Patent Description:
Tires of different tread patterns and construction are known in the art. Both symmetric and asymmetric tread patterns may be configured to optimize certain features, such as braking performance, wet handling, dry handling, snow handling, traction, wear, noise reduction, and rolling resistance. The position and orientation of carcass plies and other elements may also be configured to optimize such features. Tires can be categorized into symmetric tires, asymmetric tires and directional tires. Symmetric tires have no preferred mounting method while asymmetric tires have a preferred outboard face and directional tires have a preferred rolling direction.

Many vehicles have different performance needs for tires on a front axle versus tires on a rear axle. The front axle may support a greater portion of the weight of the vehicle. In some instances, the front axle may support <NUM>% of the weight of the vehicle. Additionally, in front wheel drive tires, the rear tires only contribute to braking, and contribute no driving force. Similarly, in rear wheel drive tires, the front tires contribute only to braking and contribute no driving force.

Additionally, the radial and lateral forces may be distributed differently in the front and rear tires. Further, the camber of front tires may be different from that of rear tires in some vehicles. This causes different parts of a tread pattern to engage a rolling surface on a front tire versus a rear tire.

<FIG> is a sample histogram illustrating the distribution of fore/aft forces on front and rear tires of exemplary rear wheel drive vehicles driven on a simulated road course. The histogram is not meant to illustrate properties of a specific tire or specific car, but is presented here to illustrate some of the different forces exerted on front tires versus rear tires.

The illustrated example shows forces on two different cars. The x-axis represents a ratio of the fore-aft force to the static front load of a tire. The negative numbers on the axis represent a braking force and the positive numbers represent a driving force. The y-axis represents the percentage of each occurrence.

As can be seen from <FIG>, rear wheel drive vehicles often exert small braking forces on the front tires, and may occasionally exert larger braking forces on the front tires. However, as one would expect, rear wheel drive tires do not any exert driving force on the front tires.

By contrast, <FIG> illustrates that rear wheel drive vehicles often exert small driving forces on the rear tires, and occasionally exert larger driving forces on the rear tires. Rear wheel drive vehicles may also exert small to medium braking forces on the rear tires. Although the histogram of <FIG> is specific to a given simulated road course, it should be understood that while changes to the road course would affect the histogram, the general differences between front and rear tires would still hold.

While "directional tires" are known in the art, it was not generally known how such tires would perform in both a clockwise and counterclockwise direction. Therefore, a sample of existing directional tires were tested on a flat belt tire test machine, which closely controls and sweeps through a matrix of slip rates and loads while recording reaction forces and moments at the tire/wheel assembly center. Table <NUM> shows the Peak Fx metric relating to dry traction calculated from the resulting data.

In Table <NUM>, Peak Fx is the greatest longitudinal force on the slip ratio versus a longitudinal force (N) curve. Peak Fx is known by those skilled in the arts to correlate with traction performance.

As can be seen in Table <NUM>, although the directional tires are configured to be rotated in a specific direction, the differences in peak Fx due to changing the rolling direction were never greater than <NUM>%. Some of the <NUM>% difference is likely due to the error in the testing/measurement, because even the Non Directional Tire A showed differences. Accordingly, current directional tires do not display a significant difference in dry driving or braking traction to affect a significant change in on vehicle performance based on tire rolling direction.

A tire according to the preamble of claim <NUM> is known from <CIT>. Similar tires are also known from <CIT> and <CIT>.

In addition, <CIT> proposes to provide a tire with a rotational tread so as to equip different axles of a vehicle with the same tire in a respective opposite directions.

<CIT>, which merely constitutes prior art under Art. <NUM>(<NUM>) EPC, discloses an arrangement of pneumatic tires of a vehicle, in which an inclination angle of tread segments of the tires mounted to a front axle of the vehicle is opposite to the inclination angle of the tires mounted to the rear axle.

According to the invention, a tire as defined in claim <NUM> and a method of mounting a plurality of tires on a vehicle as defined in claim <NUM> are provided. The dependent claims define preferred and/or advantageous embodiments of the invention.

In the accompanying drawings like elements are identified with the same reference numerals.

The definitions include various examples or forms of components that fall within the scope of a term and that may be used for implementation.

"Axial" or "axially" refer to a direction that is parallel to the axis of rotation of a tire.

"Bead" refers to the part of the tire that contacts the wheel and defines a boundary of the sidewall.

"Carcass ply" refers to a structural member that connects the bead to a tread, and may be continuous or discrete.

