Patent Publication Number: US-11654721-B2

Title: Tire

Description:
TECHNICAL FIELD 
     The present invention relates to a tire, more particularly to a tire having a tread portion axially divided into four land regions. 
     BACKGROUND ART 
     Japanese Patent Application Publication No. 2015-120380 (Patent Document 1) discloses a tire having a tread portion for which a mounting direction to a vehicle is specified. In this tread portion, there are formed an outboard shoulder land region, an outboard middle land region, an inboard middle land region, and an inboard shoulder land region. And in Patent Document 1, the arrangement of grooves disposed in the outboard middle land region is specifically defined with the view to improvement in on-snow performance, while suppressing a decrease in the rigidity of the outboard middle land region. 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     In the tire of Patent Document 1, however, the outboard middle land region has a tendency that the lateral rigidity thereof becomes insufficient. This leads to deterioration in the steering stability on dry road surfaces. Therefore, the tire is required to be improved in the steering stability on dry road surfaces. 
     The present invention was made in view of the above-described problems, and it is an objective of the present invention to proved a tire of which tread portion is axially divided into four land regions and which can exhibit excellent on-snow performance and steering stability on dry road surfaces. 
     According to one aspect of the present invention, a tire whose mounting direction to a vehicle is specified, comprises: 
     a tread portion having an outboard tread edge and an inboard tread edge to be located outboard and inboard of the vehicle, respectively, when the tire is mounted on the vehicle, 
     the tread portion provided, between the inboard tread edge and the outboard tread edge, with three main grooves, 
     the three main grooves extending continuously and circumferentially of the tire so that the tread portion is axially divided into four land regions, 
     the three main grooves including 
     an outboard shoulder main groove disposed closest to the outboard tread edge among the three main grooves, and a crown main groove disposed adjacently to the outboard shoulder main groove on the inboard tread edge side of the outboard shoulder main groove, and 
     the four land regions including 
     an outboard middle land region defined between the outboard shoulder main groove and the crown main groove, wherein 
     the axial width of the outboard middle land region is the largest among the four land regions, 
     the outboard middle land region is provided with first inclined grooves each inclined to a first direction with respect to the tire axial direction, 
     second inclined grooves each inclined to the first direction with respect to the tire axial direction, and 
     fourth inclined groove inclined to a second direction with respect to the tire axial direction, the second direction being opposite to the first direction, 
     the first inclined grooves extend across the entire axial width of the outboard middle land region, 
     the second inclined grooves extend from the crown main groove and are terminated within the outboard middle land region, 
     an angle of each of the first inclined grooves with respect to the tire circumferential direction gradually increases from the crown main groove toward the outboard tread edge, 
     an angle of each of the second inclined grooves with respect to the tire circumferential direction gradually increases from the crown main groove toward the outboard tread edge, and 
     each of the fourth inclined grooves intersects one of the second inclined grooves, and intersects one of the adjacent first inclined grooves at a position on the outboard shoulder main groove side of the midpoint of the length of the first inclined groove. 
     In this application, when a groove is expressed as being connected to another groove, it is intended to mean either the two grooves intersecting with each other to form a cross junction, or the two grooves one of which meets the other without intersecting to form a T or Y junction. 
     According to another aspect of the present invention, a tire whose mounting direction to a vehicle is specified, comprises: 
     a tread portion having an outboard tread edge and an inboard tread edge to be located outboard and inboard of the vehicle, respectively, when the tire is mounted on the vehicle, 
     the tread portion provided, between the inboard tread edge and the outboard tread edge, with three main grooves, 
     the three main grooves extending continuously and circumferentially of the tire so that the tread portion is axially divided into four land regions, 
     the three main grooves including 
     an outboard shoulder main groove disposed closest to the outboard tread edge among the three main grooves, and a crown main groove disposed adjacently to the outboard shoulder main groove on the inboard tread edge side of the outboard shoulder main groove, and 
     the four land regions including an outboard middle land region defined between the outboard shoulder main groove and the crown main groove, 
     wherein 
     the axial width of the outboard middle land region is the largest among the four land regions, 
     the outboard middle land region is provided with first inclined grooves each inclined to a first direction with respect to the tire axial direction, 
     second inclined grooves each inclined to the first direction with respect to the tire axial direction, and 
     third inclined groove inclined to a second direction with respect to the tire axial direction, the second direction being opposite to the first direction, 
     the first inclined grooves extend across the entire axial width of the outboard middle land region, 
     the second inclined grooves extend from the crown main groove and are terminated within the outboard middle land region, 
     an angle of each of the first inclined grooves with respect to the tire circumferential direction gradually increases from the crown main groove toward the outboard tread edge, 
     an angle of each of the second inclined grooves with respect to the tire circumferential direction gradually increases from the crown main groove toward the outboard tread edge, and 
     at least one of the third inclined grooves intersects with one of the first inclined grooves and then intersects one of the second inclined grooves. 
     According to still another aspect of the present invention, a tire whose mounting direction to a vehicle is specified, comprises: 
     a tread portion having an outboard tread edge and an inboard tread edge to be located outboard and inboard of the vehicle, respectively, when the tire is mounted on the vehicle, 
     the tread portion provided, between the inboard tread edge and the outboard tread edge, with three main grooves, 
     the three main grooves extending continuously and circumferentially of the tire so that the tread portion is axially divided into four land regions, 
     the three main grooves including 
     an outboard shoulder main groove disposed closest to the outboard tread edge among the three main grooves, and 
     a crown main groove disposed adjacently to the outboard shoulder main groove on the inboard tread edge side of the outboard shoulder main groove, and 
     the four land regions including an outboard middle land region defined between the outboard shoulder main groove and the crown main groove, 
     wherein 
     the axial width of the outboard middle land region is the largest among the four land regions, 
     the outboard middle land region is provided with first inclined grooves each inclined to a first direction with respect to the tire axial direction, 
     second inclined grooves each inclined to the first direction with respect to the tire axial direction, and 
     fifth inclined groove inclined to a second direction with respect to the tire axial direction, the second direction being opposite to the first direction, 
     the first inclined grooves extend across the entire axial width of the outboard middle land region, 
     the second inclined grooves extend from the crown main groove and are terminated within the outboard middle land region, 
     an angle of each of the first inclined grooves with respect to the tire circumferential direction gradually increases from the crown main groove toward the outboard tread edge, 
     an angle of each of the second inclined grooves with respect to the tire circumferential direction gradually increases from the crown main groove toward the outboard tread edge, and 
     each of the fifth inclined grooves extends to one of the first inclined grooves to terminate without extending thereacross, and extends to one of the second inclined grooves to terminate without extending thereacross. 
     It is preferable that the fourth inclined grooves respectively extend across the second inclined grooves. 
     It is preferable that ends on the crown main groove side of the fourth inclined grooves are terminated within the outboard middle land region. 
     It is preferable that the fourth inclined grooves are respectively connected to the first inclined grooves on the outboard shoulder main groove side than ends on the outboard shoulder main groove side of the second inclined grooves. 
