JP7484364B2 - Method for evaluating stone-biting performance - Google Patents

Description

The present invention relates to a method for evaluating stone-biting performance.

Grooves are cut into the tread of a tire. This forms the tread pattern. When a tire runs on a road surface with stones scattered on it or on a gravel road, stones can get caught in the grooves. A groove with stones caught in it cannot function as a groove. There is a concern that stones getting caught in the grooves can locally suppress deformation of the land area, causing uneven wear. Therefore, research is being conducted with the aim of establishing technology that can prevent stones from getting caught in the grooves (for example, see Patent Document 1 below).

JP 2019-119267 A

Evaluating whether a tire's grooves are susceptible to stones getting caught, i.e., evaluating a tire's stone-trapping performance, is generally performed by running a vehicle fitted with the tires to be evaluated on a gravel road or the like. The magnitude and direction of the forces acting on the tire vary depending on where the tire is mounted. The tires to be evaluated are mounted on all wheels of the vehicle, or on the front or rear wheels of the vehicle.

When evaluating two types of tires, one tire is evaluated before the other. This evaluation method is not intended for evaluating two types of tires simultaneously. Road conditions affect the degree to which tires are trapped by stones. As road conditions change during driving, the results obtained with this evaluation method also reflect the road conditions. Various measures are taken on tires to improve their stone-trapping performance. There is a need to establish an evaluation method that can efficiently obtain comparable results so that the effectiveness of these measures can be more accurately understood.

The present invention was made in consideration of these circumstances, and aims to provide a method for evaluating stone-trapping performance that can efficiently obtain comparable results.

A method for evaluating stone-trapping performance according to one embodiment of the present invention is a method for evaluating the stone-trapping performance of a tire having a tread in which a tread pattern is formed by grooves. This evaluation method includes the following steps:
The method includes the steps of (1) running a four-wheeled vehicle equipped with the tires on a test course having a test surface containing a large number of stones, and (2) counting the number of stones that have become lodged in the grooves. The tires are a first tire and a second tire of the same tire size. The first tire is mounted on the front left and rear right sides of the four-wheeled vehicle, and the second tire is mounted on the front right and rear left sides of the four-wheeled vehicle.

Preferably, in this method for evaluating stone-trapping performance, the tread of the first tire is different from the tread of the second tire.

Preferably, in this method for evaluating stone-trapping performance, the test road surface is made of a gravel layer composed of the numerous stones. The gravel layer has a thickness of at least 15 cm.

Preferably, in this method for evaluating stone-trapping performance, the test road surface is compacted using a rolling machine prior to the running process.

The method for evaluating stone-trapping performance of the present invention allows for the efficient production of comparable results.

FIG. 1 is a development view showing an example of a first tire used in a method for evaluating stone-trapping performance according to an embodiment of the present invention. FIG. 2 is a development view showing an example of a second tire. FIG. 3 is a plan view showing an example of a test course. FIG. 4 is a cross-sectional view for explaining the configuration of the test course. FIG. 5 is a schematic diagram illustrating the mounting of tires on a four-wheeled automobile.

The present invention will now be described in detail based on a preferred embodiment, with reference to the drawings as appropriate.

In this disclosure, the state in which a tire is mounted on a standard rim, the internal pressure of the tire is adjusted to the standard internal pressure, and no load is applied to the tire is referred to as the standard state. In this disclosure, unless otherwise specified, the dimensions and angles of each part of the tire are measured in the standard state.

A genuine rim is a rim that is specified in the standard on which the tire is based. The "standard rim" in the JATMA standard, the "design rim" in the TRA standard, and the "measuring rim" in the ETRTO standard are genuine rims.

Normal internal pressure means the internal pressure specified in the standard on which the tire is based. The "maximum air pressure" in the JATMA standard, the "maximum value" listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "INFLATION PRESSURE" in the ETRTO standard are normal internal pressures. For passenger car tires, the normal internal pressure is 180 kPa unless otherwise specified.

