WO2019108173A1

WO2019108173A1 - Tire sipe design for aggression resistance

Info

Publication number: WO2019108173A1
Application number: PCT/US2017/063677
Authority: WO
Inventors: Paul Andrew MAYNI
Original assignee: Compagnie Generale Des Etablissements Michelin
Priority date: 2017-11-29
Filing date: 2017-11-29
Publication date: 2019-06-06

Abstract

A tread for a heavy truck tire having a shoulder rib (38) with a lateral outer surface (32) is provided. A circumferential groove (54) is next to the shoulder rib (38) in a lateral direction, and a sipe (56) is located in the shoulder rib (38). The sipe (56) has a narrow width portion (52) and a teardrop (18). A transition zone (20) extends from the teardrop (18) to an opening (42) located at the lateral outer surface (32). A transition location (44) is at the engagement of the transition zone (20) and the teardrop (18), and an inner surface (58) of the shoulder rib (38) defines a smooth transition from the teardrop (18) to the transition zone (20) across the transition location (44).

Description

TIRE SIPE DESIGN FOR AGGRESSION RESISTANCE

HELD OF THE INVENTION

[0001] The subject matter of the present invention relates to sipes for tires that feature a teardrop and a transition zone that minimize or avoid stress concentrations to in turn reduce aggression at the sipe. More particularly, the present application involves a transition zone to teardrop interface that is smooth and eliminates ridges or other areas of stress concentration.

BACKGROUND OF THE INVENTION

[0002] Tires normally include tread that has a series of ribs that extend in a circumferential direction of the tire separated in the axial direction by grooves. The ribs can be provided with a series of sipes that function to improve traction in certain road conditions. The sipes are thin slits cut into the ribs and can be made in a variety of manners. For instance, the shape along the lengths of the sipes may be straight, zigzagging, undulating, or angled into the tire elements. The sipe depths may also vary or be consistent along their lengths, and may extend into the tread all the way to the end of life tread depth. The sipes may close within the tire“footprint” on the road, and can increase the flexibility of the tread block into which the sipes are located. The presence of sipes can improve stopping distance, breakaway traction, and rolling traction on glare ice. Additionally sipes have been found to improve traction for tires in snow, mud, and other types of ice.

[0003] It is known to provide sipes with a teardrop shape that tends to increase traction of the tire when the tire is near the end of its life. The teardrop feature in the sipe is an increase in the circumferential length of the sipe at an area of the sipe closer to the center of the tire in the radial direction. This increase in circumferential length causes the sipe to have a larger void radially closer to the tire center than portions of the sipe radially farther form the tire center. When the tire tread wears down, the larger void portion will open up and be exposed to the road surface and will improve traction and water removal when the tire is nearing the end of its life.

[0004] Although the inclusion of sipes helps improve tire performance in certain areas, the addition of these cut features into the ribs of the tire may also cause a risk of irregular wear on the ribs, increased rolling resistance, degradation in sculpture robustness, and a risk of increased chipping and chunking. Sipes that are present in shoulder ribs of heavy commercial truck tires may cause irregular wear and sipe aggression. Sipe aggression is the cracking or breaking of the shoulder rib due to a stress concentration caused by the sipe. Teardrop shapes can be used to reduce this stress concentration, but the geometries used do not allow for a smooth transition zone from the edge of the sipe teardrop through a blending zone on the shoulder of the tire.

[0005] Another way to address the problem of sipe aggression is to both include a tear drop feature into the sipe at the shoulder and to increase the diameter of the teardrop. However, this design only addresses the stress concentration associated with bending along the length of the sipe. Regardless of the teardrop diameter the interaction with the shoulder region of the tire is poor and still results in cracking at the sipe at the shoulder of the tire. Fig. 1 shows one example of a sipe 56 that has a teardrop 18 open at the side of the tire 10. A transition zone 20 extends from a flat ridge 30 that completely surrounds the teardrop 18 to the first lateral outer surface 32. The transition zone 20 is shaped like a hexagon and Applicants theorize that cracks appear in this transition zone 20 due to the sharp edges that are present at the ridge 30 and transition zone 20 that create a stress concentration. Another design is shown in Fig. 2 in which the teardrop 18 is located within a pocket 22 and is circular in shape. The pocket 22 is a depression on the first lateral outer surface 32 so that some of the surface 32 is located outward/outboard in the lateral direction 28, and so that some of the surface 32 is located more inward/inboard in the lateral direction 28. A ridge 30 that is flat completely surrounds the teardrop 18, and the transition zone 20 extends from the ridge 30 to the first lateral outer surface 32 and has a convex shape with a single radius that extends along the lower half of the ridge 30. The upper half of the ridge 30 next to the teardrop 18 has no such transition zone 20 element. Applicants theorize that cracks develop at the transition zone 20 and ridge 30 due to the sharp radius and edge that create a stress concentration in this design.

