JP6564311B2 - Pneumatic tires for motorcycles - Google Patents

Description

  The present invention relates to a pneumatic tire for a motorcycle (hereinafter, also simply referred to as “tire”). Specifically, until the performance of a new tire can be exhibited at an early stage and the new tire can sufficiently exhibit performance. The present invention relates to a pneumatic tire for a motorcycle capable of visually confirming wear.

  In the vulcanization process in the manufacturing process of a pneumatic tire, generally, a tire vulcanization bladder is arranged inside an unvulcanized tire arranged in a mold, and the tire vulcanization bladder is expanded by steam. This is performed by bringing an unvulcanized tire into close contact with the mold. The vulcanized tire is taken out from the vulcanizer, and at this time, the vulcanized tire needs to be smoothly peeled off from the vulcanizer.

  In order to deal with such problems, conventionally, the adhesion of the vulcanized tire has been prevented by spraying a mold release agent such as silicone in advance on the upper mold part of the vulcanizer. In addition to this, for example, in Patent Document 1, a modification is provided in which a peeling jig is provided without using a mold release agent, and a contrivance is made such as peeling off the adhered vulcanized tire.

JP-A-6-218734

  Tires manufactured using a release agent during vulcanization of unvulcanized tires will exhibit the original performance of the tire when it is new because the silicone, which is a component of the release agent, is transferred to the tread. I can't do it. Therefore, in order to fully demonstrate the performance of a new tire, it is necessary to wear a certain amount of the tread portion and remove the silicone and the like that have moved to the tread portion.

  Accordingly, an object of the present invention is to provide a pneumatic tire for a motorcycle that can exhibit the performance of a new tire at an early stage and can visually confirm that the new tire has been worn until it can fully perform. Is to provide.

  As a result of intensive studies to solve the above problems, the present inventors have obtained the following knowledge. In other words, by providing a shallow groove in the tread portion, the wear of the tread portion at the time of a new article is promoted, the performance of the new tire can be exhibited at an early stage, and the new tire is worn until the performance can be sufficiently exhibited. This can be confirmed visually, and it has been found that the above-mentioned problems can be solved, and the present invention has been completed.

That is, the pneumatic tire for motorcycles of the present invention is a pneumatic tire for motorcycles having a tread portion formed in an annular shape,
A shallow groove having a width of 0.1 to 2.0 mm and a depth of 0.1 to 2.0 mm is provided in the tread portion in the tire width direction, and the length of the shallow groove is the width of the tire contact surface. It is characterized by being arranged at intervals shorter than the length of the tire ground contact surface. Here, the tire width direction used when indicating the extending direction of the shallow groove includes a range of more than −45 ° and less than 45 ° with respect to a direction perpendicular to the tire equator. When the shape of the shallow groove is not a straight line, the direction of the shallow groove is the direction of a line connecting both ends of the shallow groove.

  In the tire of the present invention, the number of shallow grooves may be greater in the center region than in the shoulder region of the tread portion, and may be greater in the shoulder region than in the center region of the tread portion. In the tire of the present invention, the depth of the shallow groove may be deeper in the center region than the shoulder region of the tread portion, and deeper in the shoulder region than the center region of the tread portion. Also good. Further, in the tire according to the present invention, the width of the shallow groove may be wider in the center region than the shoulder region of the tread portion, and the width of the shallow groove is larger than the shoulder region of the center region of the tread portion. The area may be larger.

  Here, the center region of the tread portion is a straight contact region when the tire is mounted on a specified rim, filled with a specified internal pressure, and a maximum load is applied, and the shoulder region is a region in the tread portion. An area outside the center area in the tire width direction. In addition, the “specified rim” here refers to a standard rim (or “Applied Rim” or “Recommended Rim”) at an applicable size described in a predetermined industrial standard. Air pressure corresponding to the maximum load (maximum load capacity) of a single wheel in the described application size. Further, the maximum load load is the maximum load (maximum load capacity) of a single wheel at the applicable size described in the same standard. For such industrial standards, valid standards are established for each region where tires are produced or used. For example, in the United States, “The Tire and Rim Association Inc. Year Book” (including design guides) ) In Europe by “The European Tire and Rim Technical Organizations Manual”, and in Japan by “JATMA YEAR BOOK” of the Japan Automobile Tire Association. Furthermore, in the tire of the present invention, the width of the contact surface refers to the length of the widest portion in the width direction on the contact surface at normal load and normal internal pressure.

