PNEUMATIC TIRE

Abstract

Provided is a pneumatic tire for which rolling resistance at high speed running is sufficiently reduced and durability is sufficiently improved. The pneumatic tire has a side portion, a thickness S (mm) of a rubber layer radially outside a carcass on the side portion at the maximum tire width position is 3 mm or less, the loss tangent of the rubber layer measured under the conditions of 70° C., a frequency of 10 Hz, an initial distortion of 5%, and a dynamic distortion rate of 1% is 0.15 or less, and when the cross-sectional width of the tire is Wt (mm) and the outer diameter is Dt (mm) when installed on a regular rim and the internal pressure is 250 kPa, the volume of the space occupied by the tire is the virtual volume V (mm.sup.3), the following (formula 1) and (formula 2) are satisfied.

1700≤(Dt.sup.2×π/4)/Wt≤2827.4  (formula 1)

[(V+1.5×10.sup.7)/Wt]≤2.88×10.sup.5  (formula 2)

Claims

1. A pneumatic tire having a side portion, wherein the thickness S (mm) of the rubber layer radially outside the carcass of the side portion at the maximum width position of the tire is 3 mm or less; the loss tangent (70° C. tan δ) of the rubber layer is 0.15 or less measured under the conditions of 70° C., frequency of 10 Hz, initial strain of 5%, and dynamic strain rate of 1%; and when the cross-sectional width of the tire is Wt (mm), the outer diameter is Dt (mm), and the volume of the space occupied by the tire is the virtual volume V (mm.sup.3), when the tire is installed on a standardized rim and the internal pressure is 250 kPa, the tire satisfies following (formula 1) and (formula 2):
1700≤(Dt.sup.2×π/4)/Wt≤2827.4  (formula 1)
[(V+1.5×10.sup.7)/Wt]≤2.88×10.sup.5  (formula 2)

2. The pneumatic tire according to claim 1, wherein the following (formula 3) is satisfied.
[(V+2.0×10.sup.7)/Wt]≤2.88×10.sup.5  (formula 3)

3. The pneumatic tire according to claim 2, wherein the following (formula 4) is satisfied.
[(V+2.5×10.sup.7)/Wt]≤2.88×10.sup.5  (formula 4).

4. The pneumatic tire according to claim 1, wherein, when the outer diameter of the tire is Dt (mm) and the cross-sectional height of the tire is Ht (mm) when the tire is installed on a standardized rim and the internal pressure is 250 kPa, (Dt−2×Ht) is 470 (mm) or more.

5. The pneumatic tire according to claim 1, which has an aspect ratio of 40% or more.

6. The pneumatic tire according to claim 5, which has an aspect ratio of 45% or more.

7. The pneumatic tire according to claim 6, which has an aspect ratio of 47.5% or more.

8. The pneumatic tire according to claim 7, which has an aspect ratio of 50% or more.

9. The pneumatic tire according to claim 1, wherein the following (formula 5) is satisfied:
70° C. tan δ×(V/Wt)×S≤80000  (formula 5).

10. The pneumatic tire according to claim 9, wherein the following (formula 6) is satisfied:
70° C. tan δ×(V/Wt)×S≤60000  (formula 6).

11. The pneumatic tire according to claim 10, wherein the following (formula 7) is satisfied:
70° C. tan δ×(V/Wt)×S≤40000  (formula 7).

12. The pneumatic tire according to claim 11, wherein the following (formula 8) is satisfied:
70° C. tan δ×(V/Wt)×S≤35000  (formula 8).

13. The pneumatic tire according to claim 1, wherein Dt is less than 685 (mm), where Dt (mm) is the outer diameter of the tire when the tire is installed on a standardized rim and the internal pressure is 250 kPa.

14. The pneumatic tire according to claim 1, wherein the cross-sectional width Wt (mm) is less than 205 mm.

15. The pneumatic tire according to claim 14, wherein the cross-sectional width Wt (mm) is less than 200 mm.

16. The pneumatic tire according to claim 1, which is a pneumatic tire for a passenger car.

Description

EXAMPLES

[0171] Hereinafter, the present disclosure will be described in more specific with reference to Examples.

Experiment 1

[0172] In this experiment, 175 size tires were prepared and evaluated.

1. Manufacture of Rubber Compositions for Forming Side Portion

[0173] A rubber composition for forming side portion was produced.