[0006] Fig. 3 illustrates two additional designs of transition zones 20 associated with teardrops 18 at the bottom of sipes 56 that open onto the first lateral outer surface 32 of the tread 16. The transition zone 20 on the sipe 56 on the left hand side is not located in a pocket 22 and features a constant radius from the teardrop 18 to the first lateral outer surface 32 with a flat ridge 30 located between the teardrop 18 and the transition zone 20. The teardrop 18, ridge 30 and the transition zone 20 are all oval racetrack in shape. The teardrop 18 on the right hand side of Fig. 3 is likewise oval racetrack in shape, the ridge 30 is present, and its transition zone 20 extends to the first lateral outer surface 32 in the pocket 22. The transition zone 20 is generally in the shape of a rectangle with the teardrop 18 not centered in the middle of the rectangle. The flat ridges 30, as with those in the Figs. 1 and 2 embodiments, create a stress concentration located at the teardrops 18 and transitions zones 20 that lead to cracking. Although various ways of constructing sipes 56 with teardrops 18 are known, there remains room for variation and improvement within the art.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:

[0008] Fig. 1 is a perspective view of sipe with a ridge and a transition zone in the shape of a hexagon.

[0009] Fig. 2 is a perspective view of a sipe with a ridge and a transition zone that extends partially around the teardrop.

[0010] Fig. 3 is a perspective view of sipes with oval racetrack shaped teardrops and ridges and transition zones of different configurations.

[0011] Fig. 4 is a front view of a tire that includes sipes and pockets.

[0012] Fig. 5 is a side view of a portion of a tire that has a sipe with a transition zone in accordance with one exemplary embodiment.

[0013] Fig. 6 is a top view of the portion of the tire of Fig. 5.

[0014] Fig. 7 is a cross-section view taken along line 7-7 of Fig. 5.

[0015] Fig. 8 is a perspective view of the portion of the tire of Fig. 5.

[0016] Fig. 9 is a cross-section view of a sipe with a transition zone in accordance with another exemplary embodiment.

[0017] Fig. 10 is a side view of a portion of a tire that has a sipe with a teardrop and opening that have different cross-sectional shapes in accordance with another exemplary embodiment.

[0018] Fig. 11 is a graph of maximum principle stress vs. angular position upon comparing tires that do and do not have a transition zone. [0019] Fig. 12 is a graph of maximum principle strain vs. angular position upon comparing tires that do and do not have a transition zone.

[0020] The use of identical or similar reference numerals in different figures denotes identical or similar features.

DETAILED DESCRIPTION OF THE INVENTION

[0021] Reference will now be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, and not meant as a limitation of the invention. For example, features illustrated or described as part of one embodiment can be used with another embodiment to yield still a third embodiment. It is intended that the present invention include these and other modifications and variations.

[0022] The present invention provides for a sipe 56 design for aggression resistance. The sipe 56 includes a teardrop 18, and a transition zone 20 from the teardrop 18 to an outer surface 32 of the tread 16. The teardrop 18 and transition zone 20 are arranged as a smooth feature so that stress concentrations are avoided or minimized. In particular, the engagement between the teardrop 18 and the transition zone 20 is a smooth transition without any sharp edges or ridges 30. In some instances, the transition zone 20 is in the shape of a trumpet bell. An opening 42 of the transition zone 20 can be circular in shape.