  According to the present invention, there is provided a pneumatic tire for a motorcycle that can exhibit the performance of a new tire at an early stage and that can be visually confirmed that the new tire has been worn until it can fully perform. can do.

1 is a schematic development view of a tread portion of a pneumatic tire for a motorcycle according to a preferred embodiment of the present invention. 1 is a schematic plan view showing an example of the shape of a shallow groove of a pneumatic tire for a motorcycle according to a preferred embodiment of the present invention. FIG. 3 is a schematic sectional view showing an example of a change in depth in the extending direction of the shallow groove according to the pneumatic tire for a motorcycle of the present invention. It is a schematic plan view showing an example of a change in the width of the shallow groove according to the pneumatic tire for motorcycles of the present invention. It is a schematic sectional view showing an example of a cross-sectional shape in the groove width direction of the shallow groove according to the pneumatic tire for motorcycles of the present invention. 1 is a schematic cross-sectional view in the width direction of a pneumatic tire for a motorcycle according to a preferred embodiment of the present invention.

  Hereinafter, the pneumatic tire for motorcycles of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic development view of a tread portion of a pneumatic tire for a motorcycle according to a preferred embodiment of the present invention. In addition, the arrow in a figure is a rotation direction, and a tire will be earth | grounded from the arrow side during driving | running | working. The tire of the present invention includes a tread portion 1 formed in an annular shape, and a shallow groove 2 is provided in the tread portion 1 in the tire width direction (hereinafter also referred to as “width direction shallow groove 2”). In the example shown in the figure, one row is provided for the center region Tc and one row for each shoulder region Ts. In the illustrated example, the two main grooves 3a and 3b are periodically provided at an equal pitch. However, the shape of the main groove 3 is not particularly limited and is not limited to the above example. . For example, a circumferential groove formed continuously in the circumferential direction may be provided as the main groove.

  In the tire of the present invention, the following effects can be obtained by providing the shallow groove 2 in the tread portion 1. First, in a new tire, since the silicone used in the tire vulcanization process is present on the surface layer, it is slippery when new. Therefore, in order to fully exhibit the performance of the tire, the surface layer of the tread portion 1 must be worn to some extent. In the tire of the present invention, by providing the shallow groove 2 in the tread portion 1, the tread portion 1 is easily worn, so that the performance of a new tire can be exhibited at an early stage. Further, the drainage and traction properties are improved by the shallow groove 2, and the rubber of the tread portion 1 becomes easy to move at the time of ground contact, and by promoting heat generation, the grip performance can be exhibited at an early stage. Moreover, the appearance can be improved by the shallow groove 2.

  In the tire of the present invention, the width of the shallow groove 2 is 0.1 to 2.0 mm, preferably 0.5 to 1.5 mm. When the width of the shallow groove 2 is less than 0.1 mm, sufficient drainage may not be obtained. On the other hand, when the width exceeds 2.0 mm, the rigidity of the tread portion 1 is lowered and steering stability is deteriorated. Since the ground contact area is small, a sufficient grip may not be obtained. Here, the width w of the shallow groove 2 refers to the width of the opening in the cross section perpendicular to the extending direction of the shallow groove 2. Further, when the width of the shallow groove 2 changes in the extending direction of the shallow groove 2, the shallow groove 2 is the widest portion.

  The depth of the shallow groove 2 is 0.1 to 2.0 mm, preferably 0.2 to 0.5 mm. If the depth of the shallow groove 2 is less than 0.1 mm, sufficient drainage performance may not be obtained. On the other hand, if the depth is 2.0 mm or more, the rigidity of the tread portion 1 is lowered, and the steering is reduced. There is a risk that stability will deteriorate. Here, when the depth of the shallow groove 2 changes in the extending direction of the shallow groove 2, it means the deepest portion of the shallow groove 2. If a deep groove having a depth exceeding 2.0 mm is provided, uneven wear may occur, but such a problem does not occur in the tire of the present invention. The depth of the shallow groove 2 refers to the distance from the tread surface of the tread portion 1 to the groove bottom of the shallow groove 2 and does not include the protrusion provided on the groove bottom of the shallow groove 2. Here, the protrusions are those whose peripheral contour shape is circular, elliptical, or other curved shape, or parallelogram, rhombus, or other polygonal shape.

