JP6512661B2 - Tire Durability Test Method - Google Patents

Description

  The present invention relates to a method of evaluating the durability of a tire. In particular, it relates to a method of evaluating bead durability.

  The tire is run on a drum and the bead bead durability is evaluated. This evaluation method is not affected by the weather and can be evaluated under certain conditions. This evaluation method can obtain evaluation results with small variations. In this evaluation method, the durability of the bead is evaluated by the running time until damage to the bead occurs. In this evaluation method, a large load is loaded on the tire in order to promote bead damage. However, the travel time until damage to the bead occurs is long. In particular, in a tire with improved bead durability, such as a heavy duty tire, this travel time is even longer.

  In addition, heavy duty tires are used under severe conditions. As such heavy load tires, there are, for example, truck and bus tires. Heavy duty tires are used under heavy load. Heavy-duty tires are often used in traveling in mountainous areas where there are many ups and downs. A brake may be used abundantly in such a run. In such traveling, heat generated during braking (hereinafter referred to as brake heat) is large. The brake heat heats the rim flange. The brake heat promotes damage to the bead through the rim flange. In order to evaluate the bead durability in the market with high accuracy, it is necessary to evaluate the bead durability also taking into consideration the influence of the brake heat.

  The test device which evaluates the endurance of a tire is indicated by JP, 2013-257190, A. The test apparatus evaluates durability while heating around the bead of the tire. The test apparatus promotes deterioration around the bead by this heating. In the evaluation method using this test device, the travel time until damage to the bead can be shortened. In this evaluation method, the bead durability can be evaluated in consideration of the influence of the brake heat.

JP, 2013-257190, A

  In the test device of JP2013-257190A, a heater is disposed around a rim flange of a running tire. In the evaluation method using this test apparatus, it is necessary to adjust the position of the heater. Also, depending on the form of bead damage, the heater may be damaged.

  On the other hand, there is an evaluation method of thermally deteriorating the tire in advance. In this evaluation method, a tire assembly in which a tire is incorporated in a rim is heated by an oven or the like. The heated tire assembly travels over the drum to evaluate bead durability. In this evaluation method, since the tire is thermally deteriorated in advance, the running time is short. Depending on the object of evaluation of the durability of the bead, the heater is not required by thermal degradation in advance.

  The inventors found from the results of various tests that in the case of a tire that has been thermally deteriorated in advance, the evaluation results of bead durability are likely to vary. The variation in the evaluation result reduces the accuracy of the evaluation.

  An object of the present invention is to provide a method of evaluating the durability of a tire which can evaluate the durability of a bead with high accuracy and in a short time.

The method for evaluating the durability of a tire according to the present invention is
A heating step in which the tire assembly in which the tire is incorporated into the rim is heated;
A rim detaching step in which the tire is removed from the rim after the heating step and is incorporated again into the rim or another rim;
And a traveling step in which the tire assembly after the rim attaching and detaching step is caused to travel.

  The evaluation method according to claim 1, wherein preferably, in the heating step, the heating temperature Th of the tire assembly is set to the highest attainable temperature of the bead of the market tire.

  Preferably, in the heating step, the heating temperature Th of the tire assembly is 90 (° C.) or more and 110 (° C.) or less under dry heat.

  Preferably, in the heating step, the heating period Ph of the tire assembly is from 1 day to 5 days under dry heat.

Preferably, in the heating step, the heating temperature Th of the tire assembly and the heating period Ph of the tire assembly are the inner diameter change amount Dc of the bead toe of the tire and the inner diameter change amount Dr of the bead toe of the market tire. It is set to satisfy the following equation (mm).
The inner diameter change amount Dc is a value obtained by subtracting the inner diameter of the bead toe before the heating step from the inner diameter of the bead toe after the heating step. The inner diameter change amount Dr is a value obtained by subtracting the inner diameter of the unused bead toe from the inner diameter of the bead toe of the tire which has reached the useful life on the market.
(Dr-1) ≦ Dc ≦ (Dr + 1)

  Preferably, in the heating step, the heating temperature Th of the tire assembly and the heating period Ph of the tire assembly are such that the inner diameter variation Dc of the bead toe of the tire is 10 (mm) or more and 17 (mm) or less Is set.