     It is preferable that the first inclined grooves each have a groove width decreasing from the outboard shoulder main groove toward the crown main groove. 
     It is preferable that the second inclined grooves each have a groove width decreasing from the crown main groove toward the outboard shoulder main groove. 
     It is preferable that each of the first inclined grooves and the second inclined grooves is curved, and the radius of curvature of the widthwise center line of the second inclined groove is smaller than the radius of curvature of the widthwise center line of the first inclined groove. 
     It is preferable that the outboard middle land region is provided with third inclined grooves inclined to the above-said second direction with respect to the tire axial direction. 
     It is preferable that each of the third inclined grooves extends from the outboard shoulder main groove to one of the second inclined grooves across one of the first inclined grooves. 
     It is preferable that each of the first inclined grooves and the third inclined grooves is curved, and the radius of curvature of the widthwise center line of the third inclined groove is larger than the radius of curvature of the widthwise center line of the first inclined groove. 
     It is preferable that the angle between the widthwise center line of the outboard shoulder main groove and the widthwise center line of each of the third inclined grooves is larger than the angle between the widthwise center line of the crown main groove and the widthwise center line of each of the first inclined grooves. 
     It is preferable that the crown main groove is disposed between the tire equator and the inboard tread edge. 
     It is preferable that the outboard middle land region is provided with fifth inclined grooves inclined to the above-said second direction with respect to the tire axial direction, and 
     each of the fifth inclined grooves extends to one of the first inclined grooves to terminate without extending thereacross, and extends to one of the second inclined grooves to terminate without extending thereacross. 
     It is preferable that the outboard middle land region is provided with: 
     third inclined grooves inclined to the second direction with respect to the tire axial direction, wherein each of the third inclined grooves extends from the outboard shoulder main groove and intersects one of the first inclined grooves and then intersects one of the second inclined grooves; and 
     fifth inclined grooves inclined to the second direction with respect to the tire axial direction, wherein each of the fifth inclined grooves extends to one of the first inclined grooves to terminate without extending thereacross, and extends to one of the second inclined grooves to terminate without extending thereacross. 
     It is preferable that the outboard middle land region is provided with: 
     third inclined grooves inclined to the second direction with respect to the tire axial direction, wherein each of the third inclined grooves extends from the outboard shoulder main groove and intersects one of the first inclined grooves and then intersects one of the second inclined grooves; 
     fifth inclined grooves inclined to the second direction with respect to the tire axial direction, wherein each of the fifth inclined grooves extends to one of the first inclined grooves to terminate without extending thereacross, and extends to one of the second inclined grooves to terminate without extending thereacross, and 
     the crown main groove is disposed between the tire equator and the inboard tread edge. 
     It is preferable that the fifth inclined grooves are respectively connected to the first inclined grooves on the crown main groove side of the axial center line of the outboard middle land region. 
     It is preferable that the fifth inclined grooves are respectively connected to the second inclined grooves on the outboard shoulder main groove side of the axial center line of the outboard middle land region. 
     It is preferable that the first inclined grooves, the second inclined grooves, and the fifth inclined grooves are each curved, and 
     the radius of curvature of the widthwise center line of each of the fifth inclined grooves is larger than the radius of curvature of the widthwise center line of each of the first inclined grooves, and larger than the radius of curvature of the widthwise center line of each of the second inclined grooves. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a developed partial view of the tread portion of a tire as an embodiment of the present invention. 
         FIG.  2    is a top view of a part of the outboard middle land region shown in  FIG.  1   . 
         FIG.  3    is a cross sectional view taken along line A-A of  FIG.  2   . 
         FIG.  4    is a cross sectional view taken along line B-B of  FIG.  2   . 
         FIG.  5    is a top view of a part of the inboard middle land region shown in  FIG.  1   . 
         FIG.  6    is a top view of a part of the outboard shoulder land region shown in  FIG.  1   . 
         FIG.  7    is a top view of a part of the tread portion of a tire as a comparative example. 
         FIG.  8    is a top view of a part of the tread portion of a tire as a reference example 1. 
         FIG.  9    is a top view of a part of the tread portion of a tire as a reference example 2. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention can be applied to various tiers such as pneumatic tires as well as non-pneumatic tires so called airless tire, for various vehicles. e.g. a passenger car and a heavy-duty vehicle such as truck and bus and the like. 
     Hereinafter, taking a pneumatic tire for a passenger car as an example, embodiments of the present invention will be described in detail conjunction with accompanying drawings. 
       FIG.  1    shows a tread portion  2  of a pneumatic tire  1  as an embodiment of the present invention. 
     As well known in the art, a pneumatic tire comprises a tread portion  2  whose radially outer surface defines the tread surface, a pair of axially spaced bead portions mounted on rim seats, a pair of sidewall portions extending between the tread edges and the bead portions, a carcass extending between the bead portions through the tread portion and the sidewall portions, and a tread reinforcement disposed radially outside the carcass in the tread portion. 
     The tread edges are the axial outermost edges of the ground contacting patch of the tire which occurs under a normally loaded condition when the camber angle of the tire is zero. 
     The tread width TW is the width measured under a unloaded condition, as the axial distance between the tread edges determined as above. 
     The unloaded condition of a pneumatic tire is such that the tire is mounted on a standard wheel rim and inflate to a standard pressure but loaded with no tire load. 
     The normally loaded condition of a pneumatic tire is such that the tire is mounted on the standard wheel rim and inflated to the standard pressure and loaded with the standard tire load. 
     The standard wheel rim is a wheel rim officially approved or recommended for the tire by standards organizations, i.e. JATMA (Japan and Asia), T&amp;RA (North America), ETRTO (Europe), TRAA (Australia), STRO (Scandinavia), ALAPA (Latin America), ITTAC (India) and the like which are effective in the area where the tire is manufactured, sold or used. 
     The standard pressure and the standard tire load are the maximum air pressure and the maximum tire load for the tire specified by the same organization in the Air-pressure/Maximum-load Table or similar list. 
     For example, the standard wheel rim is the “standard rim” specified in JATMA, the “Measuring Rim” in ETRTO, the “Design Rim” in TRA or the like. The standard pressure is the “maximum air pressure” in JATMA, the “Inflation Pressure” in ETRTO, the maximum pressure given in the “Tire Load Limits at various Cold Inflation Pressures” table in TRA or the like. The standard load is the “maximum load capacity” in JATMA, the “Load Capacity” in ETRTO, the maximum value given in the above-mentioned table in TRA or the like. 
     In this application including specification and claims, various dimensions, positions and the like of a pneumatic tire refer to those under the unloaded condition of the tire unless otherwise noted. 
     According to the present invention, the tread portion  2  of the tire is provided with a tread pattern of left-right asymmetry (asymmetry about the tire equator C). An example is shown in  FIG.  1   . 
     Thus, the mounting position of the tire with respect to a vehicle is specified. For example, the sidewall portion (not shown) of the tire to be located on outside when installed on the vehicle is provided with an indication representing “outside”, and the sidewall portion (not shown) to be located on inside is provided with an indication representing “inside”. 
     The above-said tread edges of the tread portion  2  are an outboard tread edge Te 1  to be positioned away from the center of the vehicle body and an inboard tread edge Te 2  to be positioned close to the center of the vehicle body. 
     According thereto, in this application, the terms “outboard” and “inboard” are used toward the outboard tread edge and inboard tread edge, respectively, to refer relative positions in the tire axial direction. 