  In the tire of the present invention, the shallow groove 2 has a length of 50% or more, preferably 80% or more of the width of the tire ground contact surface, and all of the shallow grooves 2 extend to the tread end. However, it may be opened at the tread end, or only some of the shallow grooves 2 may be opened at the tread end. By setting it as such a structure, favorable initial drainage property can be obtained. The angle of the shallow groove 2 is preferably provided so as to be perpendicular to the input direction from the viewpoint of increasing the edge component. Note that a part or all of the shallow groove may be terminated about 20 mm before the tread end.

  Further, the shallow grooves 2 are arranged at intervals shorter than the length of the tire ground contact surface. Preferably, the shallow grooves 2 are always arranged in the ground plane so that there are two or more. By setting it as this range, the said effect can be acquired favorably. In the tire of the present invention, the shape of the shallow groove 2 is not particularly limited, and may be a straight shape extending along the tire width direction as shown in FIG. 1, but may be a zigzag shape or a corrugated shape. It may be. FIGS. 2A to 2I are schematic plan views showing examples of the shape of shallow grooves of a pneumatic tire for a motorcycle according to a preferred embodiment of the present invention. In the tire of the present invention, FIG. The shape of the shallow groove is not limited to these.

  2A is a shallow groove extending linearly in the tire width direction, FIG. 2B is a shallow groove extending zigzag in the width direction, and FIG. 2C is a wave shape in the width direction. (D) is a shallow groove extending in the tire width direction as a whole, although extending alternately in the width direction and the circumferential direction. 2 (e) shows shallow grooves extending linearly in a discontinuous manner in the width direction, and FIG. 2 (f) shows a plurality of shallow grooves formed in a substantially elliptical shape in the tire width direction. (G) is a shallow groove extending in the width direction as a whole, although both ends of the linear shallow groove extending in the width direction extend in the circumferential direction. Although it is a curved shape, it is a shallow groove extending in the width direction as a whole, and (i) is a shallow groove having branches at both ends of the shallow groove extending linearly in the width direction. The shapes of (g) and (h) have the advantage that they can be easily repelled by nails and the like.

  In the illustrated tire, there are three shallow grooves 2 in total, one in the center region Tc and two in the shoulder region Ts. However, the number of the shallow grooves 2 is limited to this. It is not a thing. In the tire of the present invention, the number of shallow grooves 2 may be greater in the center region Tc than in the shoulder region Ts of the tread portion 1, and may be greater in the shoulder region Ts than in the center region Tc. Good. That is, the distance between the shallow grooves 2 in the center region Tc and the shoulder region Ts may be different. If the number of shallow grooves 2 in the center region Tc is increased, the drainage performance is further improved, so that the grip performance on the wet road surface can be improved, and at the same time, the traction performance can be improved. On the other hand, if the number of the shallow grooves 2 in the shoulder region Ts is increased, the rubber in the shoulder region Ts can be easily moved at the time of ground contact, and the heat generation can be further promoted, whereby the grip performance can be further exhibited at an early stage. Furthermore, since the shoulder region Ts has fewer opportunities for ground contact than the center region Tc, by providing a shallow groove in the shoulder region Ts, an effect of improving the grip performance of the shoulder region Ts can be obtained. The drainage can be improved.

  Furthermore, in the tire of the present invention, the depth of the shallow groove 2 may be deeper in the center region Tc than in the shoulder region Ts of the tread portion 1, and in the shoulder region Ts than in the center region Tc. Also good. This is because when the depth of the shallow groove 2 in the center region Tc is increased, drainage and traction properties are further improved, so that grip performance on a wet road surface can be improved. This is because if the depth of the shallow groove 2 of Ts is increased, the rubber in the shoulder region Ts can be easily moved at the time of ground contact, and the grip performance can be further exhibited early by further promoting heat generation. For the same reason, the width of the shallow groove 2 may be wider in the center region Tc than in the shoulder region Ts of the tread portion 1, and may be wider in the shoulder region Ts than in the center region Tc. In the tire of the present invention, the depth of the shallow groove 2 does not have to be constant, and may vary along the width direction. For example, the center region Tc of the shallow groove 2 may be shallow and the shoulder region Ts deepened.