Normal load means the load specified in the standard on which the tire is based. The "maximum load capacity" in the JATMA standard, the "maximum value" listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are normal loads. For passenger car tires, unless otherwise specified, the normal load is a load equivalent to 88% of the above load.

In this disclosure, the hardness of the elements that make up a tire and are made of crosslinked rubber is measured using a Type A durometer at a temperature of 23°C in accordance with the provisions of JIS K6253.

In this disclosure, "tire size" means the "tire designation" as defined in JIS D4202 "Automobile tires - Designation and specifications."

The method for evaluating stone-trapping performance according to one embodiment of the present disclosure is a method for evaluating the stone-trapping performance of a tire. In this evaluation method, a tire to be evaluated is mounted on a four-wheeled vehicle, and the four-wheeled vehicle is driven on a test course. After the vehicle is driven, the stone-trapping condition of the tire is confirmed. First, the tire used in this evaluation method will be described.

[tire]
In this evaluation method, the tire 2 to be evaluated is a tire 2 having a tread in which a tread pattern is formed by carving grooves. There is no particular limitation on the use of the tire 2 to be evaluated, and the tire 2 may be a tire for trucks and buses, a tire for passenger cars, or a tire for small trucks. In this evaluation method, a four-wheeled automobile is used, and the four-wheeled automobile is appropriately selected depending on the use of the tire 2 to be evaluated.

In this evaluation method, two types of tires 2 having the same tire size are prepared as tires 2 to be evaluated. In this evaluation method, one of the two types of tires 2 is referred to as the first tire 2a, and the other tire 2 is referred to as the second tire 2b. The tires 2 used in this evaluation method are the first tire 2a and the second tire 2b, which have the same tire size.

Figures 1 and 2 show examples of two types of tires 2 used in a method for evaluating stone-trapping performance according to one embodiment of the present disclosure. In this disclosure, the tire 2 shown in Figure 1 is a first tire 2a, and the tire 2 shown in Figure 2 is a second tire 2b. The first tire 2a and the second tire 2b are small truck tires.

Figure 1 shows the tread 4a of the first tire 2a. In Figure 1, the up-down direction is the circumferential direction, and the left-right direction is the axial direction. The direction perpendicular to the paper surface is the radial direction. In Figure 1, the dashed dotted line CL1 represents the equatorial plane of the first tire 2a.

The tread 4a is made of cross-linked rubber. Grooves 6a are cut into the tread 4a. This forms a tread pattern on the tread 4a.

The tread 4a of the first tire 2a is provided with grooves 6a that extend continuously in the circumferential direction, i.e., circumferential grooves 8a. This forms multiple land portions 10a in the tread 4a. These land portions 10a are arranged in parallel in the axial direction. Each land portion 10a is provided with a groove 6a that extends in the axial direction, i.e., an axial groove 12a. This forms multiple blocks 14a in the land portion 10a. These blocks 14a are arranged at intervals in the circumferential direction.

As shown in FIG. 1, four circumferential grooves 8a are formed in the tread 4a of the first tire 2a, forming five land portions 10a. The five land portions 10a are formed of a center land portion 16 located at the center in the axial direction, a pair of middle land portions 18 located outside the center land portion 16, and a pair of shoulder land portions 20 located outside the middle land portion 18. The center land portion 16 is located on the equatorial plane of the first tire 2a. Sipes 22 are formed in the blocks 14a that form the center land portion 16 and the blocks 14a that form the middle land portion 18.

Figure 2 shows the tread 4b of the second tire 2b. In Figure 2, the up-down direction is the circumferential direction, and the left-right direction is the axial direction. The direction perpendicular to the paper surface is the radial direction. In Figure 2, the dashed dotted line CL2 represents the equatorial plane of the second tire 2b.

The tread 4b of the second tire 2b is also made of crosslinked rubber. Grooves 6b are also cut into this tread 4b to form a tread pattern.