     The terms “axially inner”, “axially inward” and the like are used toward the tire equator, and the terms “axially outer”, “axially outward” and the like are used toward the tread edge in order to refer relative positions in the tire axial direction. 
     In order to form the tread pattern, the tread portion  2  is provided, between the outboard tread edge Te 1  and the inboard tread edge Te 2 , with three main grooves  3  extending continuously and circumferentially of the tire. Thereby, the tread portion  2  is axially divided into four annular land regions  4 . 
     The main grooves  3  are: 
     an outboard shoulder main groove  5  disposed between the outboard tread edge Te 1  and the tire equator C and being closest to the outboard tread edge Te 1  among the three main grooves  3 ; 
     an inboard shoulder main groove  6  disposed between the inboard tread edge Te 2  and the tire equator C and being closest to the inboard tread edge Te 2  among the three main grooves  3 ; and 
     a crown main groove  7  disposed between the outboard shoulder main groove  5  and the inboard shoulder main groove  6 . 
     It is preferable that the distance La in the tire axial direction from the tire equator C to the widthwise center line of the outboard shoulder main groove  5  is set in a range from 0.20 to 0.35 times the tread width TW. 
     It is preferable that the distance La in the tire axial direction from the tire equator C to the widthwise center line of the inboard shoulder main groove  6  is set in a range from 0.20 to 0.35 times the tread width TW. 
     It is preferable that the distance Lb in the tire axial direction from the tire equator C to the widthwise center line of the crown main groove  7  is set in a range of not more than 0.15 times the tread width TW. 
     In the present embodiment, the crown main groove  7  is disposed on the inboard tread edge Te 2  side of the tire equator C. However, it may be possible to dispose the crown main groove  7  at a different location. 
     In the present embodiment, each of the three main grooves  3  is a straight groove parallel with the tire circumferential direction. However, it may be possible that the main groove  3  extends in a zigzag or wavy manner. 
     The groove width wa of each of the main grooves  3  is not less than 3.0 mm, preferably set in a range from 4.0% to 7.0% of the tread width TW, for example. 
     In the present invention, a narrow groove whose groove width is less than 3.0 mm is not considered as a main groove. Incidentally, the groove width of a groove is a distance measured between the groove edges in a direction orthogonal to the widthwise center line. 
     It is preferable that the depth of each of the main grooves  3  is set in a range from 5 to 10 mm, for example, in the case of a pneumatic tire for a passenger car. 
     The four land regions  4  are an outboard middle land region  11 , an inboard middle land region  12 , an outboard shoulder land region  13 , and a inboard shoulder land region  14 . The outboard middle land region  11  is defined between the outboard shoulder main groove  5  and the crown main groove  7 . The inboard middle land region  12  is defined between the inboard shoulder main groove  6  and the crown main groove  7 . 
     The outboard shoulder land region  13  is divided between the outboard shoulder main groove  5  and the outboard tread edge Te 1 . The inboard shoulder land region  14  is defined between the inboard shoulder main groove  6  and the inboard tread edge Te 2 . 
       FIG.  2    shows a top view of a part of the outboard middle land region  11 . 
     As shown in  FIG.  1    and  FIG.  2   , the axial width w 1  of the outboard middle land region  11  is largest among the four land regions  4 . 
     In general, when the tread portion is made up of four land regions as in the present invention, the outboard middle land region is subjected to a large ground contacting pressure during straight running and cornering. 
     In the present invention, the outboard middle land region  11  has the largest axial width to have high rigidity, therefore, the outboard middle land region  11  in the present invention helps to improve the steering stability on dry road surfaces. 
     Preferably, the axial width w 1  of the outboard middle land region  11  is set in a range from 0.25 to 0.35 times the tread width TW, for example. 
     The outboard middle land region  11  is provided with first inclined grooves  16  and second inclined grooves  17  each inclined to a first direction with respect to the tire axial direction (downward to the right in  FIG.  2   ). 
     Further, the outboard middle land region  11  is provided with third inclined grooves  18  inclined to a second direction with respect to the tire axial direction (upward to the right in  FIG.  2   ). which is opposite to the first direction, 
     Further. the outboard middle land region  11  is provided with fourth inclined grooves  19  inclined to the second direction with respect to the tire axial direction. 
     Since a large ground contacting pressure acts on the outboard middle land region  11 , each inclined groove provided on the land region  11  can provide a large compacted snow block (snow column) and thereby can generate a larger shearing force when running on snow. 
     The first inclined grooves  16  extend across the entire axial width of the outboard middle land region  11 . Therefore, the first inclined groove  16  can produce an axially long snow block when running on snow, and thereby traction performance on snow can be improved. 
     The second inclined grooves  17  extend from the crown main groove  7  toward the outboard shoulder main groove  5 , but terminate within the outboard middle land region  11 , without reaching the outboard shoulder main groove  5 . 
     such second inclined grooves  17  can improve the performance on snow, while maintaining the rigidity of the outboard middle land region  11  and maintaining the steering stability on dry road surfaces. 
     The angle of the widthwise center line of each of the first inclined grooves  16  with respect to the tire circumferential direction, and 
     the angle of the widthwise center line of each of the second inclined grooves  17  with respect to the tire circumferential direction 
     are gradually increased from the crown main groove  7  to the outboard tread edge Te 1 . As a result, the lateral rigidity of the outboard middle land region  11  is increased toward the outboard shoulder main groove  5 , and the steering stability on dry road surfaces is improved. 
     Each of the fourth inclined grooves  19  is connected to one of the second inclined grooves  17 . 
     Further, each of the fourth inclined grooves  19  is connected to one of the first inclined grooves  16  at a position on the outboard shoulder main groove  5  side of the midpoint of the length of the first inclined groove  16 . During cornering, such fourth inclined grooves  19  form hard compacted snow blocks, particularly at the portions communicating with the first inclined grooves  16 . This helps to improve the cornering performance on snowy road surfaces. 
     The first inclined grooves  16  are each curved so that the widthwise center line curves to protrude toward one side in the tire circumferential direction (upward in  FIG.  2   ) from a straight line drawn between both ends of the widthwise center line. 
     The radius of curvature of the widthwise center line of the first inclined groove  16  is, for example, set in a range from 50 to 200 mm, and more preferably, 90 to 110 mm. 
     If the widthwise center line of the inclined groove is not an accurate circular arc, the radius of curvature means that of an imaginary circular arc passing through three points at both ends of the widthwise center line and a midpoint of the length of the widthwise center line. 
     The angle of the widthwise center line of the inclined groove  16  with respect to the tire circumferential direction is preferably, set in a range from 45 to 55 degrees, for example. Such first inclined grooves  16  can generate a snow block shearing force in multiple directions. 
     The first inclined grooves  16  each have a groove width decreasing from the outboard shoulder main groove  5  toward the crown main groove  7 , and the groove width at its end on the outboard shoulder main groove  5  side is larger than the groove width at its end on the crown main groove  7  side. 
     The groove width at the end on the outboard shoulder main groove  5  side is set in a range from 6.0 to 8.0 mm, for example. The groove width at the end on the crown main groove  7  side is set in a range from 5.0 to 7.0 mm, for example. 
       FIG.  3    is a cross-sectional view of the first inclined groove  16  taken along line A-A of  FIG.  2    (widthwise center line). As shown in  FIG.  3   , the first inclined groove  16  comprises an outer part  16   a  connected to the outboard shoulder main groove  5 , and 
     an inner part  16   b  connected to the crown main groove  7 . The inner part  16   b  has a smaller depth than the outer part  16   a . For example, the depth d 2  of the inner part  16   b  is set in a range from 0.40 to 0.70 times the depth d 1  of the outer part  16   a . The inner part  16   b  is formed on the crown main groove  7  side than the center in the tire axial direction of the outboard middle land region  11 .
 