  Furthermore, in the tire of the present invention, it is preferable that the distance between the substantially parallel shallow grooves 2, in the illustrated example, L1 and L2 are 10 to 100 mm. Here, the space | interval of the shallow groove | channel 2 says the length of the surface of a tread part at the time of normal internal pressure and no load. If the distance between the substantially parallel shallow grooves 2 is less than 10 mm, the rigidity of the tread portion 1 is lowered, and the steering stability may be deteriorated. Moreover, since the area of the shallow groove 2 which occupies the whole grounding surface becomes large, there exists a possibility that grip performance may fall. On the other hand, if the distance between the shallow grooves 2 is greater than 100 mm, the drainage and traction properties deteriorate, and the tread portion 1 becomes difficult to move, so that the effects of the present invention may not be sufficiently obtained. In addition, when the shallow groove has a zigzag shape or the like, the interval between the intervals is the distance between the center positions of the swing width of the shallow groove.

  As described above, in the tire of the present invention, the depth of the shallow groove 2 may change in the extending direction. For example, the depth may be different at the position in the width direction of the tread portion 1. As described above, by appropriately adjusting the depth of the shallow groove 2, the drainage can be adjusted, and the grip performance can be adjusted by adjusting the rigidity of the tread portion.

  FIG. 3 is a schematic cross-sectional view showing an example of a change in depth in the extending direction of the shallow groove according to the pneumatic tire for a motorcycle of the present invention. FIG. 3A shows a shape in which the groove depth linearly decreases toward the outer side in the tire width direction, and FIG. 3B shows that the groove depth increases linearly toward the outer side in the tire width direction. It is a shape to go. (C) is a curved surface convex outward in the tire radial direction in the vicinity of the center of the groove bottom, and a curved surface concave inward in the tire radial direction in the vicinity of both sides of the groove bottom, forming a corrugated shape as a whole. ing.

  When the depth of the shallow groove 2 on the center region Tc side is increased, the drainage performance is further improved, so that the grip performance on the wet road surface can be improved. On the other hand, if the shoulder region Ts side of the shallow groove 2 is deepened, the rubber in the shoulder region Ts can move easily when touching the ground, and by further promoting heat generation, it is possible to further improve the grip performance at the time of turning and at the time of turning. Drainability can also be improved. In addition, the shallow part of the groove bottom of the shallow groove 2 becomes a standard for knowing the degree of wear of the tire.

  Furthermore, as described above, in the tire of the present invention, the width of the shallow groove 2 may change in the extending direction. For example, it is good also as a different width | variety in the position of the width direction of the tread part 1. FIG. As described above, the drainage can be adjusted by adjusting the width of the shallow groove 2 as appropriate, and the grip performance can be adjusted by adjusting the rigidity of the tread portion. In the tire of the present invention, the shape of the shallow groove 2 is not particularly limited. FIG. 4 is a schematic plan view showing an example of changes in the width of the shallow groove according to the pneumatic tire for motorcycles of the present invention. In the tire of the present invention, the shape of the shallow groove 2 is limited to these. It is not a thing.

  4A shows a shallow groove in which the groove width is widest in the middle portion and linearly narrows toward both ends of the shallow groove, and FIG. 4B shows the groove width that is narrowest in the middle portion. The shallow groove has a groove width that increases linearly as it goes to both ends of the shallow groove, and (c) is a shallow groove that gradually narrows at both ends of the shallow groove. (D) is a shallow groove with an elliptical middle portion and both ends are linear, (e) a shallow groove with a straight middle portion and both ends are elliptical, and (f) The middle portion is a straight groove and both end portions are shallow grooves having a substantially perfect circle shape. (G) is a shallow groove having a shape in which two elliptical shallow grooves are arranged in the extending direction. As shown in (e), (f), and (g), cracks can be prevented by providing no acute angle portions at both ends. The intermediate portion refers to an intermediate portion when the shallow groove is divided into three equal parts in the extending direction.

  If the shallow groove 2 is widened on the center region Tc side, the drainage performance is further improved, so that the grip performance on the wet road surface can be improved. On the other hand, if the shoulder region Ts side of the shallow groove 2 is widened, the rubber in the shoulder region Ts is easy to move at the time of ground contact, and by further promoting heat generation, the grip performance at the time of turning can be further improved. Drainability can also be improved.

