detail.

FIG. 1is a development view of a tread portion2of a tire1in this embodiment. As shown inFIG. 1, the tire1in this embodiment is suitably used as a winter tire for a passenger car, for example. In another embodiment of the present invention, the tire1can be used as a pneumatic tire for heavy load, a non-pneumatic tire not filled with pressurized air inside the tire, or the like, for example.

The tire1in this embodiment is provided with a directional pattern in which a rotational direction R is specified, for example. The rotational direction R is indicated by letters or symbols on a sidewall portion (not shown).

The tire1in this embodiment is provided with the tread portion2positioned between a first tread edge Te1and a second tread edge Te2. The tread portion2includes a first tread portion2A positioned between a tire equator C and the first tread edge Te1and a second tread portion2B positioned between the tire equator C and the second tread edge Te2.

In a case of a pneumatic tire, the first tread edge Te1and the second tread edge Te2are defined as outermost ground contacting positions in the tire axial direction of the tire1when the tire1in a standard state is in contact with a flat surface with zero camber angle by being loaded with a standard tire load. The standard state is a state in which the tire is mounted on a standard rim, inflated to a standard pressure, and loaded with no tire load. In this specification, dimensions and the like of various parts of the tire are those measured under the standard state, unless otherwise noted.

The “standard rim” is a wheel rim specified for the concerned tire by a standard included in a standardization system on which the tire is based, for example, the “normal wheel rim” in JATMA, “Design Rim” in TRA, and “Measuring Rim” in ETRTO.

The “standard pressure” is air pressure specified for the concerned tire by a standard included in a standardization system on which the tire is based, for example, the “maximum air pressure” in JATMA, maximum value listed in the “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” table in TRA, and “INFLATION PRESSURE” in ETRTO.

The “standard load” is a tire load specified for the concerned tire by a standard included in a standardization system on which the tire is based, for example, the “maximum load capacity” in JATMA, maximum value listed in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” table in TRA, and “LOAD CAPACITY” in ETRTO.

The tread portion2is provided with a plurality of first oblique grooves10A and a plurality of second oblique grooves10B (hereinafter they may be simply referred to as “oblique grooves10”). The first oblique grooves10A extend obliquely from the first tread edge Te1toward the tire equator C. The second oblique grooves10B extends obliquely from the second tread edge Te2toward the tire equator C. The second oblique grooves10B has substantially the same configuration as the first oblique grooves10A. Thereby, unless otherwise noted, the configuration of the first oblique grooves10A can be applied to the second oblique grooves10B.

FIG. 2is an enlarged view of contours of the first oblique grooves10A. As shown inFIG. 2, each of the first oblique grooves10A includes a main body portion12and a branch portion13. The main body portion12extends from the first tread edge Te1without reaching the tire equator. The branch portion13branches off from the main body portion12and extends to cross the tire equator C. First oblique grooves10A forms long snow blocks extending obliquely with respect to a tire axial direction during running on a snowy road surface. In particular, during running on a snowy road surface, large ground contact pressure is applied to the branch portions13which cross the tire equator, therefore, harder snow blocks are formed. The first oblique grooves10A shear the snow blocks, therefore, it is possible that large on-snow traction is obtained.

It is preferred that each of the main body portions12is inclined toward heel-side in the rotational direction R from the first tread edge Te1to the tire equator C, for example. In a preferred embodiment, each of the main body portions12is curved such that an angle θ1thereof with respect to the tire axial direction gradually increases toward the tire equator C. It is preferred that the angle θ1is in a range of from 5 to 75 degrees, for example. The oblique grooves10configured as such can exert snow block shearing force also in the tire axial direction during running on a snowy road.

Each of the main body portions12includes a tip portion14which terminates before reaching the tire equator C, for example. It is preferred that a distance L1in the tire axial direction between an end of the tip portion14(that is, an end of a groove center line of the tip portion) and the tire equator is in a range of from 1.0% to 3.0% of a tread width TW (shown inFIG. 1, and the same applies hereinafter), for example. The tread width TW is a distance in the tire axial direction of the tire in the standard state between the first tread edge Te1and the second tread edge Te2.

It is preferred that each of the main body portions12has a groove width gradually increasing toward the first tread edge Te1, for example. It is preferred that a maximum groove width w1of each of the main body portion12is in a range of from 2.5% to 4.5% of the tread width TW, for example. In the case of a winter tire for a passenger car, a depth of each of the main body portions12is in a range of from 7.0 to 11.0 mm, preferably from 8.0 to 9.0 mm, for example.