Such inner parts  16   b  help to improve the steering stability on dry road surfaces.
 
     It is preferable that, as shown in  FIG.  2   , the second inclined grooves  17  extend across the axial or widthwise center line  11   c  of the outboard middle land region  11 . 
     Preferably, the axial length L 1  of the second inclined groove  17  is set in a range from 0.70 to 0.85 times the axial width w 1  of the outboard middle land region  11 , for example. 
     Such second inclined grooves  17  help to improve the on-snow performance and the steering stability on dry road surfaces in a well-balanced manner. 
     The second inclined grooves  17  are curved in the same direction as the first inclined grooves  16 . 
     Preferably, the radius of curvature of the widthwise center line of each of the second inclined grooves  17  is smaller than the radius of curvature of the widthwise center line of each of the first inclined grooves  16 . 
     The difference in radius of curvature between the second inclined grooves  17  and the first inclined grooves  16  is in a range from 10 to 50 mm, for example. 
     The radius of curvature of the second inclined grooves  17  is set in a range from 50 to 200 mm, and more preferably, 80 to 110 mm. 
     Preferably, the angle of the widthwise center line of each of the second inclined grooves  17  with respect to the tire circumferential direction is set in a range from 45 to 55 degrees, for example. 
     It is it is preferable that the second inclined grooves  17  each have a groove width decreasing from the crown main groove  7  toward the outboard shoulder main groove  5 , and the groove width at its end on the crown main groove  7  side is larger than the groove width at its terminal end positioned within the outboard middle land region  11 . 
     The groove width at the end on the crown main groove  7  side is set in a range from 10.0 to 12.0 mm, for example. 
     The groove width at the terminal end is set in a range from 1.0 to 3.0 mm, for example. Here, the groove width at the terminal end is measured at a position excluding the arc-shaped edge at the terminal end. 
     The second inclined grooves  17  together with the first inclined grooves  16  provide a large snow block shearing force, while maintaining the rigidity of the outboard middle land region  11 . 
     More preferably, the groove width of each of the second inclined grooves  17  in the present embodiment is gradually decreased from the crown main groove  7  to its terminal end positioned within the outboard middle land region  11 . 
     Such second inclined grooves  17  can further suppress the decrease in the rigidity of the outboard middle land region  11 . 
     Preferably, the opening width w 5  of the second inclined groove  17  to the crown main groove  7  is larger than the opening width W 4  of the first inclined groove  16  to the outboard shoulder main groove  5 . For example, the opening width W 5  is in a range from 1.2 to 1.5 times the opening width W 4 . 
     This makes it easier for water existing in the second inclined grooves  17  to be discharged toward the outboard shoulder main groove  5  through the first inclined grooves  16  during running in wet conditions. 
       FIG.  4    is a cross sectional view of the second inclined groove  17  taken along line B-B of  FIG.  2    (widthwise center line). 
     Preferably, the depth of each of the second inclined grooves  17  is gradually decreased from the crown main groove  7  toward the outboard shoulder main groove  5  as shown in  FIG.  4   . Such second inclined grooves  17  together with the first inclined grooves  16  improve the performance on snow and the steering stability on dry road surfaces in a well-balanced manner. 
     The second inclined groove  17  comprises a first constant depth portion  17   a , a second constant depth portion  17   b , and a variable depth portion  17   c  therebetween. 
     The first constant depth portion  17   a  has a constant depth along its length and is connected to the crown main groove  7 . 
     Preferably, the first constant depth portion  17   a  has the same depth as the outer part  16   a  of the first inclined groove  16  shown in  FIG.  3   . 
     The second constant depth portion  17   b  is disposed on the outboard shoulder main groove  5  side of the first constant depth portion  17   a.    
     The second constant depth portion  17   b  has a constant depth d 4  along its length, and the constant depth d 4  is a smaller depth than that of the first constant depth portion  17   a.    
     Preferably, the second constant depth portion  17   b  has the same depth as the inner part  16   b  of the first inclined groove  16 . The depth d 4  of the second constant depth portion  17   b  is, for example, set in a range from 0.40 to 0.70 times the depth d 3  of the first constant depth portion  17   a.    
     The variable depth portion  17   c  has a bottom surface inclined with respect to the tire axial direction, and the depth gradually decreases from the first constant depth portion  17   a  to the second constant depth portion  17   b.    
     At least one of the third inclined grooves  18  is connected to one of the first inclined grooves  16  and one of the second inclined grooves  17 . 
     Preferably, each of the third inclined grooves  18  extends from the outboard shoulder main groove  5  and intersects one of the first inclined grooves  16  and then meets intersects one of the second inclined grooves  17  without intersecting as shown in  FIG.  2   . 
     The third inclined grooves  18  respectively intersect the first inclined grooves  16  and meet the second inclined grooves  17  on the crown main groove  7  side of the axial or widthwise center line  11   c  of the outboard middle land region  11 . 