  FIG. 5 is a schematic cross-sectional view showing an example of a cross-sectional shape in the groove width direction of the shallow groove according to the pneumatic tire for motorcycles of the present invention. In the tire of the present invention, the contour line 4 of the tread portion 1, a pair of groove walls 5 substantially perpendicular to the contour line 4, and a groove bottom substantially parallel to the contour line 4 connecting the pair of groove walls 5. 6 may be a shape different from the virtual cross-sectional shape composed of Here, the groove wall 5 and the groove bottom 6 may be connected vertically, or may be connected with a curve. That is, in the tire of the present invention, the cross-sectional shape of the shallow groove 2 is different from a general shape, and at least a part of the pair of groove walls 5 is tapered or in the depth direction of the shallow groove (tire radial direction). It may be a shape that narrows in stages. Moreover, the convex part 7 may be formed in the opening edge of the shallow groove | channel 2 of a tread part. Further, the groove wall 5 or the groove bottom 6 may be formed with unevenness extending in the extending direction of the shallow groove 2.

  5A, only the vicinity of the opening of the groove wall 5 has a tapered shape, and in FIG. 5B, the entire groove wall 5 has a tapered shape. Thus, by making the opening part of the shallow groove | channel 2 into a taper shape, drainage can be made more favorable, without impairing an edge effect. FIG. 5C shows a shape in which the width of the shallow groove 2 gradually decreases in the groove depth direction. With such a shape, the degree of wear of the tread portion 1 can be determined in stages. 5D and 5E show a shape in which the convex portion 7 is provided at the opening edge of the shallow groove 2, and FIG. 5D shows a shape that gradually rises as the opening edge of the shallow groove 2 is approached. (E) has a shape in which the opening edge of the shallow groove 2 swells substantially vertically. Thus, by providing the convex part 7 at the opening edge of the shallow groove 2, the contact pressure at the end of the shallow groove 2 is increased, and a better edge effect can be expected. In addition, an effect of improving visibility can be obtained. In this case, the height of the convex portion is made lower than the depth of the shallow groove. Furthermore, FIG.5 (f) has the shape where the front groove wall 5 is low and the back groove wall 5 is high with respect to the input direction. Thus, a favorable edge effect can be acquired by providing a step in the groove wall 5. 5 (g) and 5 (h) are shapes in which irregularities are provided on the groove bottom 6 and the groove wall 5, respectively. Thus, by providing a groove further inside the shallow groove 2, the visibility of the shallow groove 2 is improved. In addition, by providing irregularities on the groove bottom 6, since the irregularities on the groove bottom 6 appear after the shallow groove 2 is worn, the design is excellent. When the shallow groove has a tapered cross section, or when the groove wall 5 or the groove bottom 6 is provided with irregularities extending in the extending direction of the shallow groove 2, the depth of the shallow groove 2 is reduced. The reference is the outline 4 of the virtual cross-sectional shape, and the width of the shallow groove 2 is also based on the width of the opening of the virtual cross-sectional shape.

  In the tire of the present invention, a decoration pattern called serration in which a plurality of ridges are arranged at a predetermined pitch in the shallow groove 2 may be applied. In addition, the tread portion 1 may be provided with information such as a character or symbol such as a manufacturer name, or a pattern or a decoration pattern that can be used to understand the usage state of a figure or a camber angle in a shallow groove. Furthermore, when providing a circumferential shallow groove or a widthwise shallow groove inclined in the circumferential direction, these shapes may be an arrow shape and a rotation mark.

  In the tire of the present invention, it is only important that the shallow groove 2 formed in the tread portion 1 satisfies the above requirements, and there is no particular limitation other than that, and a known structure is adopted for other configurations. be able to. For example, as shown in the figure, when the main groove 3 is provided, the width and depth of the main groove 3 may be larger than the depth and width of the shallow groove 2. Moreover, there is no restriction | limiting in particular also about structures other than the tread part 1, A known structure is employable. FIG. 6 is a schematic cross-sectional view in the width direction of a pneumatic tire for a motorcycle according to a preferred embodiment of the present invention.

  The illustrated tire 10 of the present invention includes a tread portion 11, a pair of sidewall portions 12 connected to both sides of the tread portion 11, a pair of bead portions 13 respectively connected to the pair of sidewall portions 12, and each of these portions is a bead portion. 13 carcass 14 composed of carcass plies of at least one layer (one layer in the illustrated example) that reinforces each other. In the illustrated example, the end portion of the carcass 14 is folded and locked to the bead core 15 from the tire inner side to the outer side. However, the carcass 14 may be pinched and locked by bead wires from both sides.