(1) Compounding Material

[0174] First, each compounding material shown below was prepared.

(a) Rubber Component

[0175] (a-1) NR: TSR20 [0176] (a-2) BR-1: UBEPOL-BR150B manufactured by Ube Industries, Ltd. (cis content: 97% by mass) [0177] (a-3) BR-2: Nipol-BR1250H manufactured by Nippon Zeon Co., Ltd. (tin terminal modified BR, cis content: 40% by mass) [0178] (a-4) BR-3: UBEPOL VCR617 manufactured by Ube Industries, Ltd. (cis content: 98% by mass)

[0179] (b) Compounding Materials Other than Rubber Components [0180] (b-1) Carbon black: Show Black N550 manufactured by Cabot Japan Co., Ltd. (N.sub.2SA: 42m2/g) [0181] (b-2) Oil: Process X-140 manufactured by Japan Energy Co., Ltd. [0182] (b-3) Stearic acid: stearic acid “Tsubaki” manufactured by NOF Corporation [0183] (b-4) Zinc oxide: zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. [0184] (b-5) Wax: Sannok wax manufactured by Ouchi Shinko Chemical Industry Co., Ltd. [0185] (b-6) Antiaging agent-1: Nocrac 6C manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (N-phenyl-N′-(1,3-dimethylbutyl)-p-phenylenediamine) [0186] (b-7) Anti-aging agent-2: Antage RD manufactured by Kawaguchi Chemical Industry Co., Ltd. (2,2,4-trimethyl-1,2-dihydroquinoline) [0187] (b-8) Cross-linking agent and vulcanization accelerator

[0188] Sulfur: powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd.

[0189] Vulcanization accelerator: Nocceler NS manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (N-tert-butyl-2-benzothiazolylsulfenamide)

(2) Production of Rubber Composition for Forming Side Portion

[0190] In accordance with the formulation shown in Table 1 and Table 2, materials other than sulfur and the vulcanization accelerator were kneaded under the conditions of 150° C. for 5 minutes using a banbury mixer to obtain a kneaded product. Each compounding amount is a mass part.

[0191] Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and the mixture was kneaded at 80° C. for 5 minutes using an open roll to obtain a rubber composition for forming side portion.

2. Tire Manufacturing

[0192] Using the obtained rubber composition, a side member was formed to have a thickness S (mm) shown in Tables 1 and 2, and was bonded together with other tire members to form an unvulcanized tire, which is then press-vulcanized for 10 minutes under the condition of 170° C. to produce each test tire having a size of 175 type (Example 1-1 to Example 1-5 and Comparative Example 1-1 to Comparative Example 1-5).

3. Parameter Calculation

[0193] After that, the outer diameter Dt (mm), the cross-sectional width Wt (mm), the cross-sectional height Ht (mm), and the aspect ratio (%) of each test tire were obtained, and the virtual volume V (mm.sup.3) was calculated. At the same time, a rubber test piece for viscoelasticity measurement was produced by cutting out from the rubber layer of the side portion of each test tire in a length 20 mm×width 4 mm×thickness 1 mm so that the tire circumferential direction was the long side. For each rubber test piece, tan δ (70° C. tan δ) was measured under the conditions of 70° C., frequency 10 Hz, initial strain 5%, and dynamic strain 1% using an Eplexor series manufactured by GABO Co., Ltd. The results are shown in Tables 1 and 2.

[0194] Then, (Dt−2×Ht), (Dt.sup.2×π/4)/Wt, (V+1.5×10.sup.7)/Wt, (V+2.0×10.sup.7)/Wt, (V+2.5×10.sup.7)/Wt, and 70° C. tan δ×Wt were determined. The results are shown in Tables 1 and 2.

5. Performance Evaluation Test

(1) Evaluation of Rolling Resistance at High-Speed Running

[0195] Each test tire was installed on all wheels of the vehicle (domestic FF vehicle, displacement 2000 cc), filled with air so that the internal pressure became 250 kPa, and then driven on a dry road surface test course at a speed of 100 km/h. After making a 10 km lap, the accelerator was released, and the distance from when the accelerator was turned off until the vehicle stopped was measured as the rolling resistance at high-speed running.