     The third inclined groove  18  intersects a variable depth portion (shown in  FIG.  3   ) of the first inclined groove  16 . 
     Further, the third inclined groove  18  is connected to the first constant depth portion  17   a  (shown in  FIG.  4   ) of the second inclined groove  17 . 
     When running on snow, such third inclined grooves  18  can strongly compact the snow in the intersecting portions with the first inclined grooves  16  and the second inclined grooves  17  and can further improve the performance on snow. 
     The third inclined grooves  18  extend from the outboard shoulder main groove  5  toward the crown main groove  7 , and preferably extend across the axial center line  11   c . The third inclined grooves  18  respectively cross the first inclined grooves  16  on the crown main groove  7  side of the axial center line  11   c.    
     Preferably, the angle θ 1  between the widthwise center line of the first inclined groove  16  and the widthwise center line of the third inclined groove  18  is set in a range from 40 to 55 degrees, for example. 
     Each of the third inclined grooves  18  is connected to one of the second inclined grooves  17  near the end on the crown main groove side  7  of the second inclined groove  17 , and terminates without crossing the second inclined groove  17 . 
     The third inclined groove  18  is curved so that the groove widthwise center line protrudes from a straight line drawn between both ends of the widthwise center line toward the other side in the tire circumferential direction than that of the first inclined grooves  16  (downward in  FIG.  2   ). 
     Preferably, the radius of curvature of the widthwise center line of the third inclined groove  18  is larger than the radius of curvature of the widthwise center line of the first inclined groove  16 . 
     The difference in radius of curvature between the third inclined grooves  18  and the first inclined grooves  16  is, for example, 50 to 200 mm. 
     Preferably, the radius of curvature of the widthwise center line of the third inclined groove  18  is 150 to 450 mm, for example. 
     It is preferable that the angle of the widthwise center line of the third inclined groove  18  with respect to the tire circumferential direction gradually decreases toward the crown main groove  7 . Preferably, the angle is set in a range from 60 to 80 degrees, for example. 
     It is preferable that the angle between the widthwise center lines of the outboard shoulder main groove  5  and the third inclined groove  18  is larger than the angle between the widthwise center lined of the crown main groove  7  and the first inclined groove  16 . 
     Thereby, the rigidity of the outboard middle land region  11  near the outboard shoulder main groove  5  becomes relatively high, and thus the behavior of the vehicle when a large steering angle is given to the tires on dry road surfaces is stabilized. 
     It is preferable that the groove width of the third inclined groove  18  is constant along its length. The groove width is set in a range from 2.0 to 3.0 mm, for example. 
     It is preferable that the depth of the third inclined groove  18  is constant along its length. 
     In the present embodiment, the depth of the third inclined grooves  18  is smaller than the depth of the outer part  16   a  of the first inclined grooves  16  and 
     the depth of the first constant depth portion  17   a  of the second inclined grooves  17 . 
     Preferably, the depth of the third inclined grooves  18  is the same as the depth of the inner part  16   b  of the first inclined groove  16  and the depth of the second constant depth portion  17   b  of the second inclined groove  17 . 
     Further, the bottom surface of the third inclined groove  18  may be provided with a sipe (not shown) extending along the length of the third inclined groove  18 . 
     Here, the term “sipe” means a narrow groove having a width not more than 1.5 mm inclusive of a cut having no substantial width. 
     The third inclined grooves  18  provided with the sipes can improve the steering stability on dry road surfaces while maintaining the performance on snow. 
     Preferably, the above-mentioned fourth inclined grooves  19  are respectively connected to the first inclined grooves  16  at an axial position on the outboard shoulder main groove  5  side than the ends on the outboard shoulder main groove  5  side of the second inclined grooves  17 . 
     In the present embodiment, the fourth inclined groove  19  is connected to the outer part  16   a  (shown in  FIG.  3   ) of the first inclined groove  16 . 
     Given the axial distance L 2  (shown in  FIG.  2   ) from a position at which the widthwise center line of the fourth inclined groove  19  intersects the first inclined groove  16  (groove edge) to the outboard shoulder main groove  5  (groove edge), the axial distance L 2  is preferably set in a range from 0.05 to 0.20 times the axial width w 1  of the outboard middle land region  11 . 
     As a result, the on-snow performance and the steering stability on dry road surfaces are improved in a well-balanced manner. 
     The fourth inclined grooves  19  extend across the axial center line  11   c . And the fourth inclined grooves  19  respectively intersect with the second inclined grooves  17  on the crown main groove  7  side of the axial center line  11   c . In the present embodiment, the fourth inclined groove  19  intersects the first constant depth portion  17   a  (shown in  FIG.  4   ) of the second inclined groove  17 . 
     The ends on the crown main groove side  7  of the fourth inclined grooves  19  terminate within the outboard middle land region  11 . Therefore, the fourth inclined grooves  19  intersect the deeper portions of the first inclined grooves  16  and the second inclined grooves  17 , and can form hard snow blocks (columns) at the intersections of the grooves.
 