The tread 4b of the second tire 2b also has circumferential grooves 8b. This forms multiple land portions 10b in the tread 4b. Each land portion 10b has an axial groove 12b. This forms multiple blocks 14b in the land portion 10b.

As shown in FIG. 2, five circumferential grooves 8b are formed in the tread 4b of the second tire 2b, forming six land portions 10b. The five circumferential grooves 8b are formed in the axial direction by a center circumferential groove 24 located at the center, a pair of middle circumferential grooves 26 located on the outside of the center circumferential groove 24, and a pair of shoulder circumferential grooves 28 located on the outside of the middle circumferential groove 26. The center circumferential groove 24 is located on the equatorial plane of the second tire 2b. No sipes are formed in the blocks 14b that form each land portion 10b.

The tread pattern of the second tire 2b is different from the tread pattern of the first tire 2a shown in FIG. 1. The second tire 2b has the same tire size as the first tire 2a shown in FIG. 1, but has a different tread pattern. The tread 4a of the first tire 2a is different from the tread 4b of the second tire 2b.

As mentioned above, this evaluation method uses two types of tires 2 that have the same tire size. In the two types of tires 2 that are the subject of this evaluation method, the tread 4a of the first tire 2a and the tread 4b of the second tire 2b may be different. Here, examples of cases in which the tread 4a of the first tire 2a and the tread 4b of the second tire 2b are different include cases in which the tread patterns are different, cases in which the hardness of the tread 4 is different, cases in which the cross-sectional shapes of the grooves 6 that make up the tread pattern are different, cases in which there is a protrusion (not shown) at the bottom of the grooves 6 that make up the tread pattern, etc.

Although not described in detail, the tire 2 has many elements such as sidewalls in addition to the tread 4. In the two types of tires 2 targeted by this evaluation method, the configurations other than the tread 4 may be the same or different.

As mentioned above, in this evaluation method, a four-wheeled vehicle equipped with the tire 2 to be evaluated is driven on a test course to evaluate the stone-trapping performance of the tire 2. Next, the test course used in this evaluation method will be described.

[Exam Course]
An example of a test course 32 used in this evaluation method is shown in Fig. 3. This test course 32 includes a straight course portion 34 and a pair of turning course portions 36. In this disclosure, the turning course portion 36 located on one side, i.e., the right side in Fig. 3, is referred to as a first turning course portion 36a. The turning course portion 36 located on the other side, i.e., the left side, is referred to as a second turning course portion 36b.

As shown in FIG. 3, in this test course 32, a pair of turning course sections 36, i.e., a first turning course section 36a and a second turning course section 36b, are located on either side of a straight course section 34. In this test course 32, one straight course section 34 spans between the first turning course section 36a and the second turning course section 36b.

In this evaluation method, for example, the four-wheeled vehicle 38 travels from one side to the other on the straight course section 34 and enters the first turning course section 36a. The four-wheeled vehicle 38 turns on this first turning course section 36a and again enters the straight course section 34. The four-wheeled vehicle 38 travels from one side to the other on the straight course section 34 and enters the second turning course section 36b. The four-wheeled vehicle 38 turns on this second turning course section 36b and again enters the straight course section 34. In this evaluation method, the four-wheeled vehicle 38 travels in order on the straight course section 34, the first turning course section 36a, the straight course section 34, and the second turning course section 36b, so that the four-wheeled vehicle 38 has traveled one lap around the test course 32.

In this test course 32, the straight ahead driving mode, left turning driving mode, and right turning driving mode are executed as driving modes of the four-wheeled vehicle 38 by turning in the second turning course section 36b in the opposite direction to the turning driving in the first turning course section 36a. This test course 32 is configured so that the tire 2 can experience all of the driving modes of the four-wheeled vehicle 38.