Preferably, the evaluation method includes a determination step of determining whether the tire is acceptable or not. The longest traveling time at which the traveling process ends and a reference time shorter than the longest traveling time are set.
In the determination step, the traveling time of the tire in the traveling step is compared with the reference time to make a pass determination.

  The evaluation method according to the present invention includes the heating step. By providing the heating step, it is possible to evaluate the bead durability close to the market evaluation. Moreover, the travel time in the travel process is shortened by providing the heating process. Furthermore, the variation in the evaluation result is suppressed by providing the rim desorption process between the heating process and the traveling process. This method can evaluate bead durability evaluation with high accuracy and in a shorter time than in the past.

FIG. 1 is a conceptual view showing a test machine for an evaluation method according to an embodiment of the present invention. FIG. 2 is a front view of a tie or the like to be evaluated by the method of FIG.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the drawings as appropriate.

  An example of the traveling test machine 2 is shown in FIG. The tester 2 is used in the method of evaluating the durability of a tire according to the present invention. In FIG. 1, a tire 4 which is a test tire is also shown. Although not shown, the tire 4 is incorporated in the rim. The traveling test machine 2 includes a rim support 6, a drive drum 8, a temperature sensor 12, and a controller 14. The direction perpendicular to the paper surface of FIG. 1 is the front-rear direction of the tester 2. The vertical direction and the horizontal direction in FIG. 1 correspond to the vertical direction and the horizontal direction of the tester 2.

  The rim support 6 supports the rim on which the tire 4 is mounted. The rim support 6 rotates the rim. The rim support 6 brakes the rotation of the rim. The rim support 6 can decelerate the rotation of the tire 4 and stop the rotation of the tire 4. The rim support 6 moves vertically with respect to the drive drum 8. By this movement, the tire 4 is made movable between a position contacting the driving drum and a position away from the driving drum. The rim support 6 can press the tire 4 mounted on the rim against the drive drum 8 with a predetermined load. The rim support 6 is electrically connected to the control unit 14.

  The drive drum 8 is cylindrical. The outer peripheral surface of the drive drum 8 constitutes a traveling surface on which the tread surface of the tire 4 comes in contact with the ground. As the drive drum 8 rotates, the tire 4 that is in contact with the ground rotates. The rotation of the drive drum 8 causes the tire 4 to travel. The rotational speed of the drive drum 8 is adjustable. The traveling speed of the tire 4 is adjustable. The drive drum 8 is electrically connected to the control unit 14.

  The temperature sensor 12 is mounted near the flange of the rim. The temperature sensor 12 measures the temperature of the tire 4 in the vicinity of the rim flange. The temperature sensor 12 is electrically connected to the control unit 14. The temperature sensor 12 transmits measurement data to the control unit 14. Although not shown, a heater may be further provided. A heater may be arranged to heat around the bead of the tire traveling the drum.

  The control unit 14 controls the rim support 6 and the drive drum 8. The control unit 14 receives temperature data measured by the temperature sensor 12. The control unit 14 controls the rim supporting unit 6 and the driving drum 8 so that the tire 4 travels under traveling conditions such as a preset load, traveling speed, traveling time, and the like. The control unit 14 may control a heater (not shown) to heat the bead bead periphery of the tire based on temperature data of the temperature sensor 12.

  The tire 4 of FIG. 2 is not built into the rim. The direction perpendicular to the sheet of FIG. 2 is the axial direction of the tire 4. Although not shown, the tire 4 includes a tread, a pair of sidewalls, a pair of clinch, a pair of beads, a carcass, a belt, an inner liner, and a pair of chafers. Although not shown, the tire 4 has a substantially symmetrical shape in the axial direction of the tire 4. The tire 4 is a tubeless type. The tire 4 is mounted on a truck, a bus or the like. The tire 4 is a heavy load tire.