The axial length of the fourth inclined groove  19  is smaller than the axial length of the third inclined groove  18 .
 
Such fourth inclined grooves  19  can improve the performance on snow, while maintaining the rigidity of the outboard middle land region  11 .
 
     For example, the fourth inclined grooves  19  are preferably convexly curved in the same direction as the third inclined grooves  18 . Preferably, the radius of curvature of the widthwise center line of the fourth inclined groove  19  is set in a range from 150 to 450 mm, for example. In the present embodiment, the radius of curvature of the fourth inclined grooves  19  is the same as that of the third inclined grooves  18 . Such fourth inclined grooves  19  can further maintain the rigidity of the outboard middle land region  11 . 
     It is preferable that the angle between the fourth inclined groove  19  and the outboard shoulder main groove  5  is larger than the angle between the first inclined groove  16  and the crown main groove  7 , and larger than the angle between the second inclined groove  17  and the crown main groove  7 . 
     Preferably, the angle between the fourth inclined groove  19  and the outboard shoulder main groove  5  is set in a range from 60 to 80 degrees, for example. 
     Preferably, the angle θ 2  between the first inclined groove  16  and the fourth inclined groove  19  is set in a range from 45 to 55 degrees, for example. 
     Here, each angle is between the grooves&#39; widthwise center lines. 
     It is preferable that the groove width of the fourth inclined groove  19  is constant along its length. 
     It is preferable that the groove width of the fourth inclined grooves  19  is larger than the groove width of the third inclined grooves  18 , and smaller than the maximum groove width of the first inclined grooves  16 . It is preferable that the maximum depth of the fourth inclined grooves  19  is larger than the maximum depth of the third inclined grooves  18 .
 
Such fourth inclined grooves  19  can improve the on-snow performance and the steering stability on dry road surfaces in a well-balanced manner.
 
     In the fourth inclined groove  19  in the present embodiment, its tip portion  19   a  on the crown main groove  7  side of the intersecting second inclined groove  17  is smaller in the groove depth than its main portion  19   b  on the outboard shoulder main groove  5  side of the second inclined groove  17 . 
     Such fourth inclined grooves  19  help to improve the steering stability on dry road surfaces. 
     The outboard middle land region  11  in the present embodiment is provided with fifth inclined grooves  20 . 
     The fifth inclined grooves  20  meet the respective first inclined grooves  16  without intersecting, so as to form T-junctions. Further, the fifth inclined grooves  20  meet the respective second inclined grooves  17  without intersecting, so as to form T-junctions. 
     However, the present invention is not limited to such T-junctions, and the fifth inclined grooves  20  may intersect the first inclined grooves  16  and/or the second inclined grooves  17  to form cross junctions. 
     The fifth inclined grooves  20  meet the first inclined grooves  16  on the crown main groove  7  side of the axial center line  11   c . The fifth inclined grooves  20  meet the second inclined grooves  17  on the outboard shoulder main groove  5  side of the axial center line  11   c . Thus, the fifth inclined grooves  20  extend across the axial center line  11   c.    
     specifically, the fifth inclined groove  20  meets the inner part  16   b  (shown in  FIG.  3   ) of the first inclined groove  16 , and meets the second constant depth portion  17   b  (shown in  FIG.  4   ) of the second inclined groove  17 . 
     By being connected to the portions of the first inclined grooves  16  and the second inclined grooves  17  where the groove depths are small, the fifth inclined grooves  20  can maintain the rigidity of the land region. 
     It is preferable that the axial length of each of the fifth inclined grooves  20  is smaller than that of the fourth inclined grooves  19 . 
     The fifth inclined grooves  20  are inclined to the above-said second direction with respect to the tire axial direction. The fifth inclined grooves  20  extend parallel with the fourth inclined grooves  19 . 
     The angle θ 3  between the widthwise center lines of the second inclined groove  17  and the fifth inclined groove  20  is preferably set in a range from 45 to 55 degrees. 
     In the present embodiment, the fifth inclined grooves  20  are curved in the same direction as the third inclined grooves  18 . 
     Preferably, the radius of curvature of the widthwise center line of the fifth inclined groove  20  is larger than the radius of curvature of the widthwise center line of the first inclined groove  16  and the radius of curvature of the widthwise center line of the second inclined groove  17 .
 
Specifically, the radius of curvature of the fifth inclined groove  20  is set in a range from 180 to 440 mm.
 