"Circumferential" and "circumferentially" refer to a direction extending along the perimeter of the surface of the tread perpendicular to the axial direction.

"Equatorial plane" refers to the plane that is perpendicular to the tire's axis of rotation and passes through the center of the tire.

"Radial" and "radially" refer to a direction perpendicular to the axis of rotation of a tire.

"Sidewall" refers to that portion of the tire between the tread and the bead.

"Tread" refers to that portion of the tire that comes into contact with the road under normal inflation and load.

Directions are stated in this disclosure with reference to a top view of a vehicle, with respect to a longitudinal axis of the vehicle. The terms "inward" and "inwardly" refer to a general direction towards the longitudinal axis of the vehicle, whereas "outward" and "outwardly" refer to a general direction away from the longitudinal axis of the vehicle. Thus, when relative directional terms such as "inner" and "outer" are used in connection with an element, the "inner" element is spaced closer to the longitudinal axis of the vehicle than the "outer" element. Similarly, the terms "left" and "right" are stated in reference to a top view of the vehicle on which tires are mounted, with respect to a longitudinal axis of the vehicle. The terms "front" and "rear" are also stated in reference to a vehicle on which tires are mounted.

<FIG> show a perspective view and side view, respectively, of a schematic drawing of one embodiment of a tire <NUM> having an axle specific rolling direction. <FIG> shows a multi-perspective view of the tire <NUM> in a first orientation 110a and a second orientation 110b. The tire <NUM> is described in reference to all of these figures.

The tire <NUM> includes a first and second bead portion (not shown), a first sidewall 120a, and a second sidewall 120b. The tire <NUM> has two rotation directions. When the tire is viewed from the second sidewall 120b (as shown in <FIG>), the first rotation direction of the tire <NUM> is in the clockwise direction and the second rotation direction of the tire <NUM> is in the counterclockwise direction.

The tire <NUM> further includes at least one carcass ply (not shown) extending from the first bead portion to the second bead portion, a circumferential belt disposed above the carcass ply (not shown), and a circumferential tread <NUM> disposed above the belt. The circumferential tread <NUM> has a tread pattern shown schematically at <NUM>. In one embodiment, the tread pattern <NUM> has discrete rotational asymmetry of the second order, which causes the tire <NUM> to be directional. Therefore, when the tire <NUM> is in the first orientation 110a, the tread pattern <NUM> has a first appearance, and when the tire <NUM> is placed in the second orientation 110b, the reversed tread pattern <NUM> has a second appearance different from the first appearance.

The asymmetry of the tread pattern may cause the tread to exhibit different properties when the tire <NUM> is rotated in the first direction versus the second direction. The tread pattern and the position and orientation of the carcass ply may be selected such that desirable properties for a front tire are exhibited when the tire <NUM> is rotated in the first direction, and desirable properties for a rear tire are exhibited when the tire <NUM> is rotated in the second direction.

For example, the tread pattern may be selected such that when the tire is rotated in the first rotation direction, the circumferential tread exhibits a first braking performance and a first driving traction performance, and when the tire is rotated in the second direction, the circumferential tread exhibits a second braking performance that is lower than the first braking performance and a second driving traction performance that is higher than the first driving traction performance. In rear wheel drive vehicles, it may be more advantageous for the rear tires to exhibit higher driving traction performance. In front wheel drive vehicles, it may be more advantageous for the front tires to exhibit higher driving traction performance.

In another example, the tread pattern may be selected such that the circumferential tread exhibits a first wear performance when rotated in the first direction, and a second wear performance different from the first wear performance when rotated in the second direction. For example, in front wheel drive vehicles, front tires tend to wear faster. In rear wheel drive tires, rear tires tend to wear faster. The tread pattern may be selected to reduce the discrepancy between the wear rates of front and rear tires.

In yet another example, the tread pattern may be selected such that the circumferential tread exhibits a first snow traction performance when rotated in the first direction, and a second snow traction performance that is different from the first snow traction performance when rotated in the second direction. The tread pattern may also be selected such that other properties are affected by a change in rotation direction.

Additionally, or in the alternative, the position and orientation of the carcass ply may be selected such that the carcass ply causes the tire to exhibit different properties according to the rotation direction. Such differences in carcass plies may not be readily observable from the exterior of the tire, but the tire would still exhibit asymmetric properties.