Each of the branch portions13terminates without being connected with other grooves than the respective first oblique groove10A. Here, the “other grooves” means those having a width not less than 1.5 mm, and sipes having a width less than 1.5 mm are excluded. The branch portions13configured as such suppress decrease in the rigidity of a land region near the tire equator C while obtaining the on-snow traction as described above, therefore, it is possible that the steering stability on a dry road surface is maintained eventually.

FIG. 3is an enlarged view showing the tip portions14and the branch portions13of the oblique grooves10. As shown inFIG. 3, in this embodiment, the branch portions13of the first oblique grooves10A and the branch portions13of the second oblique grooves10B are arranged alternately in a tire circumferential direction. Each of the branch portions13of the first oblique grooves10A terminates before reaching its adjacent one of the second oblique grooves10B, for example. Each of the branch portions13of the second oblique grooves10B terminates before reaching its adjacent one of the first oblique grooves10A, for example.

In order to improve the on-snow traction and cornering performance on a snowy road surface in a good balance, it is preferred that each of the branch portions13is arranged at an angle82in a range of from 15 to 30 degrees with respect to the tire axial direction, for example. In a more preferred embodiment, it is preferred that, in each of the oblique grooves, an angle83between a groove centerline of the branch portion13and the groove centerline of the tip portion14is in a range of from 35 to 45 degrees, for example.

An intersection point of the groove center line of the main body portion12and an extension line of the groove center line of the branch portion13is defined as a first intersection point21. It is preferred that a distance L2in the tire axial direction between the first intersection point21and the tire equator C is in a range of from 3.0% to 5.0% of the tread width TW, for example. The branch portions13configured as such are useful for improving the steering stability on a dry road surface and the on-snow performance in a good balance.

From a similar point of view, it is preferred that each of the branch portions13has a groove width w2in a range of from 0.50 to 0.60 times the maximum groove width w1(shown inFIG. 2) of each of the main body portions12, for example.

It is preferred that, in each of the oblique grooves, the branch portion13has a smaller depth than the main body portion12, for example. Specifically, it is preferred that the depth of the branch portion13is in a range of from 5.0 to 10.0 mm, for example. The branch portions13configured as such are helpful for maintaining the steering stability on a dry road surface.

It is preferred that a width w3of each of spacing portions15between an end portion of each of the branch portions13and its adjacent one of the second oblique grooves10B is smaller than the groove width w2of each of the branch portions13, for example. Specifically, it is preferred that the width w3of each of the spacing portions15is in a range of from 0.70 to 0.90 times the groove width w2of each of the branch portions13, for example. Thereby, the spacing portions15are moderately deformed while obtaining the above-mentioned effects, therefore, clogging of snow in the branch portions13is suppressed during running on a snowy road.

In a more preferred embodiment, it is preferred that each of the spacing portions15is provided with a sipe16connecting between the branch portion13and its adjacent one of the second oblique grooves10B. Note that, in this specification, the term “sipe” means a cut or a slit having a width of less than 1.5 mm. It is possible that the sipes16suppress clogging of snow in the branch portions13during running on a snowy road. In an embodiment like this, as compared with an embodiment in which the branch portions13are connected with the second oblique grooves10B, it is possible that the on-snow performance is maintained over a long period of time.

For each of the oblique grooves, a tapered land region is defined at a corner portion17between the tip portion14and the branch portion13. It is preferred that each of the tapered land regions is provided with a chamfered portion18inclined inwardly in a tire radial direction toward its adjacent one of the corner portions17. It is preferred that each of the chamfered portions18is inclined at an angle (not shown) in a range of from 40 to 50 degrees with respect to the tire radial direction, for example. In this embodiment, owing to the configuration having the branch portions13terminating without being connected and the chamfered portions18, as compared with an embodiment in which the branch portions13are connected with the second oblique grooves10B, it is possible that uneven wear of the land region near the tire equator C is effectively suppressed.

As shown inFIG. 2, in a preferred embodiment, a plurality of joint grooves25each connecting between a pair of the oblique grooves10adjacent to each other in the tire circumferential direction are provided. It is preferred that each of the joint grooves25is inclined in the opposite direction to the oblique grooves10, for example. In other words, it is preferred that each of the joint grooves25is inclined toward the tire equator C in a direction opposite to the rotational direction R.