     It is preferable that the groove width of the fifth inclined grooves  20  is constant along its length. 
     It is preferable that the groove width of the fifth inclined grooves  20  is larger than the groove width of the fourth inclined grooves  19  and smaller than the maximum groove width of the first inclined grooves  16 . 
     Further, it is preferable that the maximum depth of the fifth inclined grooves  20  is smaller than the maximum depth of the fourth inclined grooves  19 . 
     The outboard middle land region  11  in the present embodiment is preferably provided with sipes  25  in order to improve on-snow performance and wet performance. 
     Preferably, the width of the sipes  25  is set in a range from 0.4 to 1.0 mm, for example. 
     Preferably, the sipes  25  are inclined to the second direction with respect to the tire axial direction. 
     Further, the sipes  25  are preferably convexly curved in the same direction as the third inclined grooves  18 . 
     Such sipes  25  provide large frictional force by their edges while maintaining the rigidity of the outboard middle land region  11 . 
     The sipes  25  in the present embodiment are: 
     plural pairs of a first sipe  26  and a second sipe  27  each extending from the outboard shoulder main groove  5  to one of the second inclined grooves  17 , 
     third sipes  28  extending from the crown main groove  7  to the respective first inclined grooves  16 , and 
     fourth sipes  29  respectively extending from the fourth inclined grooves  19  to the first inclined grooves  16  as shown in  FIG.  2   . 
     Each of the first sipes  26  extends from the outboard shoulder main groove  5 , and intersects one of the first inclined grooves  16 , and extends through between the adjacent third inclined groove  18  and fourth inclined groove  19 , and then meets one of the second inclined grooves  17  without intersecting, on the crown main groove  7  side of the axial center line  11   c . Preferably, the first sipes  26  extend parallel with the third inclined grooves  18 . 
     Each of the second sipes  27  extends from the outboard shoulder main groove  5  through between the adjacent third inclined groove  18  and fourth inclined groove  19 , and meets one of the second inclined grooves  17  without intersecting, on the outboard shoulder main groove  5  side of the axial center line  11   c . As to the meeting position of the second sipe  27  with the second inclined groove  17 , it is preferable that the second sipe  27  meets an extension of the fifth inclined groove  20  toward the outboard shoulder main groove  5 . 
     Preferably, the second sipes  27  extend parallel with the fourth inclined grooves  19 . 
     Each of the third sipes  28  is disposed between the adjacent first inclined groove  16  and second inclined groove  17 , on the crown main groove  7  side of the axial center line  11   c . Each of the third sipes  28  extends from the crown main groove  7  toward the outboard shoulder main groove  5  and meets one of the first inclined grooves  16  without intersecting. 
     As to the meeting position of the third sipe  28  with the first inclined groove  16 , it is preferable that the third sipe  28  meets an extension of the fifth inclined groove  20  toward the crown main groove  7 . 
     Preferably, the third sipes  28  extend parallel with the third inclined grooves  18 . 
     Each of the fourth sipes  29  is disposed on the crown main groove  7  side of the axial center line  11   c  and extends from one of the first inclined grooves  16  to the end of one the fourth inclined grooves  19 . 
     Preferably, the fourth sipes  29  extend parallel with the fifth inclined grooves  20 . 
       FIG.  5    shows a part of the inboard middle land region  12 . The axial width w 2  of the inboard middle land region  12  is preferably set in a range from 0.10 to 0.20 times the tread width TW, for example. 
     The inboard middle land region  12  in this example is provided with middle lateral grooves  30  extending from the crown main groove  7  and terminated within the inboard middle land region  12 . 
     As shown in  FIG.  5   , the middle lateral groove  30  comprises 
     a first portion  31  extending from the crown main groove  7  while inclining to the first direction with respect to the tire axial direction, and 
     a second portion  32  extending continuously from the first portion  31  in the tire circumferential direction. Preferably, the depth of the second portion  32  is smaller than the depth of the first portion  31 . 
     when running on snow, the middle lateral groove  30  can generate snow block (column) shearing force in the tire circumferential direction and tire axial direction, while maintaining steering stability on dry road surfaces. 
     The inboard middle land region  12  is further provided with first middle sipes  33  and second middle sipes  34 . 
     The first middle sipes  33  extend from the crown main groove  7  and terminate within the inboard middle land region  12 . 
     The second middle sipes  34  extend from the inboard shoulder main groove  6 , and meet the respective middle lateral grooves  30 . 
     The inboard middle land region  12  in the present embodiment is further provided with a sipe combination  35  made up of two sipes  36  and multiple cuts extending between the two sipes  36 . 
     The two sipes  36  in this example extend from one of the first middle sipes  33  to the first portion  31  of one of the middle lateral grooves  30 , while gradually decreasing the distance therebetween. 
     In this example, the sipe combination  35  is provided for every other first middle sipe  33  as shown in  FIG.  5   . 
     Such sipe combination  35  helps to improve grip performance at the start of use of the tire. 
       FIG.  6    shows a part of the outboard shoulder land region  13 . 
     Preferably, the axial width w 3  of the outboard shoulder land region  13  is larger than the axial width w 2  of the inboard middle land region  12  as shown in  FIG.  1   . 
     Preferably, the axial width w 3  is set in a range from 0.15 to 0.25 times the tread width TW, for example. 
     The outboard shoulder land region  13  is provided with shoulder lateral grooves  40  extending in the tire axial direction, and 
     shoulder sipes  41  extending in the tire axial direction. such shoulder lateral grooves  40  and shoulder sipes  41  help to improve the performance on snow. 
     Similarly to the outboard shoulder land region  13 , the inboard shoulder land region  14  is also provided with shoulder lateral grooves  40  extending in the tire axial direction, and 
     shoulder sipes  41  extending in the tire axial direction as shown in  FIG.  1   . 
     Preferably, the inboard shoulder land region  14  is provided with a chamfer  42  extending between the ground contacting top surface of the inboard shoulder land region  14  (constituting a part of the tread surface) and the side surface on the inboard shoulder main groove  6  side of the inboard shoulder land region  14 . 
     Preferably, the chamfer  42  is provided with narrow grooves (not shown) extending from the tread surface to the above-said side surface. Thereby, grip performance on snow can be further improved. 
     While detailed description has been made of a preferable embodiment of the present invention, the present invention can be embodied in various forms without being limited to the illustrated embodiment. 
     Comparison Test 1 
     Pneumatic tires of size 215/60R16 were experimentally manufactured as test tires including: 
     embodiment tires (Ex.1-Ex.9) having tread patterns based on the tread pattern shown in  FIG.  1   ; and 
     a comparative example tire (Com) having a tread pattern substantially the same as that shown in  FIG.  1    except that, as shown in  FIG.  7   , the outboard middle land region (a) was provided with a fourth inclined groove (d) intersecting with the second inclined groove (c) and not intersecting with the first inclined groove (b). 
     Each test tire was tested for on-snow performance and steering stability on dry road surfaces as follows, using a 2500 cc front wheel drive passenger car as a test car where the test tires were mounted on standard wheel rims of size 16×6.5 and inflated to 240 kPa. 
     &lt;On-Snow Performance&gt; 
     Snow Performance of Each Test Tire when the Test Car was Running on a snowy road was evaluated by the test driver. 
     The results are shown in Table 1 by an index based on the comparative example being 100, wherein the larger the numerical value, the better the on-snow performance. 
     &lt;Steering Stability on Dry Road Surfaces&gt; 
     steering stability when the test car was running on a dry road surface was evaluated by the test driver. 
     The results are shown in Table 1 by an index based on the comparative example being 100, wherein the larger the numerical value, the better the steering stability on dry road surfaces. 
     