[0023] Fig. 4 shows a tire 10 that is a heavy duty truck tire 10. In this regard, the tire 10 is not designed for nor used with a car, motorcycle, or light truck (payload capacity less than 4,000 pounds), but is instead designed for and used with heavy duty trucks such as 18 wheelers, garbage trucks, or box trucks. The tire 10 may be a steer tire, a drive tire, a trailer tire, or an all position tire. The tire 10 includes a casing 12 onto which a tread 16 is disposed thereon. The central axis 14 of the tire 10 extends through the center of the casing 12, and the lateral/axial direction 28 of the tire 10 is parallel to the central axis 14. The radial direction 24 of the tire 10 is perpendicular to the central axis 14, and the tread 16 is located farther from the central axis 14 in the radial direction 24 than the casing 12. The tread 16 extends all the way around the casing 12 in the circumferential direction 26 of the tire 10 and circles the central axis 14 360 degrees.

[0024] The tread 16 features five ribs that are separated by four longitudinal grooves that extend in the circumferential direction 26. The five ribs can be classified as a central rib, two intermediate ribs, and two shoulder ribs 38 and 40. The first shoulder rib 38 is located on one side of the tread 16 in the lateral direction 28, and the second shoulder rib 40 is located on an opposite side of the tread 16 in the lateral direction 28. A first lateral outer surface 32 is present at the first shoulder rib 38 and is the outer most surface of the tread 16 in the lateral direction 28. On an opposite side of the tread 16 in the lateral direction 28 a second lateral outer surface 34 on the second shoulder rib 40 is present. The ribs can each be made up of a number of tread blocks 60 that can have various shapes, sizes, and structural features to cause the tread 16 to have different performance properties. The tread 16 may include certain structural features that can reduce abnormal wear. One such structural feature shown with reference to Fig. 4 may be sipes 56 that extend across the tread blocks 60 of the ribs in the lateral direction 28. The sipes 56 are thin grooves/cuts in the tread blocks 60. The sipes 56 may have widths that are two millimeters or less. When a teardrop 18 is included in the sipe 56, the width of the teardrop 18 may be less than two millimeters or may be greater than or equal to two millimeters. The rolling tread width 36 of the tread 16 is the area of the tread 16 that contacts the ground during use of the tire 10, and the rolling tread width 36 extends between the first and second lateral outer surfaces 32, 34 in the lateral direction 28. The outer surfaces 32, 34 do not engage the ground when the tire 10 is used and are not within the rolling tread width 36 but rather define its footprint. Pockets 22 are another feature of the tire 10 illustrated in Fig. 4 and are indentations in the lateral surfaces 32, 34 such that the lateral surfaces 32, 34 extend somewhat inboard and outboard in the lateral direction 28 and are not flat planar surfaces along their entire lengths in the circumferential direction 26.

[0025] The sipes 56 located in the shoulder rib 38 are located within the pockets 22 of the shoulder rib 38, but need not be in the pockets 22 in accordance with other exemplary embodiments. The pockets 22 are present in some arrangements and not in others, and even if present the sipes 56 may be within the pockets 22, outside of the pockets 22, or partially within and outside of the pockets 22. The sipes 56 are open both at the upper surface 50 of the shoulder rib 38, and at the first lateral outer surface 32. The opening of the sipes 56 at the first lateral outer surface 32 is larger than the opening of the sipes 56 at the upper surface 50. The openings of the narrow width portion 52 of the sipes 56 at the first lateral outer surface 32 are generally rectangular in shape. However, the opening of the narrow width portion 52 could be variously shaped in other versions of the tire 10 such as being zig-zag, sinusoidal, curved, or irregular shaped in other embodiments.

[0026] Figs. 5-8 illustrate an exemplary embodiment of the tread 16 in which the sipe 56 exhibits aggression resistance. The sipe 56 is located in a tread block 60 of the tread 16 present in a shoulder rib 38. The shoulder rib 38 is at the edge of the tread 16 in the lateral direction 28. The sipe 56 includes a narrow width portion 52 that extends from the upper surface 50 into the tread block 60 to a teardrop 18 located within the tread block 60. The narrow width portion 52 extends all the way across the shoulder rib 38 in the lateral direction 28 and has a width that extends in the circumferential direction 26. The narrow width portion 52 is open at the upper surface 50, the first lateral outer surface 32, and at the surface of the shoulder rib 38 that directly faces the circumferential groove 54. The narrow width portion 52 is linear in shape, but could be wavy, angled, curved, or variously shaped in accordance with other designs of the sipe 56. The teardrop 18 is circular in shape and is located inward in the radial direction 24 from the narrow width portion 52. The narrow width portion 52 opens into the teardrop 18 so that they form a continuous opening from one to the other. The teardrop 18 extends along the majority of, but not all of the length of the shoulder rib 38 in the lateral direction 28. The teardrop 18 does not extend to the first lateral outer surface 32 of the shoulder rib 38, but does extend to the opposite side of the shoulder rib 38 so that it opens into circumferential groove 54.