In one embodiment, the first rotation direction may be indicated as a Front Rotation Direction, and the second rotation direction may be indicated as a Rear Rotation Direction on one or more locations on the tire. As can be seen in the illustrated embodiment, a first indicia 150a is disposed on the first sidewall 120a and a second indicia 150b is disposed on the second sidewall 120b of the tire <NUM>. Both the first indicia 150a and the second indicia 150b include an indicator designating the first rotation direction as a front tire rotation direction and the second rotation direction as a rear tire rotation direction. While the illustrated embodiment shows arrows with a written description, it should be understood that the indicia may take any form or size.

Such indicia may be used to aid a person in mounting axle specific tires on a vehicle. As shown in <FIG>, the properties of the tire <NUM> may be selected so that four tires having substantially the same sidewalls, carcass plies, and circumferential tread may be mounted on a vehicle <NUM> in such a way that first and second tires <NUM><NUM>, <NUM><NUM> on a front axle <NUM> exhibit different properties than third and fourth tires <NUM><NUM>, <NUM><NUM> mounted on a rear axle <NUM>.

In the illustrated embodiment, the first tire <NUM><NUM> is mounted on a first wheel (not shown), the second tire <NUM><NUM> is mounted on a second wheel (not shown), the third tire <NUM><NUM> is mounted on a third wheel (not shown), and the fourth tire <NUM><NUM> is mounted on a fourth wheel (not shown). The first wheel and tire are mounted on a left end of the front axle <NUM> of a vehicle <NUM>, such that a first sidewall 120a<NUM> of the first tire <NUM><NUM> faces outwards, (i.e., away from a longitudinal axis A of the vehicle <NUM>), and a second sidewall 120b<NUM> of the first tire <NUM><NUM> faces inwards (i.e., towards the longitudinal axis A of the vehicle <NUM>). The second wheel and tire are mounted on a right end of the front axle <NUM> of the vehicle <NUM>, such that a first sidewall 120a<NUM> of the second tire <NUM><NUM> faces inwards, and a second sidewall 120b<NUM> of the second tire <NUM><NUM> faces outwards. The third wheel and tire are mounted on a left end of the rear axle <NUM> of the vehicle <NUM>, such that a first sidewall 120as of the third tire <NUM><NUM> faces inwards, and a second sidewall 120b<NUM> of the third tire <NUM><NUM> faces outwards. The fourth wheel and tire are mounted on a right end of the rear axle <NUM> of the vehicle <NUM>, such that a first sidewall 120a<NUM> of the fourth tire <NUM><NUM> faces outwards, and a second sidewall 120b<NUM> of the fourth tire <NUM><NUM> faces inwards.

It should be understood that the tires may be mounted on the vehicle in any order, and that certain steps described above may be performed concurrently or in a different order.

When servicing the vehicle, the tires may be rotated in the manner illustrated in <FIG>, without having to dismount the tires from the wheels. The first wheel and tire are removed from the front axle <NUM> of the vehicle <NUM> and the fourth wheel and tire are removed from the rear axle <NUM> of the vehicle <NUM>. The first wheel and tire are mounted on the right end of the rear axle <NUM> of the vehicle <NUM>, such that the first sidewall 120a<NUM> of the first tire <NUM><NUM> faces outwards, and the second sidewall 120b<NUM> of the first tire <NUM><NUM> faces inwards. The fourth wheel and tire are mounted on the left end of the front axle <NUM> of the vehicle <NUM>, such that a first sidewall 120a<NUM> of the fourth tire <NUM><NUM> faces outwards, and a second sidewall 120b<NUM> of the fourth tire <NUM><NUM> faces inwards.

The second wheel and tire are removed from the front axle <NUM> of the vehicle <NUM> and the third wheel and tire are removed from the rear axle <NUM> of the vehicle <NUM>. The second wheel and tire are mounted on the left end of the rear axle <NUM> of the vehicle <NUM>, such that a first sidewall 120a<NUM> of the second tire <NUM><NUM> faces inwards, and a second sidewall 120b<NUM> of the second tire <NUM><NUM> faces outwards. The third wheel and tire are mounted on the right end of the front axle <NUM> of the vehicle <NUM>, such that a first sidewall 120a<NUM> of the third tire <NUM><NUM> faces inwards, and a second sidewall 120b<NUM> of the third tire <NUM><NUM> faces outwards.

It should be understood that the steps of rotating tires may be performed in any order and that certain steps described above may be performed concurrently or in a different order. Additionally, it should also be understood that the tires may be dismounted from the wheels such that they may be remounted in any position.

