Patent Description:
Tire treads generally extend about the outer circumference of a tire to operate as the intermediary between the tire and a surface upon which it travels (the operating surface). Contact between the tire tread and the operating surface occurs along a footprint of the tire. Tire treads provide grip to resist tire slip that may result during tire acceleration, braking, and/or cornering. Tire treads may also include tread elements, such as ribs or lugs, and tread features, such as grooves and sipes, each of which may assist in providing target tire performance when a tire is operating under particular conditions. Documents <CIT> and <CIT> each discloses a tire with improved grip.

One problem with treads for drive tires is the compromise between traction, rolling resistance and wear / abnormal wear.

It is known that adding sipes in a tire rib can improve wear rate and traction, but it has not been used successfully in the shoulder ribs of drive tires for the long-haul trucking application because it often triggers abnormal wear. The shoulders of long-haul drive tires are therefore typically designed with solid ribs, with no full-width transverse sipes or full-depth transverse grooves. As a result, the design of long-haul drive tire treads is sacrificing shoulder rib wear rate and traction in order to avoid abnormal wear.

It is also known that the provision of inclined sipes improve the tire's irregular wear performance, but it is not known whether this inclination coupled with other features helps or hurts irregular wear performance. This inclination is in the "negative" direction in that the sipe is angled away from the contact patch, from the bottom to the top of the sipe, as the tire rotates. <FIG> shows the rolling direction RD and the orientation of the lateral sipe <NUM> in relation to the rolling direction RD. However, even the provision of inclined sipes in the shoulder rib has been avoided, because as stated the inclusion of a sipe in the shoulder rib increases the risk of abnormal wear. Further, the combination of sipe inclination with other geometric features of the sipe used in the shoulder rib is not known or understood. As such, there remains room for variation and improvement within the art. These problems are solved by a tire according to claim <NUM>.

The use of the same or similar reference numerals in the figures denotes the same or similar features.

Reference will now be made in detail to embodiments of the invention, examples of which are illustrated in the drawings. These examples are provided by way of explanation of the invention.

As shown in <FIG>, a heavy truck tire <NUM> generally comprises a crown portion C connected by respective sidewalls SW, SW' to beads portions L, L'. The crown portion comprises a tread <NUM> according to an embodiment of the invention. The design of the tread <NUM> is substantially symmetric, that is to say that the tread features are arranged substantially symmetrically about the center plane of the tread <NUM>. This tread <NUM> is said to be of a directional design because it has a different appearance according to which side it is oriented. A directional tire or tread does not only look differently but it also performs differently if used in one rolling direction or the other. This is why directional treads or tires conventionally bear markings that indicate the designed rolling direction. Such markings may take the form of arrows pointing in the designed rolling direction. Also as used in the present application, the notation RD may be used instead of an actual marking on the tread or tire, simply an indication of the rolling direction of the tread or tire. Using the tire for rolling in the opposite direction would be detrimental to its best performance.

<FIG> is a magnified and flattened projection view of a portion of the tread <NUM> of <FIG>. As shown in <FIG>, the tread <NUM> has a longitudinal direction X (also referred to as the circumferential direction of the tire), a lateral direction Y (also referred to as the axial or transverse direction) and a thickness direction Z (also referred to as the tread depth direction, and also referred to as a radial direction). It is to be understood that as used herein, the thickness direction Z and the radial direction Z are interchangeable and mean the same thing, and that that longitudinal direction X and the circumferential direction X are interchangeable and mean the same thing, and that the lateral direction Y and the axial direction Y and the transverse direction Y are interchangeable and mean the same thing.

The tread depth is generally defined as the distance between the tread contact surface and a translation of this contact surface to be tangent to the deepest features in the tread.