  In the illustrated tire, a belt layer 16 is provided on the outer side of the carcass 14 in the tire radial direction. The belt cord of the belt layer 16 is not particularly limited, and a known non-extensible high elastic cord can be used. For example, aromatic polyamide (aramid, for example, trade name: Kevlar manufactured by DuPont) or polyethylene naphthalate ( PEN), polyethylene terephthalate (PET), organic fibers such as rayon and nylon, steel, glass fibers, carbon fibers and other materials can be appropriately selected and used. Such a belt may be composed of two or more inclined belt layers arranged so that the cord directions cross each other between the layers, and more than one layer whose cord direction is substantially the tire circumferential direction. It may consist of a spiral belt layer. In FIG. 6, a spiral belt layer 17 is provided outside the belt layer 16 in the tire radial direction.

  The tire of the present invention can be applied to both a front tire and a rear tire for a motorcycle, and can be applied to any tire having a radial structure and a bias structure.

Hereinafter, the present invention will be described in more detail with reference to examples.
<Example>
A pneumatic tire for a motorcycle having a tread pattern shown in FIG. 1 was produced with a tire size of 120 / 70ZR17M / C. The depth of the shallow groove is 0.3 mm, the width of the shallow groove is 1.0 mm, the angle of the shallow groove in the width direction is 0 ° with respect to the tire width direction, and a continuous groove having a constant groove width and groove depth. did. The cross-sectional shape of the shallow groove is composed of a pair of groove walls extending perpendicularly from the surface of the tread part, and a groove bottom that connects the groove walls and is substantially parallel to the tread part surface. The distance L1 between the shallow grooves was 30 mm, and L2 was 30 mm.

<Comparative example>
A comparative example tire was produced in the same manner as the example tire except that no shallow groove was provided in the tread portion.

  The obtained tires were evaluated for grip properties and traction properties according to the following procedures. The results are also shown in Table 1.

<Grip properties>
This was done by running on a wet road with a vehicle fitted with each tire. The grip performance was evaluated by the driver's feeling. At that time, the evaluation of the tire of the comparative example was set to 100, and the tire of the example was indexed.

<Traction characteristics>
Traction performance was evaluated based on driver feeling. At that time, the evaluation of the tire of the comparative example was set to 100, and the tire of the example was indexed.

  From Table 1, it can be seen that the tire of the present invention in which a predetermined shallow groove is provided in the tread portion is excellent in grip and traction.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Shallow groove 3a, 3b Main groove 4 Contour line 5 Groove wall 6 Groove bottom 7 Convex part 10 Pneumatic tire for motorcycles (tire)
DESCRIPTION OF SYMBOLS 11 Tread part 12 Side wall part 13 Bead part 14 Carcass 15 Bead core 16 Belt layer 17 Spiral belt layer

Claims (7)

In a pneumatic tire for a motorcycle having a tread portion formed in an annular shape,
A shallow groove having a width of 0.1 to 2.0 mm and a depth of 0.1 to 2.0 mm is provided in the tread portion in the tire width direction, and the length of the shallow groove is the width of the tire contact surface. A pneumatic tire for a motorcycle, characterized in that the tire is disposed at an interval that is equal to or greater than 50% of the tire and is shorter than the length of the tire contact surface.   The pneumatic tire for a motorcycle according to claim 1, wherein the number of the shallow grooves is greater in the center region than in the shoulder region of the tread portion.   The pneumatic tire for a motorcycle according to claim 1, wherein a depth of the shallow groove is deeper in a center region than in a shoulder region of the tread portion.   The pneumatic tire for a motorcycle according to claim 1, wherein a width of the shallow groove is wider in a center region than in a shoulder region of the tread portion.   The pneumatic tire for a motorcycle according to claim 1, wherein the number of shallow grooves is greater in a shoulder region than in a center region of the tread portion.   The pneumatic tire for a motorcycle according to claim 1, wherein a depth of the shallow groove is deeper in a shoulder region than in a center region of the tread portion.   The pneumatic tire for a motorcycle according to claim 1, wherein a width of the shallow groove is wider in a shoulder region than in a center region of the tread portion.

Images