While <FIG> illustrate bidirectional tires that exhibit desirable front tire characteristics when rotated in a first direction, and desirable rear tire characteristics when rotated in a second direction, bidirectional tires may also be designed to exhibit desirable summer performance characteristics when rotated in a first direction, and desirable winter performance characteristics when rotated in a second direction. <FIG> show a perspective view and side view, respectively, of a schematic drawing of one embodiment of a tire <NUM> having a season specific rolling direction. <FIG> shows a multi-perspective view of the tire <NUM> in a first orientation 310a and a second orientation 310b. The tire <NUM> is described in reference to all of these figures.

The tire <NUM> includes a first and second bead portion (not shown), a first sidewall 320a, and a second sidewall 320b. The tire <NUM> has two rotation directions. When the tire is viewed from the second sidewall 320b (as shown in <FIG>), the first rotation direction of the tire <NUM> is in the clockwise direction and the second rotation direction of the tire <NUM> is in the counterclockwise direction.

The tire <NUM> further includes at least one carcass ply (not shown) extending from the first bead portion to the second bead portion, a circumferential belt disposed above the carcass ply (not shown), and a circumferential tread <NUM> disposed above the belt. The circumferential tread <NUM> has a tread pattern shown schematically at <NUM>. In one embodiment, the tread pattern <NUM> has discrete rotational asymmetry of the second order, which causes the tire <NUM> to be directional. Therefore, when the tire <NUM> is in the first orientation 310a, the tread pattern <NUM> has a first appearance, and when the tire <NUM> is placed in the second orientation 310b, the reversed tread pattern <NUM> has a second appearance different from the first appearance.

The asymmetry of the tread pattern may cause the tread to exhibit different properties when the tire <NUM> is rotated in the first direction versus the second direction. The tread pattern and the position and orientation of the carcass ply may be selected such that desirable properties for summer performance are exhibited when the tire <NUM> is rotated in the first direction, and desirable properties for winter performance are exhibited when the tire <NUM> is rotated in the second direction.

For example, the tread pattern may be selected such that the circumferential tread exhibits a first snow traction performance when rotated in the first direction, and a second snow traction performance that is different from the first snow traction performance when rotated in the second direction. The tread pattern may also be selected such that other properties are affected by a change in rotation direction.

In another example, the tread pattern may be selected such that when the tire is rotated in the first rotation direction, the circumferential tread exhibits a first stopping distance performance, and when the tire is rotated in the second direction, the circumferential tread exhibits a second stopping distance performance that is lower than the first stopping performance. Stopping distance performance may be more important in summer, when vehicles tend to be driven at higher speeds.

In yet another example, the tread pattern may be selected such that the circumferential tread exhibits a first wear performance when rotated in the first direction, and a second wear performance different from the first wear performance when rotated in the second direction. For example, tires tend to wear slower in the winter when they are driven over snow. The tread pattern may be selected to reduce the discrepancy between the wear rates in summer and winter.

In still another example, the tread pattern may be selected such that the circumferential tread exhibits a first noise performance when rotated in the first direction, and a second noise performance different from the first noise performance when rotated in the second direction. For example, tires tend to be quieter in the winter when they are driven over snow. The tread pattern may be selected to reduce the discrepancy between the tire noise in summer and winter.

In one embodiment, the first rotation direction may be indicated as a Summer Rotation Direction, and the second rotation direction may be indicated as a Winter Rotation Direction on one or more locations on the tire. As can be seen in the illustrated embodiment, a first indicia 350a is disposed on the first sidewall 320a and a second indicia 350b is disposed on the second sidewall 320b of the tire <NUM>. Both the first indicia 350a and the second indicia 350b include an indicator designating the first rotation direction as a summer rotation direction and the second rotation direction as a winter rotation direction. While the illustrated embodiment shows arrows with a written description, it should be understood that the indicia may take any form or size.

Such indicia may be used to aid a person in mounting season specific tires on a vehicle. As shown in <FIG>, the properties of the tire <NUM> may be selected so that four tires having substantially the same sidewalls, carcass plies, and circumferential tread may be mounted on a vehicle <NUM> in such a way that all tires <NUM><NUM>, <NUM><NUM>,<NUM><NUM>, <NUM><NUM> exhibit desirable summer performance characteristics.