The tread <NUM> has respective tread edge limits <NUM>, <NUM>' on each side and longitudinal ribs <NUM> defined by longitudinal grooves <NUM> separating the ribs <NUM>. The tread edge limits <NUM>, <NUM>' are straight lines running in the longitudinal direction X around the tire <NUM> positioned at the outboard most locations in the lateral direction Y of the rolling tread width (RTW) that engage the ground. However, the tread edge limits <NUM>, <NUM>' do not include the sacrificial rib if the tire <NUM> does in fact have one or more sacrificial ribs at the tread edges. Longitudinal grooves <NUM> may be straight or undulate along their main direction as represented in the FIGS. The tread <NUM> has shoulder areas <NUM>, <NUM>' that extend inboard in the lateral direction Y from their respective tread edge limits <NUM>, <NUM>'. The shoulder areas <NUM>, <NUM>' may in some exemplary embodiments be defined as extending inboard in the lateral direction Y from the tread edge limits <NUM>, <NUM>' each ranging up to <NUM>% of the rolling tread width (RTW). If the tread <NUM> is designed with shoulder ribs <NUM>, then the shoulder area <NUM>, <NUM>' may be instead the shoulder ribs <NUM>. Various exemplary embodiments will be described in which the shoulder area <NUM>, <NUM>' is in fact the shoulder rib <NUM>, but it is to be understood that certain designs of the tread <NUM> exist in which shoulder ribs <NUM> and the associated shoulder grooves <NUM> are not present in the shoulder areas <NUM>, <NUM>'. The ribs <NUM> defined between the respective shoulder grooves <NUM>, <NUM>' and tread edge limits <NUM>, <NUM>' are referred to as shoulder ribs <NUM>. The shoulder grooves <NUM>, <NUM>' are the two most outboard longitudinal grooves <NUM> of the tread <NUM> in the axial direction Y, and are thus the two longitudinal grooves <NUM> closest to the two tread edge limits <NUM>, <NUM>'. Shoulder areas <NUM>, <NUM>' are solid ribs comprising lateral sipes <NUM>, <NUM>' running across them and connecting the shoulder grooves <NUM>, <NUM>' to the tread edge limits <NUM>, <NUM>'. Although in other embodiments the lateral sipes <NUM>, <NUM>' need not extend the entire way from the tread edge limits <NUM>, <NUM>' to the shoulder grooves <NUM>, <NUM>' and need not terminate at either one of or both of these features <NUM>, <NUM>' and <NUM>, <NUM>'. A sipe is the narrow space formed in a tread between walls of material over a depth at most equal to the tread depth, said walls being able, at least in part, to come into contact with one another in the usual running conditions of the tire. Sipes are generally made as thin as manufacturing would reasonably allow, most of the time under <NUM> and preferably at around <NUM>. In some instances, the sipes <NUM>, <NUM>' are up to <NUM> in thickness. Sipes <NUM>, <NUM>' are full depth sipes. Sipes are said to be full depth sipes when their average depth is at least <NUM>% of the tread depth. In some versions of the tread <NUM> a mixture of sipes <NUM>, <NUM>' can be present that do not extend to at least <NUM>% of the tread depth, and that do extend to at least <NUM>% of the tread depth.

As shown on the left side of <FIG>, an interior shoulder zone ISZ of the shoulder area <NUM> is defined as an area that is from <NUM>% of the rolling tread width (RTW) to <NUM>% of the rolling tread width (RTW) from the tread edge limit <NUM>. The outer boundary line OBL is a longitudinal straight line running at a distance of <NUM> from the tread edge limit <NUM>. Sipe point A is the location of the lateral sipe <NUM> that intersects the OBL, and sipe point B is the location in the ISZ of the lateral sipe <NUM> farthest from sipe point A in the longitudinal direction X such lateral distance being designated as maximum distance D.