The joint grooves25include first joint grooves26and second joint grooves27, for example. The first joint grooves26are provided closest to the tire equator C among the plurality of the joint grooves25each arranged between adjacent oblique grooves10, for example. The second joint grooves27are arranged on an outer side in the tire axial direction of the first joint grooves26. The second joint grooves27in this embodiment are provided closest to the first tread edge Te1among the plurality of the joint grooves25, for example.

An intersection point of a groove center line of each of the oblique grooves10and an extension line of a groove center line of one of the first joint grooves26connected with the each of the oblique grooves10on the heel-side in the rotational direction R is defined as a second intersection point22. It is preferred that a distance L3in the tire axial direction between the tire equator C and each of the second intersection point22is in a range of from 0.08 to 0.12 times the tread width TW, for example.

It is preferred that each of the first joint grooves26is inclined at an angle θ4in a range of from 35 to 45 degrees with respect to the tire circumferential direction, for example. The first joint grooves26configured as such can provide the snow block shearing force in the tire circumferential direction and the tire axial direction in a good balance.

An intersection point of the groove center line of each of the oblique grooves10and an extension line of a groove center line of one of the second joint grooves27connected with the each of the oblique grooves10on the heel-side in the rotational direction R is defined as a third intersection point23. It is preferred that a distance L4in the tire axial direction between the tire equator C and each of the third intersection points23is in a range of from 0.22 to 0.35 times the tread width TW, for example.

It is preferred that each of the second joint grooves27is inclined at an angle θ5smaller than that of each of the first joint grooves26with respect to the tire circumferential direction, for example. Specifically, it is preferred that the angle θ5with respect to the tire circumferential direction of each of the second joint grooves27is in a range of from 20 to 30 degrees, for example. Thereby, the cornering performance on a snowy road surface is further improved.

As shown inFIG. 1, the tread portion2has a center land region5, middle block rows6, and shoulder block rows7by the above-described grooves provided therein, for example. The center land region5is provided at a center portion in the tire axial direction of the tread portion2. The center land region5in this embodiment is defined between the plurality of the first oblique grooves10A and the first joint grooves26connecting therebetween, the plurality of the second oblique grooves10B and the first joint grooves26connecting therebetween, for example.

It is preferred that the center land region5, due to the above-described branch portions13provided therein, extends continuously in the tire circumferential direction without being divided by a groove having a width more than 1.5 mm, for example. In the center land region5configured as such, excessive deformation thereof is suppressed, therefore, it is helpful for improving the steering stability on a dry road surface.

It is preferred that the center land region5is provided with a plurality of center sipes31extending in a zigzag manner in the tire axial direction, for example. The center sipes31configured as such can provide high traction by edges thereof on a road surface covered with strongly compacted snow (hereinafter may be referred to as “compacted snow road surface”), for example.

FIG. 4is an enlarged view of one of the middle block rows6and one of the shoulder block rows7. As shown inFIG. 4, in each of the middle block rows6, a plurality of middle blocks28are arranged in the tire circumferential direction. Each of the middle blocks28is defined between the first joint groove26and the second joint groove27between a pair of the oblique grooves adjacent to each other in the tire circumferential direction.

It is preferred that each of the middle blocks28is provided with a lateral groove32, for example. In each of the middle blocks28, one end32aof the lateral groove32is connected with one of the oblique grooves10positioned on a toe-side in the rotational direction R of the middle block28, for example. Further, the other end32bof the lateral groove32terminates within the middle block28. The lateral grooves32configured as such can improve the on-snow performance while maintaining the steering stability on a dry road surface by suppressing decrease in the rigidity of the middle blocks28.

It is preferred that each of the lateral grooves32extends so as to be smoothly connected with its adjacent one of the first joint grooves26with its adjacent one of the oblique grooves10therebetween, for example. The expression “smoothly connected” includes an embodiment in which an extension of the first joint groove26in a longitudinal direction thereof intersects with at least a part of an end portion on a side of the lateral groove32of the oblique groove10.

It is preferred that the lateral grooves32are inclined in the same direction as the first joint grooves26, for example. It is preferred that each of the lateral grooves32is inclined at an angle θ6in a range of from 30 to 50 degrees with respect to the tire circumferential direction, for example. The lateral grooves32configured as such promote deformation of the middle blocks28, therefore, it is possible that clogging of snow in the oblique grooves10and each of the joint grooves25is suppressed eventually.