In the illustrated embodiment, the first tire <NUM><NUM> is mounted on a first wheel (not shown), the second tire <NUM><NUM> is mounted on a second wheel (not shown), the third tire <NUM><NUM> is mounted on a third wheel (not shown), and the fourth tire <NUM><NUM> is mounted on a fourth wheel (not shown). The first wheel and tire are mounted on a left end of the front axle <NUM> of a vehicle <NUM>, such that a first sidewall 320a<NUM> of the first tire <NUM><NUM> faces outwards, (i.e., away from a longitudinal axis A of the vehicle <NUM>), and a second sidewall 320b<NUM> of the first tire <NUM><NUM> faces inwards (i.e., towards the longitudinal axis A of the vehicle <NUM>). The second wheel and tire are mounted on a right end of the front axle <NUM> of the vehicle <NUM>, such that a first sidewall 320a<NUM> of the second tire <NUM><NUM> faces inwards, and a second sidewall 320b<NUM> of the second tire <NUM><NUM> faces outwards. The third wheel and tire are mounted on a left end of the rear axle <NUM> of the vehicle <NUM>, such that a first sidewall 320as of the third tire <NUM><NUM> faces outwards, and a second sidewall 320b<NUM> of the third tire <NUM><NUM> faces inwards. The fourth wheel and tire are mounted on a right end of the rear axle <NUM> of the vehicle <NUM>, such that a first sidewall 320a<NUM> of the fourth tire <NUM><NUM> faces inwards, and a second sidewall 320b<NUM> of the fourth tire <NUM><NUM> faces outwards.

To change direction of the tires when the season changes, the tires may be rotated in the manner illustrated in <FIG>, without having to dismount the tires from the wheels. The first wheel and tire are removed from the front axle <NUM> of the vehicle <NUM> and the fourth wheel and tire are removed from the rear axle <NUM> of the vehicle <NUM>. The first wheel and tire are mounted on the right end of the rear axle <NUM> of the vehicle <NUM>, such that the first sidewall 320a<NUM> of the first tire <NUM><NUM> faces outwards, and the second sidewall 320b<NUM> of the first tire <NUM><NUM> faces inwards. The fourth wheel and tire are mounted on the left end of the front axle <NUM> of the vehicle <NUM>, such that a first sidewall 320a<NUM> of the fourth tire <NUM><NUM> faces inwards, and a second sidewall 320b<NUM> of the fourth tire <NUM><NUM> faces outwards.

The second wheel and tire are removed from the front axle <NUM> of the vehicle <NUM> and the third wheel and tire are removed from the rear axle <NUM> of the vehicle <NUM>. The second wheel and tire are mounted on the left end of the rear axle <NUM> of the vehicle <NUM>, such that a first sidewall 320a<NUM> of the second tire <NUM><NUM> faces inwards, and a second sidewall 320b<NUM> of the second tire <NUM><NUM> faces outwards. The third wheel and tire are mounted on the right end of the front axle <NUM> of the vehicle <NUM>, such that a first sidewall 320as of the third tire <NUM><NUM> faces outwards, and a second sidewall 320b<NUM> of the third tire <NUM><NUM> faces inwards.

<FIG> shows a multi-perspective view of another embodiment of a tire <NUM> in a first orientation 510a and a second orientation 510b. The tire <NUM> includes a first and second bead portion (not shown), a first sidewall 520a, and a second sidewall 520b. The first and second sidewall 520a,b define a first mounting position and a second mounting position of the tire, in that the first sidewall 520a faces outwards in the first mounting position, and the second sidewall faces 520b faces outwards in the second mounting position.

The tire <NUM> further includes at least one carcass ply (not shown) extending from the first bead portion to the second bead portion, a circumferential belt disposed above the carcass ply (not shown), and a circumferential tread <NUM> disposed above the belt. The circumferential tread <NUM> has a tread pattern shown schematically at <NUM>. The tread pattern <NUM> is asymmetric about the equatorial plane of the tire <NUM>. Therefore, when the tire <NUM> is in the first orientation shown in <FIG>, the tread pattern <NUM> has a first appearance, and when the tire <NUM> is rotated to the second orientation shown in <FIG>, the reversed tread pattern <NUM> has a second appearance different from the first appearance.

The asymmetry of the tread pattern may cause the tread to exhibit different properties when the tire <NUM> is mounted in the first mounting position versus the second mounting position. For example, the tread pattern may be selected to account for first wear characteristics when a tire is mounted in the first position, and to account for second wear characteristics different from the first wear characteristics when the tire is mounted in the second position. As one of ordinary skill in the art would understand, the front and rear tires may have different cambers. Additionally, the weight of the vehicle may be distributed different on the front and rear axles. These differences may cause the front tires to have different footprints from the rear tires. The tread patterns in the first and second mounting positions of the tires may be selected to account for these different footprints.