  The tread forms a tread surface that comes in contact with the road surface. The sidewall absorbs the impact from the road surface by bending. This sidewall prevents carcass injury. The bead comprises a core and an apex extending radially outwardly from the core. The core is ring-shaped and comprises wound non-stretchable wire. The typical material of the wire is steel. The apex is tapered radially outward. This apex is made of a highly hard crosslinked rubber. When the tire 4 is incorporated into the rim, the bead causes the tire 4 to be fitted to the rim.

  The carcass consists of a carcass ply. The carcass ply is bridged between the beads on both sides and is along the tread and sidewalls. The carcass ply is folded back from the inside to the outside in the axial direction around the core. The main portion and the folded portion are formed in the carcass ply by the folding. The carcass constitutes the skeleton of the tire 4.

  The clinch is located approximately radially inward of the sidewall. The clinch extends radially inward from the radially inner portion of the sidewall. The chafer is located near the bead. The chafer is located radially inward of the bead. In the tire 4, the chafer is integrated with the clinch. When the tire 4 is incorporated into the rim, the clinch abuts on the rim flange. The chafer abuts against the seat surface of the rim. The clinch and the chafer protect the bead against the rim. The pointed end of the radially inner end of this chafer is a bead toe. The double arrow DT in FIG. 2 represents the inner diameter of this bead toe.

  The method of evaluating the durability of a tire according to the present invention will be described using the tester 2 and the tire 4 of FIG. This method comprises a heating step, a rim desorption step, a traveling step, and a determination step.

  In the heating process, the tire 4 is incorporated into the rim to prepare a tire assembly. This rim is the regular rim of the tire 4. The tire assembly is filled with air of normal internal pressure. The tire assembly is heated at a preset heating temperature Th and a heating period Ph. The tire 4 is thermally degraded under dry heat. In the present invention, heating and thermally degrading in an atmosphere of dry air is referred to as thermal degradation under dry heat. For example, the tire assembly may be placed in a dry heat oven (an oven in which no moisture is injected) and heated. After this heating, the tire assembly is allowed to return to ambient temperature.

  In the rim removal step, the rim is removed from the tire 4 after the heating step. After the rim is removed, the tire 4 is incorporated into the rim again. The rim used in the heating step and the rim on which the tire 4 is incorporated again may be the same rim or different rims. In these rims, the shape of the portion where the tire 4 abuts may be the shape of a regular rim.

  In the traveling process, the tire assembly after the rim removal process is traveled by the tester 2. The tread surface of the tire 4 is in contact with the outer peripheral surface of the drive drum 8 and is rotated. This traveling step is performed, for example, in a room at 25 (° C.). The traveling speed of the tire 4 is set to, for example, 20 (km / h). The traveling process includes a first traveling process, a second traveling process, and a third traveling process. In this traveling process, the air pressure and load load of the second traveling process are larger than those of the first traveling process. The air pressure and load of the third traveling step are made larger than those of the second traveling step. In this traveling process, the test conditions are strict in the order of the first traveling process, the second traveling process, and the third traveling process.

  In the first traveling step, for example, the air pressure is set to a normal internal pressure. For example, a load of 235% of the normal load is applied to the tire 4. The longest travel time is set to, for example, 96 hours. If damage to the bead 4 of the tire 4 is confirmed within the longest travel time, the traveling process ends when the bead 4 is confirmed. If the damage can not be confirmed within the longest traveling time, the first traveling process is ended, and the process proceeds to the second traveling process.