       
         
           
               
               
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Tire 
                 Com 
                 Ex. 1 
                 Ex. 2 
                 Ex. 3 
                 Ex. 4 
                 Ex. 5 
                 Ex. 6 
                 Ex. 7 
                 Ex. 8 
                 Ex. 9 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 outboard middle land 
                 7 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
               
               
                 region (FIG. No.) 
               
               
                 W1/TW 
                 0.30 
                 0.30 
                 0.25 
                 0.28 
                 0.32 
                 0.35 
                 0.30 
                 0.30 
                 0.30 
                 0.30 
               
               
                 L2/W1 
                 — 
                 0.12 
                 0.12 
                 0.12 
                 0.12 
                 0.12 
                 0.05 
                 0.10 
                 0.15 
                 0.20 
               
               
                 on-snow performance 
                 100 
                 107 
                 107 
                 107 
                 106 
                 105 
                 108 
                 107 
                 107 
                 105 
               
               
                 steering stability 
                 100 
                 102 
                 101 
                 102 
                 103 
                 103 
                 100 
                 101 
                 102 
                 102 
               
               
                   
               
            
           
         
       
     
     From the test results, it was confirmed that the embodiment tires exhibited excellent on-snow performance and steering stability on dry road surfaces. 
     Comparative Test 2 
     Pneumatic tires of size 215/60R16 were experimentally manufactured as test tires including: 
     embodiment tires (Ex.10-Ex.18) having tread patterns based on the tread pattern shown in  FIG.  1   , and 
     a reference example tire (Ref.1) having a tread pattern which was the substantially same as that shown in  FIG.  1    except that, as shown in  FIG.  8   , 
     the outboard middle land region (e) was provided with inclined grooves (f) extending across the entire axial width of the land region (e), and inclined grooves (g) intersecting only with the respective inclined groove (f), and provided with no grooves corresponding to the second inclined grooves  17  and third inclined grooves  18 . 
     Each test tire was tested for on-snow performance and steering stability on dry road surfaces in the same manner as described above. 
     The test results are shown in Table 2 by an index based on the reference example tire Ref.1 being 100, wherein the larger the numerical value, the better the performance. 
     
       
         
           
               
               
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 Tire 
                 Ref. 1 
                 Ex. 10 
                 Ex. 11 
                 Ex. 12 
                 Ex. 13 
                 Ex. 14 
                 Ex. 15 
                 Ex. 16 
                 Ex. 17 
                 Ex. 18 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 outboard middle land 
                 8 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
               
               
                 region (FIG. No.) 
               
               
                 W1/TW 
                 0.30 
                 0.30 
                 0.25 
                 0.28 
                 0.32 
                 0.35 
                 0.30 
                 0.30 
                 0.30 
                 0.30 
               
               
                 L1/W1 
                 — 
                 0.78 
                 0.78 
                 0.78 
                 0.78 
                 0.78 
                 0.70 
                 0.75 
                 0.80 
                 0.85 
               
               
                 on-show performance 
                 100 
                 106 
                 106 
                 106 
                 105 
                 104 
                 105 
                 106 
                 106 
                 107 
               
               
                 steering stability 
                 100 
                 103 
                 101 
                 102 
                 103 
                 102 
                 103 
                 103 
                 102 
                 101 
               
               
                   
               
            
           
         
       
     
     From the test results, it was confirmed that the embodiment tires exhibited excellent on-snow performance and steering stability on dry road surfaces. 
     Comparative Test 3 
     Pneumatic tires of size 215/60R16 were experimentally manufactured as test tires including: 
     embodiment tires (Ex.19-Ex.27) having tread patterns based on the tread pattern shown in  FIG.  1   , and 
     a reference example tire (Ref.2) having a tread pattern which was the substantially same as that shown in  FIG.  1    except that, as shown in  FIG.  9   , the outboard middle land region (h) was provided with fifth inclined grooves (k) intersecting with respective second inclined grooves (j) and not connected to first inclined grooves (i). 
     Each test tire was tested for steering stability on dry road surfaces in the same manner as described above. 
     The test results are shown in Table 3 by an index based on the reference example tire Ref.2 being 100, wherein the larger the numerical value, the better the performance. 
     Further, each test tire was tested for wet performance as follows. 
     &lt;Wet Performance&gt; 
     wet performance of each test tire when the test car was running on a wet road surface was evaluated by the test driver. 
     The results are shown in Table 3 by an index based on the reference example tire Ref.2 being 100, wherein the larger the numerical value, the better the wet performance. 
     
       
         
           
               
               
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                 Tire 
                 Ref.2 
                 Ex. 19 
                 Ex. 20 
                 Ex. 21 
                 Ex. 22 
                 Ex. 23 
                 Ex. 24 
                 Ex. 25 
                 Ex. 26 
                 Ex. 27 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 outboard middle land 
                 9 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
               
               
                 region (FIG. No.) 
               
               
                 W1/TW 
                 0.30 
                 0.30 
                 0.25 
                 0.28 
                 0.32 
                 0.35 
                 0.30 
                 0.30 
                 0.30 
                 0.30 
               
               
                 angle θ3 (deg.) 
                 50 
                 50 
                 50 
                 50 
                 50 
                 50 
                 40 
                 45 
                 55 
                 60 
               
               
                 steering stability 
                 100 
                 102 
                 101 
                 102 
                 103 
                 103 
                 101 
                 102 
                 102 
                 101 
               
               
                 wet performance 
                 100 
                 105 
                 104 
                 105 
                 104 
                 103 
                 103 
                 104 
                 105 
                 105 
               
               
                   
               
            
           
         
       
     
     From the test results, it was confirmed that the embodiment tires exhibited excellent wet performance while maintaining steering stability on dry road surfaces. 
     DESCRIPTION OF THE REFERENCE SIGNS 
     
         
         
           
               2  tread portion 
               3  main groove 
               4  land portion 
               5  outboard shoulder main groove 
               7  crown main groove 
               11  outboard middle land region 
               16  first inclined groove 
               17  second inclined groove 
               19  fourth inclined groove 
             Te 1  outboard tread edge 
             Te 2  inboard tread edge