As an example of measurement, the tread edge limit <NUM> is a straight edge such that it does not have any variation at the outer surface <NUM> of the shoulder area <NUM> in the lateral direction Y. The OBL is thus measured <NUM> in the lateral direction Y from the tread edge limit <NUM> as noted in <FIG>. The RTW can be measured to be <NUM>, and <NUM>% of this number is <NUM>, and <NUM>% of this number is <NUM>. The ISZ is therefore a zone in the lateral direction Y that is from <NUM> to <NUM> from the tread edge limit <NUM>. As shown, the lateral sipes <NUM> extend from the tread edge limit <NUM> in the lateral direction Y past the OBL and to the shoulder groove <NUM> where they terminate. Since the shoulder groove <NUM> defines a limit to the inboard extent of the lateral sipe <NUM>, any sipe on the other side of the shoulder groove <NUM> is not counted as part of the lateral sipe <NUM> that is between the shoulder groove <NUM> and the tread edge limit <NUM>. The lateral sipe <NUM> at the OBL is designated as sipe point A. The maximum distance D of the lateral sipe <NUM> in the ISZ from sipe point A is noted. This location of the lateral sipe <NUM> in the ISZ is noted as sipe point B and is located at the shoulder groove <NUM> in the embodiment shown in <FIG>. The average sipe angle (αA) can thus be measured for tread <NUM> with or without shoulder grooves <NUM>, or any grooves <NUM>.

The orientation of a lateral sipe <NUM> is defined by its angle α relative to the lateral direction Y. A certain angle α can be measured in any location along the sipe <NUM>. This local angle α can be a constant value in the case of a straight sipe <NUM> but α can also vary significantly along the length of the sipe <NUM>. To characterize the main orientation of the sipe <NUM>, an average sipe angle αa is defined in the shoulder area <NUM>. The average sipe angle αa is defined as the angle relative to the lateral direction Y of a straight line connecting the point (A) where the lateral sipe <NUM> intersects the OBL, and the point (B) that is where the lateral sipe <NUM> from <NUM>%-<NUM>% in the lateral direction Y is located farthest from the lateral sipe <NUM> at the OBL (point A) in the longitudinal direction X. According to the invention, this average angle is greater than <NUM>° and preferably less than <NUM>° in absolute value. Using absolute value to characterize an angle is a way to focus on its magnitude and ignore its direction. The average sipe angle αA is shown with reference to <FIG>. The lateral sipe <NUM> can be defined as being a sipe that extends at least <NUM>% of the RTW from the tread edge limit <NUM>. This definition of the lateral sipe <NUM> can distinguish it from mico sipes which are limited in extent in the lateral direction Y and are located just at the tread edge limit <NUM>. The sipe <NUM> may be two millimeters or less in sipe thickness so as to distinguish it from a groove of the tread <NUM>. The lateral sipe <NUM>' is arranged the similar way with the exception that its extent is again measured from its proximal/associated tread edge limit <NUM>' on the right hand side rather than the left hand side tread edge limit <NUM>.

A distance d can be measured between consecutive sipes. A block aspect ratio BAR can be established as the ratio of the average sipe depth ASD with the average distance d (BAR=ASD/d). The ASD is defined along the thickness Z direction, and is independent of the inclination angle of the sipe <NUM>. In one example, all of the lateral sipes <NUM> are measured and each one has a sipe depth of <NUM> and are all spaced <NUM> apart. The average sipe depth ASD is <NUM> because all of the sipes <NUM> have this depth. The average distance d is <NUM> because all of the sipes <NUM> are spaced from consecutives ones at this distance. The block aspect ratio BAR = <NUM> / <NUM> = <NUM>. In another embodiments, there are <NUM> sipes in the tread <NUM>, and <NUM> of them have a depth of <NUM>, <NUM> of them have a depth of <NUM>, and <NUM> of them have a depth of <NUM>. The average sipe depth ASD = [(20X8mm) + (20X12mm) + (20X16mm)] / <NUM> = <NUM>. <NUM> of the sipes are <NUM> apart from a consecutive sipe, <NUM> of the sipes are <NUM> apart from a consecutive sipe, and <NUM> of the sipes are measured to be <NUM> apart from a consecutive sipe. The average distance d = [(20X25mm) + (10X35mm) + (30X40mm)] / <NUM> = <NUM>. The block aspect ratio BAR in this example is BAR= <NUM>/<NUM> = <NUM>. In some embodiments, the block aspect ratio BAR is at least <NUM>. In other embodiments, the block aspect ratio BAR is between <NUM> and <NUM>. The distance d can be a perpendicular line drawn from one average sipe line <NUM> to a consecutive average sipe line <NUM> of the adjacent sipe <NUM>. All of the distances d of the tread <NUM> can be obtained and the average can be computed to arrive at the average distance d, if the distances d are not the same for all of the sipes <NUM> in the tread <NUM>. If the depth of the sipes <NUM> are not the same, that is if one sipe <NUM> is constructed so as to have two or more depths, then <NUM> or more points across the length of the sipe <NUM> can be measured and averaged to obtain an average depth for that sipe <NUM>. In other arrangements, a weighted average depth can be used instead when the depth of the sipe <NUM> varies. The block aspect ratio BAR may be just the block aspect ratio BAR of the shoulder area <NUM>, without the measurements of the shoulder area <NUM>'. The shoulder area <NUM>' may be calculated so that it has its own block aspect ratio BAR so that the tread <NUM> has two BARs if there are sipes <NUM>, <NUM>' present in the shoulder areas <NUM>, <NUM>'.