In another example, the tread pattern may be selected such that the circumferential tread exhibits a first snow traction performance when mounted in the first position, and a second snow traction performance different from the first snow traction performance when mounted in the second position.

The tread pattern may also be selected such that other properties are affected by a change in mounting position. For example, the front and rear tires of a vehicle may experience different lateral forces. The tread pattern may be selected to effectively manage these different lateral forces.

Additionally, or in the alternative, the position and orientation of the carcass ply may be selected such that the carcass ply causes the tire to exhibit different properties according to the mounting position. Such differences in carcass plies may not be readily observable from the exterior of the tire, but the tire would still exhibit asymmetric properties.

The tread pattern and the position and orientation of the carcass ply may be designed to account for the different forces that are exhibited on the front and rear tires. Such different forces may cause the front and rear tires to wear differently.

In such an embodiment, the first mounting direction may be indicated as a Front Mounting Position, and the second rotation direction may be indicated as a Rear Mounting Position on one or more locations on the tire. As can be seen in the illustrated embodiment, a first indicia 550a is disposed on the first sidewall 520a and a second indicia 550b is disposed on the second sidewall 520b of the tire <NUM>. While the illustrated embodiment shows indicia that includes a written description, it should be understood that the indicia may take any form or size.

In the illustrated embodiment, the first tire <NUM><NUM> is mounted on a first wheel (not shown), the second tire <NUM><NUM> is mounted on a second wheel (not shown), the third tire <NUM><NUM> is mounted on a third wheel (not shown), and the fourth tire <NUM><NUM> is mounted on a fourth wheel (not shown). The first wheel and tire are mounted on a left end of the front axle <NUM> of a vehicle <NUM>, such that a first sidewall 520a<NUM> of the first tire <NUM><NUM> faces outwards, and a second sidewall 520b<NUM> of the first tire <NUM><NUM> faces inwards. The second wheel and tire are mounted on a right end of the front axle <NUM> of the vehicle <NUM>, such that a first sidewall 520a<NUM> of the second tire <NUM><NUM> faces outwards, and a second sidewall 520b<NUM> of the second tire <NUM><NUM> faces inwards. The third wheel and tire are mounted on a left end of the rear axle <NUM> of the vehicle <NUM>, such that a first sidewall 520as of the third tire <NUM><NUM> faces inwards, and a second sidewall 520bs of the third tire <NUM><NUM> faces outwards. The fourth wheel and tire are mounted on a right end of the rear axle <NUM> of the vehicle <NUM>, such that a first sidewall 520a<NUM> of the fourth tire <NUM><NUM> faces inwards, and a second sidewall 520b<NUM> of the fourth tire <NUM><NUM> faces outwards.

When servicing the vehicle, the tires may be rotated in the manner illustrated in <FIG>, without having to dismount the tires from the wheels. The first wheel and tire, and second wheel and tire are removed from the front axle <NUM> of the vehicle <NUM>. The first wheel and tire are mounted on the right end of the front axle <NUM> of the vehicle <NUM>, such that the first sidewall 520a<NUM> of the first tire <NUM><NUM> faces outwards, and the second sidewall 520b<NUM> of the first tire <NUM><NUM> faces inwards. The second wheel and tire are mounted on the left end of the front axle <NUM> of the vehicle <NUM>, such that a first sidewall 520a<NUM> of the second tire <NUM><NUM> faces outwards, and a second sidewall 520b<NUM> of the second tire <NUM><NUM> faces inwards.

The third wheel and tire, and fourth wheel and tire are removed from the rear axle <NUM> of the vehicle <NUM>. The third wheel and tire are mounted on the right end of the rear axle <NUM> of the vehicle <NUM>, such that a first sidewall 520a<NUM> of the third tire <NUM><NUM> faces inwards, and a second sidewall 520b<NUM> of the third tire <NUM><NUM> faces outwards. The fourth wheel and tire are mounted on the left end of the rear axle <NUM> of the vehicle <NUM>, such that a first sidewall 520a<NUM> of the fourth tire <NUM><NUM> faces inwards, and a second sidewall 520b<NUM> of the fourth tire <NUM><NUM> faces outwards.