As shown inFIG. 2, an intersection point of a groove center line of each of the lateral grooves32on a side of the one end32aand an extension line of the groove center line of its adjacent one of the oblique grooves10is defined as a fourth intersection point24. It is preferred that a distance L5in the tire axial direction between the tire equator C and each of the fourth intersection points24is in a range of from 0.15 to 0.20 times the tread width TW, for example.

As shown inFIG. 4, it is preferred that each of the middle blocks28is provided with a plurality of middle sipes33extending in a zigzag manner along the joint grooves25, for example. The middle sipes33configured as such can improve the traction and the cornering performance on a compacted snow road surface.

In each of the shoulder block rows7, a plurality of shoulder blocks29is arranged in the tire circumferential direction. Each of the shoulder blocks29is defined on an outer side in the tire axial direction of the second joint groove27between a pair of the oblique grooves10adjacent to each other in the tire circumferential direction.

It is preferred that each of the shoulder blocks29is provided with a plurality of shoulder sipes34that are inclined in the opposite direction to the middle sipes33and extend in a zigzag manner, for example. Thereby, the middle blocks28and the shoulder blocks29are easily deformed in different directions, therefore, clogging of snow in each of the grooves is suppressed eventually.

FIG. 5is an enlarged partial view of a cross section of the tire passing through a rotational axis thereof. As shown inFIG. 5, the tread portion2includes a ground contacting surface2sand buttress surfaces35disposed on both outer sides in the tire axial direction of the ground contacting surface. In a preferred embodiment, the ground contacting surface2sand each of the buttress surfaces35are connected by an arcuate surface36having a radius of curvature r1in a range of from 1 to 10 mm. Thereby, it is possible that a large area, which can contact with the ground, of the tread portion2is secured, therefore, it is possible that the cornering performance on a dry road surface and on an icy road surface is improved, for example.

As shown inFIG. 1, a land ratio Lr of the tread portion2in this embodiment is preferably not less than 60%, more preferably not less than 65%, and preferably not more than 80%, more preferably not more than 75%. Thereby, the steering stability on a dry road surface and the on-snow performance are improved in a good balance. In this specification, the term “land ratio” means a ratio Sb/Sa of a total area Sa of an imaginary ground contacting surface obtained by filling all the grooves and the sipes and the actual total ground contacting area Sb.

From the similar point of view, rubber hardness Ht of a tread rubber forming the tread portion2is preferably not less than 45 degrees, more preferably not less than 55 degrees, and preferably not more than 70 degrees, more preferably not more than 65 degrees. In this specification, the term “rubber hardness” means hardness measured by a type-A durometer under an environment of 23 degrees Celsius in accordance with Japanese Industrial Standard JIS-K 6253.

FIG. 7is a development view of the tread portion2of the tire1according to another embodiment of the present invention. InFIG. 7, the same reference numerals are given to the elements common to the above-described embodiment, and the explanation thereof is omitted here.

As shown inFIG. 7, the tread portion2in this embodiment is provided with longitudinal sipes41each extending in the tire circumferential direction from respective one of the branch portions13. The longitudinal sipes41configured as such make it easy for the branch portions13to moderately deform, therefore, it is possible that clogging of snow in the branch portions13during running on a snowy road is suppressed.

In this embodiment, the oblique grooves connected with the longitudinal sipes41and the oblique grooves not connected with the longitudinal sipes41are arranged alternately in the tire circumferential direction. Such arrangement of the longitudinal sipes41can improve the steering stability on a dry road surface and the on-snow performance in a good balance. However, it is not limited to such an embodiment, and the longitudinal sipes41may be connected to all oblique grooves.

It is preferred that each of the longitudinal sipes41has one end connected to one of the branch portions13and the other end terminating without being connected with any other grooves and sipes, for example. In a further preferred embodiment, it is preferred that the longitudinal sipes41are provided on the tire equator C (not shown inFIG. 7). The longitudinal sipes41configured as such can improve the cornering performance on ice by edges thereof while maintaining the rigidity of the land region.

It is preferred that each of the longitudinal sipes41has a length in the tire circumferential direction smaller than the groove width w2of each of the branch portions13, for example. Specifically, it is preferred that a length L6in the tire circumferential direction of each of the longitudinal sipes41is in a range of from 0.50 to 0.70 times the groove width W2of each of the branch portions13.

In this embodiment, it is preferred that sipes are not provided in the spacing portions15. Thereby, the steering stability on a dry road surface is maintained.