[0027] The teardrop 18 is shown as having a circular cross-section shape with a single diameter size along its entire length in the lateral direction 28, and as extending only in the lateral direction 28. However, the diameter, cross-section, and orientation of extension can be different in other embodiments. For example, the cross-sectional shape of the teardrop 18 may be more teardrop in shape than circular in shape. Also, the teardrop 18 need not have the same cross-sectional shape or dimensions along its entire length in the lateral direction 28. The teardrop 18 is wider than the narrow width portion 52 such that the teardrop 18 extends a greater distance in the circumferential direction 26 than does the narrow width portion 52.

[0028] The teardrop 18 opens into the transition zone 20 which in turn defines an opening 42 on the first lateral outer surface 32. The opening 42 is spaced from the upper surface 50 in the radial direction 24. The junction of the transition zone 20 and the teardrop 18 is denoted as a transition location 44 and is a smooth continuous engagement with no discontinuity present that could cause a stress concentration. A ridge 30 is not present at the transition location 44, and is not present in other locations of the teardrop 18 or the transition zone 20 such that no ridge 30 is present from the teardrop 18 to the opening 42. The transition location 44 may be the same shape as the cross-section of the teardrop 18 at the intersection with the transition zone 20. The voids created by the teardrop 18 and the transition zone 20 are smooth such that there is no discemable parting line, ridge 30, or other discontinuity at the transition location 44, and the inner surface of the shoulder rib 38 is smooth when moving across the teardrop 18 past the transition location 44 and across the transition zone 20. The shoulder rib 38 has an inner surface 58 that defines the narrow width portion 52, the teardrop 18, the transition zone 20, and any other portion of the sipe 56. This inner surface 58 can define a smooth transition from the teardrop 18 across the transition location 44 to the transition zone 20 so that a discontinuity that causes stress concentrations to occur is not present.

[0029] The sipe 56 opens up into the transition zone 20 and is located at the transition location 44 as well. The opening the sipe 56 defines across the transition location 44 and the transition zone 20 to the first lateral outer surface 32 is continuous such that a single void is defined through the sipe 56 and into the transition zone 20.

[0030] The transition zone 20 is in the shape of a trumpet bell and increases in size from the transition location 44 to the opening 42. With reference to Fig. 7, the wall of the shoulder rib 38 that defines the transition zone 20 has a convex surface 48 that extends from and engages the transition location 44. Moving in the lateral direction 28, the wall of the shoulder rib 38 then transitions into a concave surface 46 that is located closer to the opening 42 than the convex surface 48. The very end of the wall of the shoulder rib 38 located at the opening 42 may be part of the concave surface 46, or the concave surface 46 can end thus causing the very end of the wall of the shoulder rib 38 at the opening 42 to be straight in the lateral direction 28 such that the transition zone 20 does not become larger from the concave surface 46 to the opening 42. In some instances, the transition zone 20 will always widen or become larger upon extension from the transition location 44 to the opening 42 at all times so that at no time does it remain the same size.

[0031] The convex surface 48 has a radius of curvature that may be the same as, greater than, or less than the radius of curvature of the concave surface 46. The magnitudes of the radii of curvature can be the same along the entire convex surface 48/concave surface 46, or the surfaces 46, 48 can have different radii at different locations along their lengths. The opening 42 is circular in shape and opens only through the first lateral outer surface 32 and not into the casing 12 or the circumferential groove 54.

[0032] The sipe 56 with the teardrop 18, transition zone 20, and opening 42 is located in the shoulder rib 38 at the first lateral outer surface 32 of the tire 10. However, it is to be understood that a similar sipe 56 with teardrop 18, transition zone 20 and opening 42 can be located at the second shoulder rib 40 on the other side of the tire 10 at the second lateral outer surface 34. There can be any number of sipes 56 with the aforementioned features around the tread 16 along the entire circumferential length of the tread 16 in the circumferential direction 26. The sipes 56 with the transition zones 20, teardrops 18, and openings 42 may in some instances be located only within the shoulder ribs 38, 40 and not within any other ribs of the tire 10 such as the center rib, or intermediate ribs. If a sacrificial rib is present in the tire 10, the sacrificial rib may include the sipes 56 with the transition zones 20, teardrops 18, and openings 42 while the rib next to the sacrificial rib does not include the sipes 56, transition zones 20, teardrops 18 and openings 42. However, in some arrangements even if a sacrificial rib is present, it may or may not include the sipes 56, transition zones 20, teardrops 18 and openings 42, and the rib next to the sacrificial rib can be defined as the shoulder rib 38 or 40 and this shoulder rib 38 or 40 may or may not include the sipes 56 with the transition zones 20, teardrops 18 and openings 42.