<FIG> shows another embodiment where the sipes <NUM>, <NUM>' are undulating along their main direction when viewed on the surface of the tread <NUM>. The undulations can be zig-zagging, a single S-shape, a dog-leg shape, a square U-shaped configuration, an arc, etc. Undulated sipes <NUM>, <NUM>' promote tread stiffness due to the sipe walls interlocking when loaded on the ground. Undulations may have many different shapes and can typically be one-directional or bi-directional, and the shapes (such as the zig-zags) can be along some or all of the entire depth of the sipe <NUM>, <NUM>' in the thickness Z and longitudinal X directions. This FIG also illustrates the fact that the local sipe angle α may vary to a large extent while the average sipe angle αa is maintained between <NUM>° and <NUM>°.

<FIG> shows yet another embodiment where the sipes <NUM>, <NUM>' exit to the sides of the shoulder area <NUM>, <NUM>' at a lower angle, typically less than <NUM>°. The lateral sipes <NUM> on the left hand side of the tread <NUM> are shaped differently than the lateral sipes <NUM>' on the right hand side of the tread <NUM>. The left hand side lateral sipes <NUM> extend in the longitudinal direction X in the ISZ and then flatten out so that they no longer extend in the longitudinal direction X in the ISZ until their termination at the shoulder groove <NUM>. Several points of the lateral sipes <NUM> will be all at the maximum distance D from point A in the longitudinal direction X. However, the selection of point B which is the point that is used to measure the average sipe angle (αA) is selected as the point with maximum distance D that is closest to the tread edge limit <NUM>. As such, if there are multiple points with maximum distance D in the ISZ then the one closest to the tread edge limit <NUM> in the lateral direction Y is the one used for point B and thus the average sipe angle (αA) calculation. On the right hand side of the tread <NUM>, the lateral sipe <NUM>' extends in the rolling direction in the longitudinal direction X and then backwards against the rolling direction in the longitudinal direction X upon termination at the shoulder groove <NUM>'. The point B' in the ISZ' is that one that is farthest in the D' distance from point A' and it is but a single point.

<FIG> shows yet another embodiment where the sipes <NUM>, <NUM>' exit to the outside of the shoulder area <NUM>, <NUM>' into notches <NUM>, <NUM>' that are recessed from the tread edge limits <NUM>, <NUM>'. Tread edge notches do not affect the definition of the location of the outer boundary line OBL, OBL'. The notches <NUM>, <NUM>' can be variously shaped. An additional feature that could be present at the ends of the lateral sipes <NUM>, <NUM>' is the trumpet like end shape as disclosed in <CIT> entitled, "Tire Sipe Design for Aggression Resistance.

In <FIG>, <FIG> and <FIG>, each side of the tread <NUM> is represented as being symmetric to the other side of the tread relative to a center (or equatorial) plane of the tread <NUM>. But a tread <NUM> according to the invention may also comprise tread halves that are notably different, such as for example in <FIG>. It is also noted that the features on the left side of the tread <NUM> associated with the shoulder area <NUM> are denoted without an apostrophe, while the ones on the right hand side of the tread <NUM> with the shoulder area <NUM>' are denoted with an apostrophe.