Figure 4 shows a cross section of the test course 32 together with a four-wheeled vehicle 38 traveling on the test course 32. As shown in Figure 4, the test course 32 comprises a base layer 40 and a gravel layer 42 laminated on the base layer 40. The base layer 40 is a leveled ground. The base layer 40 is also called a roadbed. The gravel layer 42 is a layer having a predetermined thickness and made up of a large number of stones. In the test course 32, the test road surface 44 is made up of the gravel layer 42. The gravel layer 42 contains a large number of stones. The test course 32 has a test road surface 44 containing a large number of stones.

In this evaluation method, the gravel layer 42 may be formed by scattering a large number of stones on the base layer 40, or after scattering a large number of stones on the base layer 40, the gravel layer 42 may be formed by compacting the stones with a rolling machine (not shown) such as a plate compactor, rammer, or roller.

In this evaluation method, there are no particular restrictions on the stones used in the gravel layer 42, so long as they are large enough to be embedded in the grooves 6 of the tire 2. In this evaluation method, from the standpoint of ease of embedding in the grooves 6, stones having a size of 1 mm or more and 10 mm or less are preferably used as stones in the gravel layer 42.

In this evaluation method, the stone-trapping performance of the tire 2 is evaluated using the tire 2, the test course 32, and the four-wheeled vehicle 38 on which the tire 2 is mounted, as described above. Next, this evaluation method will be described.

[Evaluation method]
In this evaluation method, the tire 2 to be evaluated is mounted on a four-wheeled automobile 38. This evaluation method includes a process of mounting the tire 2 on the four-wheeled automobile 38. In this mounting process, the tire 2 is assembled onto a rim. Air is filled inside the tire 2, and the internal pressure of the tire 2 is adjusted. After the adjustment, the rim 46 is attached to the four-wheeled automobile 38. This completes the mounting of the tire 2 on the four-wheeled automobile 38.

In this evaluation method, a standard rim is used as the rim 46 on which the tire 2 is mounted. The internal pressure of the tire 2 is usually adjusted to the standard internal pressure, but this internal pressure may be set to a pressure lower than the standard internal pressure or may be set to a pressure higher than the standard internal pressure.

In this evaluation method, once the tire 2 has been fitted to the four-wheeled vehicle 38, the four-wheeled vehicle 38 fitted with the tire 2 is driven on the test course 32. This evaluation method includes a process of driving the four-wheeled vehicle 38 fitted with the tire 2 on the test course 32. In this evaluation method, the four-wheeled vehicle 38 is driven at a predetermined speed. When the driving distance reaches a predetermined distance, the driving of the four-wheeled vehicle 38 is stopped. This completes the driving process.

In this evaluation method, the number of passengers in the four-wheeled vehicle 38 is usually one (driver only), but the number of passengers may be two or more. If the four-wheeled vehicle 38 has a luggage compartment, luggage may be loaded on the four-wheeled vehicle 38. In this evaluation method, the load acting on the tire 2 is adjusted appropriately according to the number of passengers or the amount of luggage loaded, as long as it does not exceed the normal load.

In this evaluation method, when the driving process is completed, the number of stones caught in the grooves 6 of the tire 2 is counted. This evaluation method includes a process of counting the number of stones caught in the grooves 6. In this evaluation method, the stone-trapping performance of the tire 2 is evaluated based on the counting result. The more stones caught in the grooves 6, the more likely it is that stones will become caught in the grooves 6. In other words, a tire 2 with a smaller number of stones caught in the grooves 6 has excellent stone-trapping resistance.

As described above, the tires 2 to be evaluated are the first tire 2a and the second tire 2b, which have the same tire size. In this evaluation method, the first tire 2a and the second tire 2b to be evaluated are mounted on a four-wheeled automobile 38. In this evaluation method, two types of tires 2 are evaluated simultaneously.