  In the second traveling step, for example, the air pressure is increased by 150 (kPa) to the normal internal pressure. For example, a load of 270% of the normal load is applied to the tire 4. The longest travel time is, for example, 96 hours. If damage to the bead 4 of the tire 4 is confirmed within the longest travel time, the traveling process ends when the bead 4 is confirmed. If the damage can not be confirmed within the longest travel time, the second travel process is ended, and the process proceeds to the third travel process.

  In the third traveling step, for example, the air pressure is increased by 200 (kPa) to the normal internal pressure. For example, a load of 300% of the normal load is applied to the tire 4. The longest travel time is, for example, 96 hours. If damage to the bead 4 of the tire 4 is confirmed within the longest travel time, the traveling process ends when the bead 4 is confirmed. If the damage can not be confirmed within the longest traveling time, the third traveling step is ended. This third traveling process may be continued until the bead 4 of the tire 4 is damaged without setting the longest traveling time.

  In the determination step, the bead durability of the tire 4 is evaluated. For example, in this determination step, durability pass / fail determination is performed. The longest travel time is set in this travel process. The longest traveling time is a time obtained by adding the longest traveling times of the first traveling process, the second traveling process, and the third traveling process. A reference time shorter than the longest travel time of this travel process is set. If the traveling time of the tire 4 is equal to or greater than this reference time in the traveling step, the acceptance determination of the tire 4 is performed in the determination step. On the other hand, if the running time of the tire 4 is less than the reference time, rejection of the tire 4 is determined in the determination step.

  This reference time is determined by the master tire which becomes the acceptance standard of bead durability. About this master tire, the evaluation method of the endurance concerning the present invention is carried out on the same conditions as the above-mentioned tire 4. The heating temperature Th and the heating period Ph of the heating process are set so that the bead of the master tire is damaged at a reference time shorter than the longest traveling time of the traveling process.

  In this determination process, the longest traveling time of the traveling process and the reference time are set. By making the reference time sufficiently shorter than the longest running time, it is possible to more reliably determine the durability of the tire 4. From the viewpoint of ensuring the pass / fail determination, it is preferable that the difference between the longest traveling time of the traveling process and the reference time be large. The difference is preferably 20 hours or more, more preferably 30 hours or more, and particularly preferably 80 hours or more.

  In the heating step of this evaluation method, the tire assembly is heated. The tire 4 receives gravity. For example, in a standing tire assembly in which the tread surface is in contact with the ground, deflection is likely to occur around the bead in the radially inner portion of the tread surface to be in contact with the ground. In the tire 4, distortion is likely to occur in the radial direction inner portion of the tread surface in contact with the ground in the circumferential direction. In this tire 4, this distortion is biased in the circumferential direction.

  This evaluation method comprises a rim desorption step after the heating step. The tire 4 after the heating step is removed from the rim. By removing the rim, distortion generated in the tire 4 is alleviated. This alleviates circumferentially biased distortion. In this tire assembly, the circumferentially biased distortion around the bead is alleviated by detaching the rim. This reduction reduces the variation in travel time of the travel process. This relaxation suppresses variations in the evaluation of bead durability. This rim attachment and detachment process contributes to the improvement of the evaluation accuracy of the durability.

  Since this rim desorption process is provided, variation in travel time of the travel process is reduced. Thereby, even if the difference between the longest travel time of the determination step and the reference time is short, it can be determined whether the durability of the tire 4 is good or bad. In this evaluation method, when the durability of the tire 4 is determined to be pass / fail based on the durability of the master tire, the determination accuracy is improved.

  The evaluation of the durability of this determination step may be comparative evaluation. For example, in addition to the tire 4, a plurality of test tires are prepared. The durability evaluation method according to the present invention is also implemented on these test tires under the same conditions as the tire 4. The running time in the running step is compared between the tire 4 and the plurality of other test tires. It is evaluated that the longer the traveling time in this traveling process, the better the durability. The tire 4 and the plurality of other tires may be ranked in durability based on the traveling time.