<FIG> is an alternative exemplary embodiment of another version of the tread <NUM> in which the lateral sipes <NUM>, <NUM>' are angled in shape in the lateral direction Y such that they may be described as being in the shape of a hockey stick. The tread <NUM> is a directional tread in accordance with various exemplary embodiments.

The implementation of average sipe angles αa at the high magnitudes disclosed allows for the reduction of stresses at the trailing edge of the block bounded by the lateral sipes <NUM>, <NUM>'. This reduction of stress is due to a gradual reduction of block stiffness as the block exits contact which is a result of the tapered shape of the trailing edge of the block. This reduction of stress reduces the tendency of the block to form heel and toe wear. In addition to having this average sipe angle αa at the magnitudes disclosed, the present tread <NUM> features lateral sipes <NUM>, <NUM>' that are inclined in a "negative" direction in order to improve the irregular wear performance of the tread <NUM>.

the negative inclination of the sipe <NUM>, <NUM>' produces an orientation in which the bottom of the sipe <NUM>, <NUM>' enters the contact patch <NUM> before the top of the sipe <NUM>, <NUM>' at the outer surface <NUM>, <NUM>'. It has been discovered that if this angle is sufficiently high, for example greater than <NUM> degrees, in a shoulder area <NUM>, <NUM>' that the blocks bounded by the sipes <NUM>, <NUM>' behave more like a continuous rib. The high stresses formed at the leading and trailing edges of the block due to block compression are greatly reduced as if no sipe <NUM>, <NUM>' were present in the shoulder area <NUM>, <NUM>'. During rolling, applicant theorizes that the sipe <NUM>, <NUM>' closes up before it enters the contact patch <NUM> thus limiting the Poisson effect that develops as the block is compressed in the contact patch <NUM>. Since no Poisson effect can take place due to the gap being closed, no leading-trailing edge stress can be formed. By adding the negative inclination of the sipe <NUM>, <NUM>' to the average sipe angle αa, αa' magnitude feature the benefits of both mechanisms may be obtained to give the shoulder area <NUM>, <NUM>' improved irregular wear performance. However, too much of one, or too much of both, of these will result in a block that is too supple and subject to abnormal wear and/or aggression damage and should be avoided.

The present tread <NUM> utilizes lateral sipes <NUM>, <NUM>' in the shoulder area <NUM>, <NUM>' that include both the negative inclination of the sipe <NUM>, <NUM>' and the average sipe angle αa, αa' magnitude feature that together create a synergistic effect in reducing abnormal wear. <FIG> shows a cross-sectional view at line <NUM>-<NUM> of <FIG> in which the negative inclination angle can be shown and described. The lateral sipe <NUM> is straight in shape and has a constant cross-sectional shape and extends down into the tread <NUM>. The shoulder area <NUM> has an outer surface <NUM> into which the lateral sipe <NUM> extends downward at an angle to the thickness, radial direction Z. A sipe top point <NUM> is present at the top of the lateral sipe <NUM> at the outer surface <NUM>. The lateral sipe <NUM> extends into the tread <NUM> until it terminates at a sipe bottom <NUM> which is the location farthest from the opening at the sipe top point <NUM>. A sipe bottom point <NUM> is noted at a location at the sipe bottom <NUM>. A sipe inclination line <NUM> extends from the sipe bottom point <NUM> to the sipe top point <NUM>. The bottom of the sipe <NUM> features a tear drop, but this feature is optional in other embodiments. The tear drop can be sized so that its average diameter is greater than the width of the sipe <NUM> that is outside of its tear drop portion. The tear drop can be provided in various cross-sectional shapes, and can have a cross-sectional area that is from <NUM><NUM> to <NUM><NUM>.