FIG. 8is an enlarged view of contours of the first oblique grooves10A in the embodiment shown inFIG. 7. In this embodiment, an intersection point of a groove center line of each of the first oblique grooves10A and a groove center line of one of the first joint grooves26connected with the each of the first oblique grooves10A on the toe-side in the rotational direction R is defined as a fifth intersection point42. An intersection point of the groove center line of each of the first oblique grooves10A and the groove center line of one of the first joint grooves26connected with the each of the first oblique grooves10A on the heel-side in the rotational direction R is defined as a second intersection point22. It is preferred that an angle θ7of a first straight line51extending between the fifth intersection point42and the second intersection point22with respect to the tire axial direction is in a range of from 35 to 45 degrees, for example.

In each of the first oblique grooves10A, an intersection point of a groove center line of the main body portion12and a groove center line of the branch portion13is defined as a sixth intersection point43. It is preferred that an angle θ8of a second straight line52extending between the second intersection point22and the sixth intersection point43with respect to the tire axial direction is larger than the angle θ7. More specifically, it is preferred that the angle θ8is in a range of from 45 to 55 degrees. The first oblique grooves10A configured as such can improve the on-snow traction and the cornering performance in a good balance.

It is preferred that an angle θ9with respect to the tire axial direction of a third straight line53extending between the sixth intersection point43and an end of the main body portion12of respective one of the first oblique grooves10A is larger than the angle θ8. Specifically, it is preferred that the angle θ9is in a range of from 70 to 80 degrees. In other words, a tip of each of the main body portions12is inclined at an angle in a range of from 70 to 80 degrees with respect to the tire axial direction. The main body portions12configured as such form snow blocks extending in the tire circumferential direction by the tips thereof, therefore, the cornering performance on a snowy road is improved. Further, by arranging the tips at the angle as described above, snow in the main body portions12is easily discharged from the tips during running on snow, therefore, excellent on-snow performance is continuously exerted.

As shown inFIG. 7, the shoulder blocks29in this embodiment are provided with longitudinal closed sipes45each of which extends in the tire circumferential direction and has both ends terminating within the respective block. It is preferred that the longitudinal closed sipes45are provided between the shoulder sipes34and the first tread edge Te1, for example. As a further preferred embodiment, the longitudinal closed sipes45in this embodiment extend in a zigzag manner. The longitudinal closed sipes45configured as such can moderate the behavior upon starting as well as suppress a sideslip on ice.

While detailed description has been made of the tire as an embodiment of the present invention, the present invention can be embodied in various forms without being limited to the illustrated embodiment.

Working Examples (Examples)

Tires of size 205/55R16 having the basic structure shown inFIG. 1were made by way of test according to the specification listed in Table 1. As a Reference, as shown inFIG. 6, a winter tire in which each of the branch portions is connected with its adjacent one of the oblique grooves was made by way of test. Each of the test tires was tested for the steering stability on a dry road surface and the on-snow performance. Common specifications of the test tires and the test methods are as follows.

Test car: displacement of 1800 cc

Test tire mounting position: all wheels

Groove depth of oblique grooves: 8.5 mm

Rubber hardness of tread rubber: 52

<Steering Stability on a Dry Road Surface>

While the driver was driving the test car on a dry road surface of a circuit course, the steering stability was evaluated by the driver's feeling. The results are indicated by an evaluation point based on the Reference being 100, wherein the larger the numerical value, the better the steering stability on a dry road surface is.

While the driver was driving the test car on a snowy road surface, running performance was evaluated by the driver's feeling. The results are indicated by an evaluation point based on the Reference being 100, wherein the larger the numerical value, the better the on-snow performance is.

The test results are shown in Table 1.

From the test results, it was confirmed that the tires as Examples exerted excellent steering stability on a dry road surface as compared with the winter tire as the Reference. Further, it was confirmed that the tires as the Examples had the on-snow performance as same level as that of the winter tire as the Reference.

Tires of size 205/55R16 having the basic structure shown inFIG. 7were made by way of test according to the specification listed in Table 2. As a Reference, as shown inFIG. 6, a winter tire in which each of the branch portions is connected with its adjacent one of the oblique grooves was made by way of test. Each of the test tires was tested for the steering stability on a dry road surface and the on-snow performance. Common specifications of the test tires and the test methods are the same as above.

The test results are shown in Table 2.

From the test results, it was confirmed that the tires as the Examples in the embodiment shown inFIG. 7exerted excellent steering stability on a dry road surface as compared with the winter tire as the Reference. Further, it was confirmed that the tires as the Examples mentioned above had the on-snow performance as same level as that of the winter tire as the Reference.