  The maximum attainable temperature of the bead by use in the market varies depending on the use environment of the tire 4. As a result of investigations in various markets, this maximum achieved temperature is in the range of approximately 90 (° C.) to 110 (° C.). In the heating step, the heating temperature Th of the tire assembly is preferably set to the highest attainable temperature of the beads on the market. In other words, the heating temperature Th of the tire assembly is preferably set to the highest attainable temperature of the bead of the tire 4 used on the market (hereinafter referred to as market tire 4). This gives an evaluation result close to the durability of the market bead. From this viewpoint, the heating temperature Th is preferably 90 (° C.) or more. The heating temperature Th is preferably 110 (° C.) or less.

  Preferably, the highest attainable temperature is measured under the environment where the tire 4 is actually used. The heating temperature Th in the heating step is set to this maximum temperature. As a result, an evaluation result closer to the durability in the market where the tire 4 is used can be obtained. This evaluation method can contribute to the development of the tire 4 most suitable for the environment actually used in the durability of the bead.

  The highest attainable temperatures of the beads on the market are measured, for example, by means of temperature measuring seals. A tire assembly having a temperature measuring seal affixed to the rim is prepared. The tire assembly is mounted on a vehicle. The vehicle travels under the actual use environment, and the maximum temperature reached is measured. The temperature measurement seal is, for example, one in which the display appears when the temperature of the pasting surface reaches a predetermined temperature. The temperature measurement seal may be one in which a display corresponding to the temperature of the pasting surface appears or one in which a color corresponding to the temperature of the pasting surface appears. The temperature of the bead is about 30 (° C.) lower than that of the rim. Therefore, in this temperature measurement, if the temperature of the rim is 140 (° C.), the temperature of the bead can be estimated to be 110 (° C.).

  In the heating step in which the heating period Ph is short, a difference in the degree of thermal deterioration easily occurs in the circumferential direction of the bead. The difference in the degree of thermal deterioration promotes the variation of the traveling time in the traveling process. The heating period Ph is preferably one day, and more preferably two days or more, from the viewpoint of suppressing the variation in the evaluation results of the durability of the bead. On the other hand, in the heating step where the heating period Ph is too long, thermal degradation of the bead proceeds too much. When the thermal degradation of the bead proceeds too much, it is difficult to cause a difference in running time due to the durability of the bead. When the thermal degradation of the bead proceeds too much, the difference in running time between the bead having excellent durability and the bead having poor durability is small. In this respect, the heating period Ph is preferably within 5 days, more preferably within 4 days.

  By bringing the state of thermal deterioration of the bead of the tire 4 closer to the state of thermal deterioration of the bead on the market, the bead durability on the market can be evaluated with high accuracy. In this method, by devising the heating conditions of the heating process, it is possible to evaluate the bead durability on the actual market with high accuracy. As a method of approaching the state of thermal degradation of the beads on the market, the heating conditions of the heating process are set so that the inner diameter change amount Dc of the bead toe in the heating step becomes equal to the inner diameter change Dr of the bead toe on the market. There is a way.

  In this method, tires 4 used in the market are recovered. This market tire 4 is a tire 4 that has actually been used and has reached the useful life. The inner diameter D1 of the bead toe of this market tire 4 is measured. The inside diameter D1 is measured by a bead toe on the rim flange side, which has a high temperature in actual use, of the pair of rim flanges. The inner diameter DT of the bead toe of the new tire 4 is subtracted from the inner diameter D1, and the inner diameter change amount Dr of the market tire 4 is calculated. The inner diameter change amount Dr is calculated as an average value of the market tires 4.

  The inner diameter DH of the bead toe of the tire 4 after the heating step of this evaluation method is measured. The inner diameter DT is subtracted from the inner diameter DH, and the inner diameter change amount Dc of the tire 4 after the heating step is calculated. The inner diameter change amount Dc is calculated as an average value of the tire 4 after the heating step.