A reference line <NUM> extends through the sipe bottom point <NUM> and through the outer surface <NUM>. The reference line <NUM> is oriented completely in the radial direction Z and does not have a component in the longitudinal/circumferential direction X or the lateral/axial direction Y. The radial direction Z could in some instances be described as the thickness direction Z such as when the tread <NUM> is not located on a tire. In these instances, the reference line <NUM> again only extends in the thickness direction Z and not in the longitudinal direction X or the lateral direction Y. The inclination of the lateral sipe <NUM> is observed upon comparison of the orientation of the sipe inclination line <NUM> to the reference line <NUM>. The sipe inclination line <NUM> is oriented at a sipe inclination angle <NUM> to the reference line <NUM>. The sipe inclination angle <NUM> may be from <NUM> degrees to <NUM> degrees, from <NUM> degrees to <NUM> degrees, from <NUM> degrees to <NUM> degrees, from <NUM> degrees to <NUM> degrees, from <NUM> degrees to <NUM> degrees, from <NUM> degrees to <NUM> degrees, from <NUM> degrees to <NUM> degrees, from <NUM> degrees to <NUM> degrees, from <NUM> degrees to <NUM> degrees, from <NUM> degrees to <NUM> degrees, from <NUM> degrees to <NUM> degrees, or from <NUM> degrees to <NUM> degrees in accordance with various exemplary embodiments.

The inclination of the sipe inclination line <NUM> to the reference line <NUM> is negative in direction in that it is against the rolling direction RD of the tread <NUM>. In this regard, the sipe bottom point <NUM> is configured to enter the contact patch <NUM> of the tread <NUM> as it engages the ground <NUM> before the sipe top point <NUM>. The reference line <NUM>, the sipe bottom point <NUM>, the sipe inclination line <NUM>, the sipe top point <NUM>, and the sipe inclination angle <NUM> all fall within a reference plane <NUM>. The cross-section in <FIG> likewise falls within the reference plane <NUM> so all of these elements can be viewed in relation to one another. <FIG> shows the orientation of the reference plane <NUM> relative to the rest of the tread <NUM>. As shown, the reference plane <NUM> is oriented in the longitudinal/circumferential direction X such that the longitudinal/circumferential direction X, and the rolling direction RD, lies within the reference plane <NUM>. The lateral/axial direction Y is perpendicular to the reference plane <NUM>. The sipe top point <NUM> within the reference plane <NUM> is located within the shoulder area <NUM>. In some instances the elements that lie within the reference plane <NUM> such as the sipe bottom point <NUM>, the sipe top point <NUM>, the sipe inclination line <NUM>, the reference line <NUM>, and the sipe inclination angle <NUM> are all located in the shoulder area <NUM>.

<FIG> is a view similar to that of <FIG> but with a lateral sipe <NUM> that instead of having a straight extension from the sipe bottom point <NUM> to the sipe top point <NUM> has instead an undulation between these points <NUM>, <NUM>. The sipe inclination line <NUM> is inclined at the sipe inclination angle <NUM> relative to the reference line <NUM>. The points <NUM> and <NUM>, and lines <NUM> and <NUM> and angle <NUM> are defined in the same way as previously discussed. As shown, the sipe inclination line <NUM> is not present within the lateral sipe <NUM> at certain locations due to the undulations.

Another cross-sectional view is shown in <FIG> which is a cross-section taken along line <NUM>-<NUM> of <FIG> but with the addition of the ground <NUM> into the figure and with the tread <NUM> being part of a tire. The reference plane <NUM> is again oriented relative to the rolling direction RD and the longitudinal/circumferential direction X such that they lie within the reference plane <NUM>. The inclination components of the lateral sipe <NUM> such as the sipe bottom point <NUM>, the sipe top point <NUM>, the sipe inclination line <NUM>, the reference line <NUM>, and the sipe inclination angle <NUM> are located within the shoulder area <NUM> and can be arranged as described above and a repeat of this information is not necessary. The tire is rolled in the rolling direction RD so that a portion of the tread <NUM> has entered the contact patch <NUM> upon contact with the ground <NUM>. The direction of inclination of the lateral sipe <NUM> is shown in that the sipe bottom point <NUM> enters the contact patch <NUM> first before the sipe top point <NUM>. In this regard, the lateral sipe <NUM> is said to be oriented at a "negative" sipe angle in that it is oriented away from the direction of travel of the tread <NUM> upon forward motion. If the truck were to be put into reverse, of course the opposite configuration would result in which the sipe top point <NUM> would first enter the contact patch <NUM> followed by the sipe bottom point <NUM>. Upon forward motion of the tread <NUM>, the sipe bottom point <NUM> will exit the contact patch <NUM> first before the sipe top point <NUM>.