Figure 5 shows the mounting position of the tire 2 to be evaluated. In this Figure 5, the upper side is the front side of the four-wheeled vehicle 38. Figure 5(a) shows an example of mounting the tire 2 to a four-wheeled vehicle 38 whose front and rear wheels each consist of a single tire. Figure 5(b) shows an example of mounting the tire 2 to a four-wheeled vehicle 38 whose front wheels consist of a single tire and whose rear wheels consist of double tires.

As shown in FIG. 5, in this evaluation method, the first tire 2a is mounted on the front left and rear right of the four-wheeled vehicle 38, and the second tire 2b is mounted on the front right and rear left of the four-wheeled vehicle 38.

In this evaluation method, tires 2 are mounted on a four-wheeled vehicle 38 such that the types of tires 2 mounted on the left and right sides of the front and rear of the four-wheeled vehicle 38 are different. Therefore, even if the tires 2 differ in how easily they become clogged with stones, tires 2 that are prone to becoming clogged with stones and tires 2 that are not prone to becoming clogged with stones are located on both the left and right sides of the four-wheeled vehicle 38. Tires 2 that are prone to becoming clogged with stones and tires 2 that are not prone to becoming clogged with stones are located on both the front and rear of the four-wheeled vehicle 38.

This evaluation method effectively reduces the impact of stones getting caught in the tires 2 on the running state of the four-wheeled vehicle 38 compared to a case where the first tires 2a are mounted on both the front left and right sides and the second tires 2b are mounted on both the rear left and right sides, or a case where the first tires 2a are mounted on both the front and rear sides of the left side and the second tires 2b are mounted on both the front and rear sides of the right side. This evaluation method efficiently provides comparable results regarding the stone-trapping performance of the tires 2.

In Figure 4, the double-headed arrow T represents the thickness of the gravel layer 42 that constitutes the test road surface 44. This thickness T is represented by the minimum thickness of the gravel layer 42.

In this evaluation method, the test road surface 44 is made of a gravel layer 42 composed of many stones, and it is preferable that this gravel layer 42 has a thickness of at least 15 cm. This prevents the gravel layer 42 from collapsing during driving, and allows the tread 4 of the tire 2 to continue to be in stable contact with the stones contained in the test road surface 44. In a tire 2 in which stones are likely to get stuck in the grooves 6, the stones are encouraged to get stuck in the grooves 6. This evaluation method efficiently obtains comparable results regarding the stone-biting performance of the tire 2. From this perspective, the thickness T of the gravel layer 42 is more preferably 17 cm or more, and even more preferably 19 cm or more. From the perspective of easy maintenance of the gravel layer 42, this thickness T is preferably 25 cm or less.

In this evaluation method, it is preferable to compact the test road surface 44 using the above-mentioned rolling machine before the running process, from the viewpoint of preventing the collapse of the gravel layer 42 due to running and enabling the tread 4 of the tire 2 to continue to be in stable contact with the stones contained in the test road surface 44. In particular, by having the gravel layer 42 of the test road surface 44 compacted using the rolling machine have a thickness of at least 15 cm, it is possible to effectively prevent the collapse of the gravel layer 42 due to running, and to enable the tread 4 of the tire 2 to continue to be in more stable contact with the stones contained in the test road surface 44. This evaluation method can efficiently obtain comparable results regarding the stone-biting performance of the tire 2.

When this evaluation method is performed using the test course 32 shown in FIG. 3, as described above, the straight running mode, left turning running mode, and right turning running mode are executed as the running modes of the four-wheeled vehicle 38 by turning in the second turning course section 36b in the opposite direction to the turning running in the first turning course section 36a. In this case, the lateral acceleration and the longitudinal acceleration act almost equally on each tire 2 of the four-wheeled vehicle 38. In this evaluation method, the bias of the lateral acceleration and the longitudinal acceleration acting on the tire 2 mounted on the four-wheeled vehicle 38 is suppressed compared to the case where an oval course is adopted as the test course 32. In this evaluation method, it is possible to efficiently obtain comparable results regarding the stone-trapping performance of the tire 2. From this viewpoint, in this evaluation method, it is preferable that the test course 32 has a straight course section 34 and a pair of turning course sections 36 located on both sides of the straight course section 34. In this case, it is more preferable that the four-wheeled vehicle 38 is caused to turn so that the directions of the four-wheeled vehicle 38 turn in the turning course sections 36 are opposite to each other.