[0196] Next, the result in Comparative Example 1-5 was set to as 100, and the results were indexed based on the following formula to relatively evaluate the rolling resistance at high-speed running. The larger the value, the longer the distance from when the accelerator is turned off until the vehicle stops and the smaller the rolling resistance in the steady state, and showing excellent fuel efficiency.

Rolling resistance=[(Result of test tire)/(Result of Comparative Example 1-5)]×100

(2) Evaluation of Durability Performance

[0197] After installing each test tire on all wheels of the vehicle (domestic FF vehicle, displacement 2000 cc) and filling it with air so that the internal pressure becomes 250 kPa, a driving 10 laps at a speed of 50 km/h, followed by climbing onto the unevenness provided on the road surface at a speed of 80 km/h was repeated on the test course on a dry road surface in an overloaded state. Thereafter, the lap was performed again at a speed of 50 km/h and then the speed was gradually increased to measure the speed at the time when the driver felt an abnormality.

[0198] Next, the result in Comparative Example 1-5 was set to as 100, and the durability performance was relatively evaluated by indexing based on the following formula. The larger the value, the better the durability.

Durability=[(Result of test tire)/(Result of Comparative Example 1-5)]×100

(3) Comprehensive Evaluation

[0199] The evaluation results of (1) and (2) above were totaled to obtain a comprehensive evaluation.

(4) Evaluation Result

[0200] The results of each evaluation are shown in Tables 1 and 2.

TABLE-US-00001 Example No. 1-1 1-2 1-3 1-4 1-5 SIZE 175/ 175/ 175/ 175/ 175/ 40R21 40R21 40R21 50R20 60R19 (Formulation) NR 40 40 40 40 40 BR 1 BR 2 30 30 30 30 30 BR 3 30 30 30 30 30 Carbon black 45 40 40 45 45 Oil 15 15 15 15 15 Stearic acid 3 3 3 3 3 Zinc oxide 4.5 4.5 4.5 4.5 4.5 Wax 2 2 2 2 2 Anti-aging 4.5 4.5 4.5 4.5 4.5 agent-1 Anti-aging 2 2 2 2 2 agent-2 Sulfur 2 2 2 2 2 Vulcanization 1 1.5 1.5 1 1 accelerator (Parameter) 70° C. tanδ 0.11 0.07 0.07 0.11 0.11 S (mm) 3 3 1.5 3 3 Dt (mm) 674 673 672 684 692 V (mm.sup.3) 23672177 23206160 23136067 30111710 34196412 Wt (mm) 176 175 177 181 178 Ht(mm) 71 70 69 89 104 Dt − 2 × 532 533 534 506 484 Ht(mm) (Dt.sup.2 × π/4)/Wt 2027 2033 2004 2030 2113 (V + 1.5 × 219728 218321 215458 249236 276384 10.sup.7)/Wt (V + 2.0 × 248137 246892 243707 276860 304474 10.sup.7)/Wt (V + 2.5 × 276546 275464 271955 304485 332564 10.sup.7)/Wt Aspect ratio 40 40 39 49 58 (%) 70° C. tanδ × 44385 27847 13725 54900 63398 V/Wt × S (Evaluation result) Rolling 116 120 132 112 110 resistance at high-speed running Durability 124 128 136 120 112 Comprehensive 240 248 268 232 222 evaluation

TABLE-US-00002 TABLE 2 Comparative example No. 1-1 1-2 1-3 1-4 1-5 SIZE 175/ 175/ 175/ 175/ 175/ 80R14 60R19 80R14 80R14 80R14 (Formulation) NR 40 40 40 40 40 BR 1 60 60 60 BR 2 30 30 BR 3 30 30 Carbon black 60 60 60 45 40 Oil 15 15 15 15 15 Stearic acid 3 3 3 3 3 Zinc oxide 4.5 4.5 4.5 4.5 4.5 Wax 2 2 2 2 2 Anti-aging 4.5 4.5 4.5 4.5 4.5 agent-1 Anti-aging 2 2 2 2 2 agent-2 Sulfur 2 2 2 2 2 Vulcanization 1 1 1 1 1.5 accelerator (Parameter) 70° C. tanδ 0.2 0.2 0.2 0.11 0.07 S (mm) 5 5 3 5 3 Dt (mm) 636 693 635 637 636 V (mm.sup.3) 38414424 34599284 38317377 38669035 38414424 Wt (mm) 177 177 176 176 177 Ht(mm) 139 106 140 141 139 Dt − 2 × 358 481 355 355 358 Ht(mm) (Dt.sup.2 × π/4)/Wt 1795 2131 1799 1811 1795 (V + 1.5 × 301776 280222 302940 304938 301776 10.sup.7)/Wt (V + 2.0 × 330025 308471 331349 333347 330025 10.sup.7)/Wt (V + 2.5 × 358274 336719 359758 361756 358274 10.sup.7)/Wt Aspect ratio 79 60 80 80 79 (%) 70° C. tanδ × 217031 195476 130627 120841 45576 V/Wt × S (Evaluation result) Rolling 94 98 94 96 100 resistance at high speed running Durability 90 96 96 92 100 Comprehensive 184 194 190 188 200 evaluation