In each of the embodiments described above, and illustrated in <FIG>, directional tread elements may be selected for the tire that display first characteristics when rotated in a first direction, and second characteristics different from the first characteristics when rotated in a second direction opposite the first direction. <FIG> illustrate examples of tread elements that exhibit different characteristics in different rolling directions. While each of these figures illustrate a single feature, it should be understood that tread elements may employ two or more of the illustrated features. For the sake of brevity the various combinations of features are not shown herein.

<FIG> is a profile view of a tread element <NUM> that does not form part of the invention but is useful for understanding the invention and exhibits first characteristics in a first rolling direction D<NUM> and second characteristics in a second rolling direction D<NUM>. The tread element <NUM> includes a first wall <NUM> and a second wall <NUM>. The first wall <NUM> is disposed at a first angle α<NUM> with respect to the base <NUM> of a groove in the tire. The second wall <NUM> is disposed at a second angle α<NUM> with respect to the base <NUM> of a groove in the tire that is greater than the first angle α<NUM>. When the tire is rotated in the first direction D<NUM>, the top of the tread element <NUM> and the first wall <NUM> form a leading edge (i.e., the edge that first comes into contact with the rolling surface). When the tire is rotated in the second direction D<NUM>, the top of the tread element <NUM> and the second wall <NUM> form a leading edge. The shallower angle α<NUM> of the first wall <NUM> causes lower edge pressure on the tread element <NUM> when the tire is rotated in the first direction D<NUM>, compared to when the tire is rotated in the second direction D<NUM>. This effect is utilized to achieve directional performance of the lug related to traction, wear, noise and other tire performance characteristics.

<FIG> is a profile view of an embodiment of a tread element <NUM> that does not form part of the invention but is useful for understanding the invention and that exhibits first characteristics in a first rolling direction D<NUM> and second characteristics in a second rolling direction D<NUM>. The tread element <NUM> includes a first wall <NUM> and a second wall <NUM>. The tread element <NUM> includes a plurality of sipes <NUM> adjacent the second wall, and no sipes adjacent the first wall. In an alternative embodiment (not shown), the tread element may have sipes adjacent both wall, but a greater number of sipes adjacent the second wall.

When the tire is rotated in the first direction D<NUM>, the top of the tread element <NUM> and the first wall <NUM> form a leading edge. When the tire is rotated in the second direction D<NUM>, the top of the tread element <NUM> and the second wall <NUM> form a leading edge, and the sipes <NUM> provide additional edges adjacent the leading edge. This effect is utilized to achieve directional performance of the lug related to traction, wear, noise and other tire performance characteristics.

<FIG> is a profile view of another embodiment of a tread element <NUM> that exhibits first characteristics in a first rolling direction D<NUM> and second characteristics in a second rolling direction D<NUM>. The tread element <NUM> includes a first wall <NUM> and a second wall <NUM>. The tread element <NUM> includes a plurality of angled sipes <NUM>. When the tire is rotated in the first direction D<NUM>, the rolling surface provides a shear force on the top of the tread element <NUM> that causes the angled sipes <NUM> to open and provide additional edges. When the tire is rotated in the second direction D<NUM>, the rolling surface provides a shear force on the top of the tread element <NUM> that causes the angled sipes <NUM> to close, thereby eliminating the additional edges. This effect is utilized to achieve directional performance of the lug related to traction, wear, noise and other tire performance characteristics.

<FIG> is a profile view of still another embodiment of a tread element <NUM> that does not form part of the invention but is useful for understanding the invention and that exhibits first characteristics in a first rolling direction D<NUM> and second characteristics in a second rolling direction D<NUM>. The tread element <NUM> includes a first wall <NUM> and a second wall <NUM>. The tread element <NUM> includes a plurality of ratchet-shaped sipes <NUM>, that may be referred to as three-dimensional (or 3D) sipes <NUM>. When the tire is rotated in the first direction D<NUM>, the rolling surface provides a shear force on the top of the tread element <NUM> that causes the ratchet-shaped sipes <NUM> to open and provide additional edges. When the tire is rotated in the second direction D<NUM>, the rolling surface provides a shear force on the top of the tread element <NUM> that causes the ratchet-shaped sipes <NUM> to close, thereby eliminating the additional edges. This effect is utilized to achieve directional performance of the lug related to traction, wear, noise and other tire performance characteristics.