The negative inclination angle of the lateral sipe <NUM> need not be present along the entire length of the lateral sipe <NUM> in the shoulder area <NUM>. However, at least one location between the OBL and the defined point (point B) lying <NUM>%-<NUM>% in from the tread edge limit <NUM> must include the sipe top point <NUM> such that the reference plane <NUM> has the sipe top point <NUM> within it in addition to the various other elements such as the sipe bottom point <NUM>, the sipe inclination line <NUM>, the reference line <NUM>, and the previously mentioned sipe inclination angle <NUM>. Other locations along the average sipe line <NUM> within the shoulder area <NUM> can also have the sipe top point <NUM> that is within the reference plane <NUM> which in turn includes the various elements mentioned, but not all of the locations along the average sipe line <NUM> need have a sipe top point <NUM> with a reference plane <NUM> and associated components in which the previously discussed sipe inclination angle <NUM> has the described magnitudes or direction. As such, it is not required that the entire lateral sipe <NUM> across the entire shoulder area <NUM> between points A and B have the negative inclination angle of the magnitudes discussed. However, in some embodiments, the entire lateral sipe <NUM> across the entire area from the OBL to the designated lateral sipe <NUM> position in the ISZ does in fact have a negative inclination angle having the sipe inclination angle <NUM> magnitudes mentioned and in the proper negative orientation.

In some instances, the sipe inclination angle <NUM> is not the same along the entire length between points A and B. <FIG> shows a portion of the tread <NUM> in which the lateral sipe <NUM> extends into the tread <NUM> from the outer surface at different angular orientations so that a constant sipe inclination angle <NUM> is not present across the entire lateral sipe <NUM> in the shoulder area <NUM> between points A and B. As shown, on the left hand side of <FIG> sipe top and bottom points <NUM>, <NUM> are noted with counterpart reference plane <NUM> and sipe inclination line <NUM>. The sipe inclination angle <NUM> can be calculated at this location as previously discussed. The shoulder area <NUM> between points A and B has additional points <NUM>, <NUM> linked with another reference plane <NUM> and sipe inclination line <NUM>. The sipe inclination angle <NUM> is different at this location than at the location on the left hand side. Still further, the lateral sipe <NUM> changes at the right hand side such that the right hand location points <NUM>, <NUM> with associated plane <NUM> and sipe line <NUM> has yet a different sipe inclination angle <NUM>. In instances where the sipe inclination angle <NUM> is not constant in the shoulder portion <NUM> between points A and B, the sipe inclination angle <NUM> of the lateral sipe <NUM> is determined by obtaining an average of the sipe inclination angle <NUM> at five equally spaced points along the lateral sipe <NUM>. As an example, the sipe inclination angle <NUM> can be measured at five different equally spaced locations along its length between points A and B to yield values of <NUM> degrees, <NUM> degrees, <NUM> degrees, <NUM> degrees, and <NUM> degrees for sipe inclination angle <NUM> of <NUM> degrees ((<NUM>+<NUM>+<NUM>+<NUM>+<NUM>) / <NUM> = <NUM>).