In FIG. 3, the double-headed arrow S represents the distance of the straight course section 34. The arrow R represents the minimum turning radius of the four-wheeled vehicle 38 when the four-wheeled vehicle 38 turns on the turning course section 36. On the turning course section 36, the four-wheeled vehicle 38 runs outside the circular path represented by the minimum turning radius R.

In this evaluation method, it is preferable that the straight course section 34 has a distance S of at least 50 m. This allows this evaluation method to efficiently obtain comparable results regarding the stone-trapping performance of the tires 2. From this perspective, it is more preferable that this distance S is 60 m or more, and even more preferable that this distance S is 70 m or more. From the perspective of obtaining comparable results, the longer the distance S, the better, but from the perspective of easy maintenance of the test course 32, it is preferable that this distance S is 200 m or less.

In this evaluation method, the minimum turning radius R of the four-wheeled vehicle 38 in the turning course section 36 is preferably 10 m or less. This applies a moderate lateral acceleration to the tires 2 mounted on the four-wheeled vehicle 38, encouraging stones to be trapped in the grooves of tires 2 that are prone to trapping stones. This evaluation method efficiently obtains comparable results regarding the stone trapping performance of tires 2. From this perspective, the minimum turning radius R is more preferably 9 m or less, and even more preferably 8 m or less. The preferable lower limit of the minimum turning radius R is determined appropriately, taking into consideration the minimum turning radius of the four-wheeled vehicle 38 used in the evaluation method.

In this evaluation method, there is no particular restriction on the running speed of the four-wheeled vehicle 38 during the running process, so long as stone trapping can be reproduced. From the viewpoint of promoting stone trapping in the grooves 6, it is preferable for the four-wheeled vehicle 38 to be run at a low speed. Specifically, the running speed of the four-wheeled vehicle 38 is preferably 40 km/h or less, and more preferably 30 km/h or less. From the viewpoint of efficiently obtaining comparable data regarding stone trapping performance, this running speed is preferably 5 km/h or more, and more preferably 10 km/h or more.

In this evaluation method, as long as stone trapping can be reproduced, there is no particular restriction on the distance traveled by the four-wheeled vehicle 38 during the travel process. From the viewpoint of promoting stone trapping in the grooves 6, the longer the travel distance of the four-wheeled vehicle 38, the better. Specifically, the travel distance of the four-wheeled vehicle 38 is preferably 1.0 km or more, and more preferably 1.5 km or more. From the viewpoint of efficiently obtaining comparable data regarding stone trapping performance, this travel distance is preferably 5.0 km or less, and more preferably 3.0 km or less.

As described above, the present invention provides a method for evaluating stone-trapping performance that can efficiently obtain comparable results.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[Example]
As two types of tires to be evaluated, a first tire (tire size = 205/85R16) having a tread shown in Figure 1 and a second tire (tire size = 205/85R16) having a tread shown in Figure 2 were prepared. The first tire and the second tire are commercially available tires, and it has been confirmed that the grooves of the second tire tend to be more susceptible to stone getting caught than the first tire.

The first tire was mounted on a standard rim, and the internal pressure of the first tire was adjusted to the standard internal pressure. The second tire was mounted on a standard rim, and the internal pressure of the second tire was adjusted to the standard internal pressure. After adjusting the internal pressure, the first tire and the second tire were mounted on a four-wheeled vehicle (10-ton truck). The mounting positions of the first tire and the second tire are as shown in Figure 5 (b).