[0033] The sipes 56 with the transition zones 20, teardrops 18 and openings 42 can be included on tread 16 that is a retread band that is subsequently attached to a casing 12 and formed into a tire 10. Alternatively, the sipes 56 with the transition zones 20, teardrops 18, and openings 42 may be formed or provided with original tires 10 that are not formed with retread bands.

[0034] Fig. 9 is a cross-sectional view of another embodiment of the sipe 56 showing the teardrop 18 and the transition zone 20. The transition zone 20 differs from other embodiments in that it is not defined by a concave surface 46 of the wall of the shoulder rib 38, but rather includes only a single convex surface 48. The single convex surface 48 extends from the transition location 44 all the way to the opening 42. The single convex surface 48 has different radii of curvature along its length so that the transition zone 20 widens at different rates in the direction of extension in the lateral direction 28 from the teardrop 18 to the opening 42. In other embodiments, the convex surface 48 has a single radius of curvature so that the transition zone 20 has a different look than that illustrated with reference to Fig. 9. The opening 42 may again be circular in shape in the Fig. 9 embodiment. The other features of the sipe 56, teardrop 18, transition zone 20, tire 10, and shoulder rib 38 may be the same as in previous embodiments and a repeat of these features and variations need not be repeated.

[0035] Another embodiment of the tire 10 is shown with reference to Fig. 10 that shows a side view of the tire 10 with a sipe 56 that has a narrow width portion 52 that is zig-zag in shape. As stated, the narrow width portion 52 can be variously shaped in other exemplary embodiments. The teardrop 18 is not circular in cross-sectional shape, but instead has a generally rectangular cross-sectional shape with comers that are fillets and an upper section that slopes inward to the narrow width portion 52 having both concave 46 and convex 48 surfaces. The opening 42 at the first lateral outer surface 32 is circular in cross-sectional shape. The transition zone 20 transitions from the generally rectangular shape of the teardrop 18 to the circular shape of the opening 42 in a smooth manner. Further, the transition location 44 lacks a step or other discontinuity so that a smooth transition occurs from the teardrop 18 to the transition zone 20 in the lateral direction 28. Although shown in Fig. 10 as having a circular cross-sectional shape, the opening 42 could have the same cross-sectional shape as the teardrop 18 or could have yet different cross-sectional shape in accordance with other embodiments. The teardrop 18 shape could be non-uniform and transition to a non-uniform shaped opening 42, or the teardrop 18 could be non-uniform and transiotn to a uniform shaped opening 42.

[0036] The transition location 44 is smooth and eliminates or minimizes discontinuities between the teardrop 18 and the transition zone 20 to in turn minimize or eliminate aggression at the sipes 56. The openings 42, teardrops 18 and narrow width portions 52 in the embodiments shown are not located in pockets 22, but could be in pockets 22 in other embodiments. The transition zone 20 may have a circular cross- section shape along its entire length in the lateral direction 28 from the transition location 44 to the opening 42, although the diameter of the circular cross-section may change along its length in the lateral direction 28. The geometry of the sipe 56 having the teardrop 18 and transition zone 20 can be achieved by 3D printing technology or any other molding technology capable of generating complex 3D shapes. In as much as the presence of the narrow width portion 52 causing a stress concentration or other discontinuity due to its opening into the transition zone 20 or the teardrop 18, it is to be understood that the transition from the teardrop 18 to the transition zone 20 lacks a discontinuity so that even if this other feature from the narrow width portion 52 causes a stress concentration, the presently disclosed arrangement still minimizes or eliminates the stress concentration brought about by the aforementioned transition to result in less or no aggression damage.