<FIG> is a profile view of a tread element <NUM> that does not form part of the invention but is useful for understanding the invention and exhibits first characteristics in a first rolling direction D<NUM> and second characteristics in a second rolling direction D<NUM>. The tread element <NUM> includes a first wall <NUM> and a second wall <NUM>. The tread element <NUM> includes an edge treatment. In this embodiment, the edge treatment is a rounded chamfer <NUM> extending from the second wall <NUM> to a top surface of the tread element <NUM>. When the tire is rotated in the first direction D<NUM>, the top of the tread element <NUM> and the first wall <NUM> form a leading edge. When the tire is rotated in the second direction D<NUM>, the top of the tread element <NUM> and the second wall <NUM> form a leading edge. The rounded chamfer <NUM> extending from the second wall <NUM> causes lower edge pressure on the tread element <NUM> when the tire is rotated in the second direction D<NUM>, compared to when the tire is rotated in the first direction D<NUM>. It should be understood that other edge treatments may also be employed, such as planar chamfers.

It should be understood that the tread element <NUM> may be a lug, bounded by a pair of grooves. Alternatively, the tread element <NUM> may represent a portion of a lug, bounded by a pair of sipes.

In the illustrated embodiment, the rounded chamfer <NUM> has a length that is substantially greater than its height. In one particular embodiment, the length is four times greater than the height. In another known embodiment, the length is two times greater than the height. In an alternative embodiment (not shown), the height is greater than or equal to the length.

<FIG> is a profile view of still another embodiment of a tread element <NUM> that exhibits first characteristics in a first rolling direction D<NUM> and second characteristics in a second rolling direction D<NUM>. The tread element <NUM> shows that multiple features may be encompassed in a single tread element. In the illustrated embodiment, the tread element <NUM> includes a first wall <NUM>, and an edge treatment such as a rounded chamfer <NUM> extending from the second wall <NUM> to a top surface of the tread element <NUM>. The tread element further includes ratchet shaped sipes <NUM> that are disposed at an angle and proximal to the first wall <NUM>. However, it should be understood that any combination of the above embodiments may be included in a single tread element.

Claim 1:
A tire (<NUM>; <NUM>; <NUM>) having an equatorial plane, the tire (<NUM>; <NUM>; <NUM>) comprising:
a first side (120a; 320a; 520a) and a second side (120b; 320b; 520b) defining a first rotation direction (D1) and a second rotation direction (D2) of the tire (<NUM>; <NUM>; <NUM>),
wherein the first rotation direction (D1) of the tire (<NUM>; <NUM>; <NUM>) is a rotation of the tire (<NUM>; <NUM>; <NUM>) in a counterclockwise direction when the tire (<NUM>; <NUM>; <NUM>) is viewed from the first side (120a; 320a; 520a), and
wherein the second rotation direction (D2) of the tire (<NUM>; <NUM>; <NUM>) is a rotation of the tire (<NUM>; <NUM>; <NUM>) in a clockwise direction when the tire (<NUM>; <NUM>; <NUM>) is viewed from the first side (120a; 320a; 520a); and
a circumferential tread (<NUM>; <NUM>; <NUM>),
wherein the circumferential tread (<NUM>; <NUM>; <NUM>) includes a plurality of tread elements (<NUM>; <NUM>; <NUM>; <NUM>),
wherein each of the plurality of tread elements (<NUM>; <NUM>; <NUM>; <NUM>) has a plurality of angled sipes (<NUM>; <NUM>), the angled sipes (<NUM>; <NUM>) being angled, disposed therein,
wherein the plurality of angled sipes (<NUM>; <NUM>) causes the tire (<NUM>; <NUM>; <NUM>) to exhibit a first tire performance when the tire (<NUM>; <NUM>; <NUM>) is rotated in the first rotation direction (D1), and
wherein the plurality of angled sipes (<NUM>; <NUM>) causes a second tire performance that is different from the first tire performance when the tire (<NUM>; <NUM>; <NUM>) is rotated in the
second rotation direction (D2),
characterized in that
the tire performance is selected from the group consisting of braking, dry driving traction, noise, wear performance, and snow traction performance;
a first indicia (150a; 350a; 550a) is disposed on the first side (120a; 320a; 520a), including an indicator designating the first rotation direction (D1), wherein the first indicia (150a; 350a; 550a) includes an indicator designating the first rotation direction (D1) as a front tire rotation direction and the second rotation direction (D2) as a rear tire rotation direction; and
a second indicia (150b; 350b; 550b) is disposed on the second side (120b; 320b; 520b), including an indicator designating the second rotation direction (D2), wherein the second indicia (150b; 350b; 550b) includes an indicator designating the first rotation direction (D1) as a front tire rotation direction and the second rotation direction (D2) as a rear tire rotation direction.