Experiment 2

[0201] In this experiment, 195 size tires were prepared and evaluated.

[0202] After producing the test tires of Examples 2-1 to 2-5 and Comparative Examples 2-1 to 2-5 shown in Tables 3 and 4 in the same manner as in Experiment 1, each parameter was calculated by performing the same procedure. Then, in the same manner, a performance evaluation test was conducted and evaluated. In this experiment, the result in Comparative Example 2-5 was set as 100 for evaluation. The results of each evaluation are shown in Tables 3 and 4.

TABLE-US-00003 TABLE 3 Example No. 2-1 2-2 2-3 2-4 2-5 SIZE 195/ 195/ 195/ 195/ 195/ 40R20 40R20 40R20 50R19 60R18 (Formulation) NR 40 40 40 40 40 BR 1 BR 2 30 30 30 30 30 BR 3 30 30 30 30 30 Carbon black 45 40 40 45 45 Oil 15 15 15 15 15 Stearic acid 3 3 3 3 3 Zinc oxide 4.5 4.5 4.5 4.5 4.5 Wax 2 2 2 2 2 Anti-aging 4.5 4.5 4.5 4.5 4.5 agent-1 Anti-aging 2 2 2 2 2 agent-2 Sulfur 2 2 2 2 2 Vulcanization 1 1.5 1.5 1 1 accelerator (Parameter) 70° C. tanδ 0.11 0.07 0.07 0.11 0.11 S (mm) 3 3 1.5 3 3 Dt (mm) 665 663 664 680 691 V (mm.sup.3) 29087378 28526824 28431992 35417448 42618582 Wt (mm) 200 199 198 196 202 Ht(mm) 79 78 78 99 117 Dt − 2 × 507 507 508 482 457 Ht(mm) (Dt.sup.2 × π/4)/Wt 1737 1735 1749 1853 1856 (V + 1.5 × 220437 218728 219353 257232 285241 10.sup.7)/Wt (V + 2.0 × 245437 243853 244606 282742 309993 10.sup.7)/Wt (V + 2.5 × 270437 268979 269859 308252 334745 10.sup.7)/Wt Aspect ratio 40 39 39 51 58 (%) 70° C. tanδ × 47994 30104 15078 59631 69624 V/Wt × S (Evaluation result) Rolling 118 122 126 116 118 resistance at high-speed running Durability 126 132 134 118 110 Comprehensive 244 254 260 234 228 evaluation

TABLE-US-00004 TABLE 4 Comparative example No. 2-1 2-2 2-3 2-4 2-5 SIZE 195/ 195/ 195/ 195/ 195/ 65R17 40R20 65R17 65R17 65R17 (Formulation) NR 40 40 40 40 40 BR 1 60 60 60 BR 2 30 30 BR 3 30 30 Carbon black 60 60 60 45 40 Oil 15 15 15 15 15 Stearic acid 3 3 3 3 3 Zinc oxide 4.5 4.5 4.5 4.5 4.5 Wax 2 2 2 2 2 Anti-aging 4.5 4.5 4.5 4.5 4.5 agent-1 Anti-aging 2 2 2 2 2 agent-2 Sulfur 2 2 2 2 2 Vulcanization 1 1 1 1 1.5 accelerator (Parameter) 70° C. tanδ 0.2 0.2 0.2 0.11 0.07 S (mm) 5 5 3 5 3 Dt (mm) 686 664 686 685 687 V (mm.sup.3) 44829249 28719183 44877023 44971685 44957448 Wt (mm) 201 200 200 202 200 Ht(mm) 127 78 128 127 128 Dt − 2 × 432 508 430 431 431 Ht(mm) (Dt.sup.2 × π/4)/Wt 1839 1731 1848 1824 1853 (V + 1.5 × 297658 218596 299385 296890 299787 10.sup.7)/Wt (V + 2.0 × 322534 243596 324385 321642 324787 10.sup.7)/Wt (V + 2.5 × 347409 268596 349385 346394 349787 10.sup.7)/Wt Aspect ratio 63 39 64 63 64 (%) 70° C. tanδ × 223031 143596 134631 122448 47205 V/Wt × S (Evaluation result) Rolling 96 98 96 98 100 resistance at high speed running Durability 90 96 96 94 100 Comprehensive 186 194 192 192 200 evaluation