  In the heating step, the durability of the bead can be evaluated appropriately and efficiently by setting the heating condition so that the amount of change in inner diameter Dc of the bead toe becomes an appropriate amount. From this viewpoint, the inner diameter change amount Dc is preferably 10 mm or more. The inner diameter change amount Dc is preferably 17 mm or less. In the heating step, preferably, the heating temperature Th and the heating period Ph are set such that the inner diameter change amount Dc falls within this range.

The heating conditions of the heating process are adjusted such that the inner diameter change amount Dc satisfies the following relational expression with the inner diameter change amount Dr. In this equation, the inner diameter change amount Dc is an inner diameter (Dr-1) (mm) or more smaller than the inner diameter change amount Dr by 1 (mm) and the inner diameter (Dr + 1) (mm) larger than the inner diameter change amount Dr by 1 (mm) It is below.
(Dr-1) ≦ Dc ≦ (Dr + 1)

  As a heating condition of this heating step, one or both of the heating temperature Th and the heating period Ph are adjusted. For example, the heating temperature Th is set to the highest reached temperature of the portion around the bead on the market, and the heating period Ph is adjusted. A period in which the inner diameter change amount Dc and the inner diameter change amount Dr satisfy the above relational expression is set as the heating period Ph. As a result, evaluation results closer to market bead durability can be obtained.

  In this evaluation method, the bead durability is evaluated. There are two types of damage to the bead: ply turn-up loose (hereinafter referred to as PTL) and bead blow-out damage. PTL is a form of damage in which the folded end of the carcass ply peels off. Bead blow through damage is a form of damage in which the carcass ply comes off the core.

  The load applied to the tire 4 and the brake heat affect the occurrence of PTL and bead blow through damage. The occurrence of PTL is more affected by applied load than bead blow through damage. The occurrence of bead blow-through damage is more affected by brake heat than PTL. By adjusting the heating temperature Th and the heating period Ph in the heating step, the ease of occurrence of PTL of the tire 4 can be evaluated. By adjusting the heating temperature Th and the heating period Ph, the easiness of occurrence of bead blow through damage of the tire 4 can be evaluated. For example, in this method, the heating temperature Th and the heating period Ph may be adjusted so that PTL occurs in the traveling step of the master tire. The heating temperature Th and the heating period Ph may be adjusted so as to cause bead blowout damage in the traveling step of the master tire, and heating may be further performed in the traveling step.

  In the present specification, the normal rim means the rim defined in the standard on which the tire 4 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 regular rims. The normal internal pressure means the internal pressure defined in the standard on which the tire 4 relies. The “maximum air pressure” in the JATMA standard, the “maximum value” published in the “TIRE LOAD LIMITS AT VARIOUS COLD INFlation PRESSURES” in the TRA standard, and the “INFLATION PRESSURE” in the ETRTO standard are normal internal pressure. The normal load means the load defined in the standard on which the tire 4 is based. The "maximum load capacity" in the JATMA standard, the "maximum value" published in the "TIRE LOAD LIMITS AT VARIOUS COLD INFlation PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are normal loads.

  Hereinafter, the effects of the present invention will be clarified by examples, but the present invention should not be interpreted in a limited manner based on the description of the examples.

  As tires to be subjected to the test, a tire A having excellent bead durability on the market and a tire B having bead durability inferior to the tire A were prepared. The size of each tire is 11R22.5SP521. Each tire was incorporated into a standard rim (size = 22.5 × 7.50) and filled with air so as to obtain a normal internal pressure (800 (kPa)).

Example 1
The durability of the bead of the tire A was evaluated by the evaluation method according to the present invention. The heating temperature Th of the heating step was 110 (° C.), and the heating period Ph was 3 days. In the traveling process, the tester shown in FIG. 1 was used. The evaluation in Table 1 was conducted on three tires.

Example 2
A test of durability was conducted in the same manner as the evaluation method of Example 1 except that the tire B was tested.

Comparative Example 1
A durability test was conducted in the same manner as the evaluation method of Example 1 except that the heating step and the rim desorption step were not provided.