Any number of the lateral sipes <NUM> as described can be present in the tread <NUM>. In some instances, all of the lateral sipes <NUM> of the shoulder area <NUM> are as described. In other embodiments, only one of the lateral sipes <NUM> in the shoulder area <NUM> is as described. Additionally or alternatively, the lateral sipes <NUM> need not only be in the shoulder area <NUM> on the left hand side of the FIGs, but could additionally or alternatively be located on the shoulder area <NUM>' located on the right hand side of the FIGs. A portion of a shoulder area <NUM>' located on the right hand side of the tread <NUM> is shown in <FIG> in perspective view. The outer surface <NUM>' has a lateral sipe <NUM>' with an average sipe angle αa' as previously discussed. Further, the lateral sipe <NUM>' is inclined in the negative direction to the magnitude extents as previously mentioned. A sipe bottom point <NUM>' is at the sipe bottom <NUM>' in the same plane as the reference plane <NUM>' which is the same plane the rolling direction RD and the longitudinal/circumferential direction X are located. A sipe inclination line <NUM>' runs from the sipe bottom point <NUM>' to the sipe top point <NUM>' and lies within the reference plane <NUM>', as does a reference line <NUM>' that extends through the sipe bottom point <NUM>' and has a component of extension only in the thickness direction / radial direction Z. The sipe inclination angle <NUM>' denotes the orientation of the sipe inclination line <NUM>' relative to the reference line <NUM>'. The sipe inclination angle <NUM>' may be the same magnitudes as that previously discussed with respect to the sipe inclination angle <NUM> above. Also, the lateral sipe <NUM>' is inclined in the negative direction with respect to the rolling direction RD as previously mentioned. Any number of the lateral sipes <NUM>' on the right hand side of the tread <NUM> in the shoulder area <NUM>' can be configured in this manner such as one, two, or all of them.

The measurements may be taken at the outer surfaces <NUM>, <NUM>' of a new tire <NUM>, unless expressly noted, such as those pertaining to the depth of the sipes <NUM>, <NUM>', the sipe bottom points <NUM>, <NUM>', the reference planes <NUM>, <NUM>' and other positions of the tread <NUM>. In some instances, the measurements can be taken after the tread <NUM> has undergone some amount of wear.

Claim 1:
A heavy truck tire tread (<NUM>) having a longitudinal direction (X), a lateral direction (Y) and a thickness direction (Z), said tread comprising:
- a tread edge limit (<NUM>);
- a shoulder area (<NUM>) extending in the lateral direction (Y) from the tread edge limit (<NUM>);
wherein the shoulder area (<NUM>) has an outer surface (<NUM>) and a lateral sipe (<NUM>) with an average sipe line (<NUM>) at the outer surface (<NUM>) oriented at an average sipe angle (αa) between a point A where the lateral sipe (<NUM>) intersects an outer boundary line (OBL) and a point B that is where the lateral sipe (<NUM>) is farthest from point A in the longitudinal direction (X) from <NUM>% to <NUM>% of a rolling tread width (RTW) from the tread edge limit (<NUM>) in the lateral direction (Y), wherein the outer boundary line (OBL)is a longitudinal straight line running at a distance of <NUM> from the tread edge limit,
characterised in that
the average sipe angle (αa) is greater than <NUM>° in absolute value, wherein the average sipe angle (αa) is oriented at an angle relative to the lateral direction (Y) running inboard to outboard in the lateral direction (Y), wherein the lateral sipe (<NUM>) extends from the tread edge limit (<NUM>) in the lateral direction (Y) past the outer boundary line (OBL) and to the shoulder groove (<NUM>) where the lateral sipe (<NUM>) terminates;
the lateral sipe (<NUM>) has a sipe bottom (<NUM>), wherein the longitudinal direction (X) lies in a reference plane (<NUM>), wherein a sipe bottom point (<NUM>) is located in the reference plane (<NUM>) at the sipe bottom (<NUM>), wherein a sipe top point (<NUM>) is located in the reference plane (<NUM>) at the average sipe line (<NUM>), wherein a sipe inclination line (<NUM>) extends from the sipe bottom point (<NUM>) to the sipe top point (<NUM>), wherein a reference line (<NUM>) extends in the thickness direction (Z) through the sipe bottom point (<NUM>) wherein the reference line (<NUM>) does not have a component in the longitudinal direction (X) or the lateral direction (Y), wherein the sipe inclination line (<NUM>) is at a sipe inclination angle (<NUM>) to the reference line (<NUM>), wherein the sipe inclination angle (<NUM>) is from <NUM> to <NUM> degrees, wherein the sipe bottom point (<NUM>) is configured to approach a contact patch (<NUM>) before the sipe top point (<NUM>) upon forward motion.