Experiment 3

[0203] In this experiment, 225 size tires were prepared and evaluated.

[0204] After producing the test tires of Examples 3-1 to 3-5 and Comparative Examples 3-1 to 3-5 shown in Tables 5 and 6 in the same manner as in Experiment 1, each parameter was calculated by performing the same procedure. Then, in the same manner, a performance evaluation test was conducted and evaluated. In this experiment, the result in Comparative Example 3-5 was set as 100 for evaluation. The results of each evaluation are shown in Tables 5 and 6.

TABLE-US-00005 TABLE 5 Example No. 3-1 3-2 3-3 3-4 3-5 SIZE 225/ 225/ 225/ 225/ 225/ 35R22 35R22 35R22 50R20 40R21 (Formulation) NR 40 40 40 40 40 BR 1 BR 2 30 30 30 30 30 BR 3 30 30 30 30 30 Carbon black 45 40 40 45 45 Oil 15 15 15 15 15 Stearic acid 3 3 3 3 3 Zinc oxide 4.5 4.5 4.5 4.5 4.5 Wax 2 2 2 2 2 Anti-aging 4.5 4.5 4.5 4.5 4.5 agent-1 Anti-aging 2 2 2 2 2 agent-2 Sulfur 2 2 2 2 2 Vulcanization 1 1.5 1.5 1 1 accelerator (Parameter) 70° C. tanδ 0.11 0.07 0.07 0.11 0.11 S (mm) 3 3 1.5 3 3 Dt (mm) 716 718 717 734 713 V (mm.sup.3) 36203610 37040131 35785417 50043281 40161995 Wt (mm) 229 231 226 227 228 Ht(mm) 79 80 79 113 90 Dt − 2 × 558 558 559 508 533 Ht(mm) (Dt.sup.2 × π/4)/Wt 1758 1753 1787 1864 1751 (V + 1.5 × 223597 225282 224714 286534 241939 10.sup.7)/Wt (V + 2.0 × 245431 246927 246838 308561 263868 10.sup.7)/Wt (V + 2.5 × 267265 268572 268962 330587 285798 10.sup.7)/Wt Aspect ratio 34 35 35 50 39 (%) 70° C. tanδ × 52171 33673 16626 72750 58129 V/Wt × S (Evaluation result) Rolling 108 116 126 110 114 resistance at high-speed running Durability 126 130 128 122 114 Comprehensive 234 246 254 232 228 evaluation

TABLE-US-00006 TABLE 6 Comparative example No. 3-1 3-2 3-3 3-4 3-5 SIZE 225/ 225/ 225/ 225/ 225/ 60R20 50R20 60R20 60R20 60R20 (Formulation) NR 40 40 40 40 40 BR 1 60 60 60 BR 2 30 30 BR 3 30 30 Carbon black 60 60 60 45 40 Oil 15 15 15 15 15 Stearic acid 3 3 3 3 3 Zinc oxide 4.5 4.5 4.5 4.5 4.5 Wax 2 2 2 2 2 Anti-aging 4.5 4.5 4.5 4.5 4.5 agent-1 Anti-aging 2 2 2 2 2 agent-2 Sulfur 2 2 2 2 2 Vulcanization 1 1 1 1 1.5 accelerator (Parameter) 70° C. tanδ 0.2 0.2 0.2 0.11 0.07 S (mm) 5 5 3 5 3 Dt (mm) 778 736 732 735 777 V (mm.sup.3) 62176957 51904024 50611309 51375765 62080258 Wt (mm) 228 233 232 231 228 Ht(mm) 135 114 112 114 135 Dt − 2 × 508 508 508 507 507 Ht(mm) (Dt.sup.2 × π/4)/Wt 2085 1826 1814 1837 2080 (V + 1.5 × 338495 287142 282807 287341 338071 10.sup.7)/Wt (V + 2.0 × 360425 308601 304359 308986 360001 10.sup.7)/Wt (V + 2.5 × 382355 330060 325911 330631 381931 10.sup.7)/Wt Aspect ratio 59 49 48 49 59 (%) 70° C. tanδ × 272706 222764 130891 122323 57179 V/Wt × S (Evaluation result) Rolling 96 98 96 94 100 resistance at high-speed running Durability 90 96 96 92 100 Comprehensive 186 194 192 186 200 evaluation