Comparative Example 2
A durability test was conducted in the same manner as the evaluation method of Example 2 except that the heating step and the rim desorption step were not provided.

Comparative Example 3
A durability test was conducted in the same manner as the evaluation method of Example 1 except that the rim desorption step was not provided.

[Example 3-6]
The durability test was conducted in the same manner as the evaluation method of Example 1 except that the heating period Ph was as shown in Table 2.

  In Table 1 and Table 2, “traveling time average” is indexed to the traveling time average of Comparative Example 1 as 100, and the other traveling time averages are indexed. The smaller this index, the shorter the running time average. The smaller this index, the better. In the "travel time variation", the variance of the other travel times was indexed, with the variance of the travel time of Comparative Example 3 being 100. The smaller the index, the smaller the variation. The smaller this index, the better. The “evaluation time” was set to 100 in the evaluation time of Comparative Example 1, and the other evaluation times were indexed. The smaller the index, the shorter the evaluation time. The smaller this index, the better.

  The damage form in Tables 1 and 2 was "PTL". In the evaluation methods of Example 1 and Example 2, the durability of the bead is evaluated in a short time as compared with the evaluation methods of Comparative Example 1 and Comparative Example 2. The evaluation method of the first embodiment has less variation in travel time than the evaluation method of the third comparative example. In the evaluation method of the example, the durability is evaluated with high accuracy and in a short time as compared with the evaluation method of the comparative example. As shown in Tables 1 and 2, the superiority of the present invention is apparent from the evaluation results.

  The evaluation method described above can be widely applied as a method of evaluating the durability of the bead of a pneumatic tire. This evaluation method is particularly suitable for evaluating the bead durability of heavy duty tires.

2 ... Test machine 4 ... Tire 6 ... Rim support 8 ... Drive drum 12 ... Temperature sensor 14 ... Control section

Claims (7)

A heating step in which the tire assembly in which the tire is incorporated into the rim is heated;
A rim detaching step in which the tire is removed from the rim after the heating step and is incorporated again into the rim or another rim;
And a running step in which the tire assembly after the rim attaching and detaching step is run.   The evaluation method according to claim 1, wherein in the heating step, the heating temperature Th of the tire assembly is set to the highest attainable temperature of the bead of the market tire.   The evaluation method according to claim 1 or 2, wherein in the heating step, the heating temperature Th of the tire assembly is 90 (° C) or more and 110 (° C) or less under dry heat.   The evaluation method according to any one of claims 1 to 3, wherein in the heating step, the heating period Ph of the tire assembly is from 1 day to 5 days under dry heat. In the heating step, the heating temperature Th of the tire assembly and the heating period Ph of the tire assembly, the inner diameter change amount Dc of the bead toe of the tire and the inner diameter change amount Dr of the bead toe of the market tire mm) is set to satisfy the unit equation,
The inner diameter change amount Dc is a value obtained by subtracting the inner diameter of the bead toe before the heating step from the inner diameter of the bead toe after the heating step, and the inner diameter change amount Dr is the bead toe of the tire whose service life has reached the market. The evaluation method according to any one of claims 1 to 4, which is a value obtained by subtracting the inner diameter of the unused bead toe from the inner diameter of.
(Dr-1) ≦ Dc ≦ (Dr + 1)   In the heating step, the heating temperature Th of the tire assembly and the heating period Ph of the tire assembly are set such that the inner diameter change amount Dc of the bead toe of the tire is 10 (mm) or more and 17 (mm) or less The evaluation method according to any one of claims 1 to 5, wherein It is equipped with the judgment process by which the pass / fail judgment of the said tire is carried out,
The longest running time at which the above-mentioned running process ends and a reference time shorter than the longest running time are set.
In the above determination step,
The evaluation method according to any one of claims 1 to 6, wherein the traveling time of the tire in the traveling step is compared with the reference time to make a pass determination.

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