The test course used was the one shown in Figure 3. The distance S of the straight course section of the test course was set to 60 m. The tight turning radius R of the turning course section was set to 5 m. In the turning course section, the four-wheeled vehicle ran outside the path represented by a circle with a radius R of 5 m. The test road surface of this test course consisted of a gravel layer, which was composed of numerous stones with sizes ranging from 1 to 10 mm. Before the running process, the gravel layer was compacted using a rolling machine (roller). The minimum thickness of the gravel layer was set to 15 cm.

A four-wheeled vehicle fitted with the tires was driven on a test course to evaluate the stone-trapping performance of the first and second tires. The driving speed was set to 20 km/h. The driving distance was set to 2.0 km. After driving, the number of stones trapped in the tire grooves was counted. The results are shown in Table 1 below. The smaller the value, the fewer the number of stones trapped in the grooves, indicating superior stone-trapping resistance. The number of stones on the rear wheels is expressed as the average value of the two tires fitted to the rear wheels.

As shown in Table 1, for the front wheels, the number of stones trapped in the second tire was 4.0 times that of the first tire. For the rear wheels, the number of stones trapped in the second tire was 3.5 times that of the first tire. The stone-trapping performance of the second tire is inferior to that of the first tire. This result is consistent with the trends observed in actual use.

In the conventional evaluation method, in which a first tire or a second tire is fitted to each wheel of a four-wheeled vehicle, two driving tests must be performed to obtain comparable results. In contrast, with this evaluation method, comparable results can be obtained with a single driving test. This evaluation method allows for efficient obtaining of comparable results. Moreover, this evaluation method allows for quantitative evaluation of stone-trapping performance results. The advantages of the present invention are clear.

The method for evaluating stone-trapping performance described above can be applied to a variety of tires.

2, 2a, 2b... Tire 4, 4a, 4b... Tread 6, 6a, 6b... Groove 8a, 8b... Circumferential groove 10a, 10b... Land portion 12a, 12b... Axial groove 14a, 14b... Block 16... Center land portion 18... Middle land portion 20... Shoulder land portion 22... Sipe 24... Center circumferential groove 26... Middle circumferential groove 28... Shoulder circumferential groove 32... Test course 34... Straight course portion 36, 36a, 36b... Turning course portion 38... Four-wheeled vehicle 40... Base layer 42... Gravel layer 44... Test road surface 46... Rim

Claims (6)

A method for evaluating the stone-biting performance of a tire having a tread having a tread pattern formed by grooves, comprising:
A step of running a four-wheeled vehicle equipped with the tire on a test course having a test surface including a large number of stones;
and counting the number of stones caught in the grooves.
the tires are a first tire and a second tire having the same tire size,
The first tires are mounted on the front left and rear right of the four-wheeled vehicle,
The second tires are mounted on the front right side and the rear left side of the four-wheeled vehicle ,
The test course includes a straight course portion and a pair of turning course portions located on both sides of the straight course portion,
In the traveling step, the four-wheeled vehicle is caused to make a turn so that the directions of the four-wheeled vehicle's turning on the turning course portion are opposite to each other on each turning course portion . The method for evaluating stone-trapping performance according to claim 1, wherein the tread of the first tire and the tread of the second tire are different. The test road surface is made of a gravel layer composed of the plurality of stones,
3. The method for evaluating stone-biting performance according to claim 1 or 2, wherein the gravel layer has a thickness of at least 15 cm. The method for evaluating stone-trapping performance according to any one of claims 1 to 3, wherein the test road surface is compacted using a rolling machine before the running process. The method for evaluating stone-trapping resistance according to claim 1 , wherein a travel distance of the four-wheeled automobile in the travel step is 1.0 km or more and 5.0 km or less. 6. The method for evaluating stone-trapping performance according to claim 1, wherein the distance of the straight course portion is 50 m or more and 200 m or less, and the minimum turning radius of the four-wheeled vehicle in the previous turning course portion is 10 m or less.

Images