Summary of Experiments 1 to 3

[0205] From the results of Experiments 1 to 3 (Tables 1 to 6), for tires of any size, 175 size, 195 size, 225 size, it turns out that it is possible to provide a pneumatic tire in which the rolling resistance at high-speed running is sufficiently reduced and the durability is sufficiently improved, when the above (formula 1) and (formula 2) are satisfied.

[0206] Then, it turns out that, by satisfying each of the requirements specified in claim 2 and thereafter, it is possible to provide a tire with further improved rolling resistance and durability at high-speed running.

[0207] On the other hand, when either (formula 1) or (formula 2) is not satisfied, the rolling resistance at high-speed running cannot be sufficiently reduced, and the durability cannot be sufficiently improved.

Experiment 4

[0208] Next, three types of tires (Examples 4-1 to 4-3), in which the relationship between the virtual volume V and the cross-sectional width Wt did not differ significantly, were produced with the same formulation and evaluated in the same manner. Here, in addition to the evaluation of rolling resistance and durability during high-speed running, the ride comfort was also evaluated.

[0209] Specifically, each test tire was installed on all wheels of the vehicle (domestic FF vehicle, displacement 2000 cc), filled with air so that the internal pressure became 250 kPa, and then driven on a dry road surface test course. The driver sensory-tested the ride comfort on a 5-point scale when the vehicle has driven 10 km at a speed of 100 km/h. After summing up the evaluations by 20 drivers, the evaluation was indexed based on the following formula, with the total score in Example 4-3 being 100, and the riding comfort was relatively evaluated. A larger value indicates better riding comfort.

Ride comfort=[(Total evaluation score of test tire)/(Total evaluation score of Example 4-3)]×100

[0210] Then, as in Experiments 1 to 3, each evaluation result was totaled to obtain a comprehensive evaluation. Table 7 shows the results of each evaluation.

TABLE-US-00007 TABLE 7 Example No. 4-1 4-2 4-3 SIZE 175/55R18 195/50R19 225/45R20 (Formulation) NR 40 40 40 BR 1 BR 2 30 30 30 BR 3 30 30 30 Carbon black 45 45 45 Oil 15 15 15 Stearic acid 3 3 3 Zinc oxide 4.5 4.5 4.5 Wax 2 2 2 Anti-aging agent-1 4.5 4.5 4.5 Anti-aging agent-2 2 2 2 Sulfur 2 2 2 Vulcanization 1 1 1 accelerator (Parameter) 70° C. tanδ 0.11 0.11 0.11 S (mm) 1.5 1.5 1.5 Dt (mm) 649 679 710 V (mm.sup.3) 30354118 35954077 43478150 Wt (mm) 182 201 225 Ht(mm) 96 98 101 Dt − 2 × Ht(mm) 457 483 508 (Dt.sup.2 × π/4)/Wt 1818 1801 1760 (V + 1.5 × 10.sup.7)/Wt 249198 253503 259903 (V + 2.0 × 10.sup.7)/Wt 276671 278378 282125 (V + 2.5 × 10.sup.7)/Wt 304144 303254 304347 Aspect ratio (%) 53 49 45 70° C. tanδ × V/Wt × S 27519 29515 31884 (Evaluation result) Rolling resistance at 110 106 100 high-speed running Durability 100 104 106 Ride confort 110 106 100 Comprehensive 320 315 306 evaluation

[0211] Table 7 shows that, when there is no large difference in the relationship between the virtual volume V and the cross-sectional width Wt, the rolling resistance at high-speed running and durability are both improved, as the cross-sectional width Wt becomes smaller as from less than 205 mm to less than 200 mm, and as the aspect ratio increases. It was also found that the ride comfort was improved.