[0037] Figs. 11 and 12 show results of a test carried out in accordance with one exemplary embodiment. The test compares a“Trumpet” design in which the teardrop 18 is circular in cross-sectional shape with an opening 42 that is circular in cross-sectional shape with a larger diameter than the teardrop 18 and having the transition zone 20, to a “No Trumpet” design in which the teardrop 18 is circular and that extends all the way to the lateral outer surface 32 without the inclusion of a larger diameter opening 42 or transition zone 20. The X axis of the graphs shows different locations of the tires 10 as they roll through the contact patch and experience forces thereon. These are different angular positions that reflect the tire 10 azimuth through rotation where 180 degrees is when the tire is in the contact patch. The Y axis of the graph of Fig. 11 shows the maximum principle stress of any particular point of the tire 10 in units of daN/mm². The Y axis of the graph of Fig. 12 shows the maximum principle strain of any particular point of the tire 10, which is a dimensionless quantity. The points that are looked at are those that extend from the transition location 44 to the opening 42 on the inner surface 58 of the “Trumpet” tire 10, and the equivalent depth from the lateral outer surface 32 inward on the inner surface 58 of the“No Trumpet” tire 10. As shown, the maximum stress and strain of the“Trumpet” tire 10 is less than that of the“No Trumpet” tire 10 at a majority of , but not all of, the angular positions of the tire 10 relative to the contact patch.

[0038] While the present subject matter has been described in detail with respect to specific embodiments and methods thereof, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing may readily produce alterations to, variations of, and equivalents to such embodiments. Accordingly, the scope of the present disclosure is by way of example rather than by way of limitation, and the subject disclosure does not preclude inclusion of such modifications, variations and/or additions to the present subject matter as would be apparent.

Claims

CLAIMS What is claimed is:

1. A tread for a heavy truck tire, comprising:

a shoulder rib having a lateral outer surface;

a circumferential groove next to the shoulder rib in a lateral direction; and a sipe located in the shoulder rib, wherein the sipe has a narrow width portion and a teardrop, wherein a transition zone extends from the teardrop to an opening located at the lateral outer surface, wherein a transition location is at the engagement of the transition zone and the teardrop, and wherein an inner surface of the shoulder rib defines a smooth transition from the teardrop to the transition zone across the transition location.

2. The tread as set forth in claim 1, wherein the transition location lacks a ridge that has a flat surface.

3. The tread as set forth in claim 1 or 2, wherein the transition zone is in the shape of a trumpet bell.

4. The tread as set forth in any one of claims 1-3, wherein the transition zone does not contract in size at any point upon extension from the transition location to the opening.

5. The tread as set forth in any one of claims 1-4, wherein the inner surface has a convex surface that extends from the transition location towards the opening in the lateral direction and that defines a portion of the transition zone, wherein the inner surface has a concave surface that engages the convex surface and extends from the convex surface towards the opening in the lateral direction and defines another portion of the transition zone.

6. The tread as set forth in claim 5, wherein the inner surface has a straight surface that engages the concave surface and extends from the concave surface towards the opening in the lateral direction and ends at the opening.

7. The tread as set forth in any one of claims 1-4, wherein the inner surface has a convex surface that extends from the transition location towards the opening in the lateral direction and ends at the opening, wherein the convex surface defines the entire transition zone, wherein the entire inner surface from the transition location to the opening is convex in shape.

8. The tread as set forth in any one of claims 1-7, wherein the cross-sectional shape of the transition zone at all locations from the transition location to the opening in the lateral direction is circular.

9. The tread as set forth in any one of claims 1-8, wherein the teardrop has a circular cross-sectional shape.

10. The tread as set forth in any one of claims 1-9, wherein the narrow width portion extends to and opens into the transition zone.

11. The tread as set forth in any one of claims 1-10, wherein the narrow width portion extends to the lateral outer surface, wherein the narrow width portion extends to and opens into the opening such that the narrow width portion is open on the lateral outer surface from the opening to an upper surface of the shoulder rib.

12. The tread as set forth in any one of claims 1-11, wherein the sipe opens into the circumferential groove.

13. The tread as set forth in any one of claims 1-12, wherein the shoulder rib is not a sacrificial rib of the tread

14. The tread as set forth in any one of claims 1-13, wherein the tread is a retread band.

15. The tread as set forth in claim 1, wherein the cross-sectional shape of the teardrop at the transition location is different than the cross-sectional shape of the opening at the lateral outer surface.