[0212] Although the present disclosure has been described above based on the embodiments, the present disclosure is not limited to the above embodiments. Various modifications can be made to the above embodiments within the same and equal range as the present disclosure.

[0213] The present disclosure (1) is; [0214] a pneumatic tire having a side portion, wherein [0215] the thickness S (mm) of the rubber layer radially outside the carcass of the side portion at the maximum width position of the tire is 3 mm or less; [0216] the loss tangent (70° C. tan δ) of the rubber layer is 0.15 or less measured under the conditions of 70° C., frequency of 10 Hz, initial strain of 5%, and dynamic strain rate of 1%; and [0217] when the cross-sectional width of the tire is Wt (mm), the outer diameter is Dt (mm), and the volume of the space occupied by the tire is the virtual volume V (mm.sup.3), when the tire is installed on a standardized rim and the internal pressure is 250 kPa, the tire satisfies following (formula 1) and (formula 2):

1700≤(Dt.sup.2×π/4)/Wt≤2827.4  (formula 1)

[(V+1.5×10.sup.7)/Wt]≤2.88×10.sup.5  (formula 2)

[0218] The present disclosure (2) is the pneumatic tire according to the present disclosure (1), wherein the following (formula 3) is satisfied.

[(V+2.0×10.sup.7)/Wt]≤2.88×10.sup.5  (formula 3)

[0219] The present disclosure (3) is the pneumatic tire according to the present disclosure (2), wherein the following (formula 4) is satisfied.

[(V+2.5×10.sup.7)/Wt]≤2.88×10.sup.5  (formula 4)

[0220] The present disclosure (4) is the pneumatic tire of any combination of the present disclosures (1) to (3), wherein, when the outer diameter of the tire is Dt (mm) and the cross-sectional height of the tire is Ht (mm) when the tire is installed on a standardized rim and the internal pressure is 250 kPa, (Dt−2×Ht) is 470 (mm) or more.

[0221] The present disclosure (5) is the pneumatic tire of any combination of the present disclosures (1) to (4), which has an aspect ratio of 40% or more.

[0222] The present disclosure (6) is the pneumatic tire according to the present disclosure (5), which has an aspect ratio of 45% or more.

[0223] The present disclosure (7) is the pneumatic tire according to the present disclosure (6), which has an aspect ratio of 47.5% or more.

[0224] The present disclosure (8) is the pneumatic tire according to the present disclosure (7), which has an aspect ratio of 50% or more.

[0225] The present disclosure (9) is the pneumatic tire of any combination of the present disclosures (1) to (8), wherein the following (formula 5) is satisfied:

70° C. tan δ×(V/Wt)×S≤80000  (formula 5)

[0226] The present disclosure (10) is the pneumatic tire according to the present disclosure (9), wherein the following (formula 6) is satisfied:

70° C. tan δ×(V/Wt)×S≤60000  (formula 6)

[0227] The present disclosure (11) is the pneumatic tire according to the present disclosure (10), wherein the following (formula 7) is satisfied:

70° C. tan δ×(V/Wt)×S≤40000  (formula 7)

[0228] The present disclosure (12) is the pneumatic tire according to the present disclosure (11), wherein the following (formula 8) is satisfied:

70° C. tan δ×(V/Wt)×S≤35000  (formula 8)

[0229] The present disclosure (13) is the pneumatic tire of any combination of the present disclosures (1) to (12), wherein Dt is less than 685 (mm), where Dt (mm) is the outer diameter of the tire when the tire is installed on a standardized rim and the internal pressure is 250 kPa.

[0230] The present disclosure (14) is the pneumatic tire of any combination of the present disclosures (1) to (13), wherein the cross-sectional width Wt (mm) is less than 205 mm.

[0231] The present disclosure (15) is the pneumatic tire according to the present disclosure (14), wherein the cross-sectional width Wt (mm) is less than 200 mm.

[0232] The present disclosure (16) is the pneumatic tire of any combination of the present disclosures (1) to (15), which is a pneumatic tire for a passenger car.