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This standard is developed in accordance with the rules given in GB/T 1.1-2009.
This standard was proposed by the China Petroleum and Chemical Industry Association.
This standard is under the jurisdiction of the National Technical Committee on Tyres and Rims of Standardization Administration of China (SAC/TC 19).
Drafting organizations of this standard: Triangle Tyre Co., Ltd., Guizhou Tyre Co., Ltd., Shandong Linglong Tire Co., Ltd., Double Coin Tyre Group Ltd., zc rubber Group Co., Ltd., Sailun Group Co., Ltd., Guangzhou Vanlead Group Co,. Ltd., Beijing Research & Design Institute of Rubber Industry, AEOLUS Tyre Co., Ltd., Double Star Group Co., Ltd., Qingdao Sentury Tire Co., Ltd., Giti Radial Tire (Anhui) Co., Ltd., Qingdao Zhijian Inspection Co., Ltd., Dalian Goodyear Tyre Co., Ltd., Bridgestone (China) Investment Co., Ltd., Continental Tires (China) Co., Ltd., Michelin (China) Investment Co., Ltd., Heilongjiang Red Valley Automotive Test Co., Ltd., Shanghai General Motors Wuling (SGMW), Shantou Haoda Tyre Test Equipment Co., Ltd., Zhejiang Cotan Tyre Co., Ltd. and Guangdong Matelong Automobile Technology Co., Ltd.
Chief drafters of this standard: Wang Yan, Meng Ying, Hu Long, Chen Shaomei, Xie Hui, Sun Wenguang, Li Zhengang, Liang Zhejia, Xu Lihong, Mou Shouyong, Wang Kexian, Li Zhao, Wang Xiumei, Liu Jingjing, Zhang Weiguo, Yin Qingye, Fu Guangping, Ma Zhong, Lu Yi, Zhao Xinhong, Jia Yonghui, Chen Xun, Li Weisheng and Qiu Yuqiang.
Test method for snow grip performance of truck & bus tyres
1 Scope
This standard specifies the method for measuring the snow grip performance of truck & bus tyres. To reduce the measurement deviation, this standard adopts the test method of comparing with standard reference test tyre.
It is applicable to the truck & bus tyres.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 6326 Tyre terms and definitions
3 Terms and definitions
For the purposes of this standard, the terms and definitions established in GB/T 6326 and the following ones apply.
3.1
candidate tyre
tyre that is evaluated by testing
3.2
standard reference test tyre; SRTT
a set of special candidate tyres that are used as a benchmark in an evaluation system These tyres usually have carefully controlled design features to minimize variation and they are produced, controlled and stored according to the relevant standards.
3.3
control tyre
tyre which is used to indirectly obtain the comparison result between candidate tyre and standard reference test tyre by comparing with the candidate tyre and then the standard reference test tyre when the candidate tyre and the standard reference test tyre cannot be directly compared on the same vehicle
3.4
braking test
specified amount of anti-blocking brake system (ABS) braking carried out repeatedly on the same tyre in a short time
3.5
mean fully developed deceleration; mfdd
mean deceleration calculated according to the measuring distance recorded when the vehicle slows down between two specified speeds
3.6
snow grip index; SG
ratio of the snow grip performance between the candidate tyre and the standard reference test tyre
3.7
acceleration test
specified amount of traction controlled acceleration test carried out repeatedly on the same tyre in a short time
3.8
acceleration force
acting force generated by applying acceleration moment, in Newtons
3.9
acceleration force coefficient; AFC
ratio of acceleration force to vertical load
3.10
average acceleration; AA
average acceleration calculated according to the measuring distance recorded when the vehicle accelerates between two specified speeds
4 Test methods
4.1 Tiny and light truck & bus tyres with single tyre load index less than or equal to 121 and speed level of N or above.
4.1.1 Principle
For the tiny and light truck & bus tyres with single tyre load index less than or equal to 121 and speed level of N or above, their snow grip performance is tested by braking method.
This test method is to test the deceleration performance of the tyre of a test vehicle equipped with ABS (anti-blocking brake system) during the braking process with an instrument. The test vehicle runs along a straight line at the initial speed during the test, and then its emergency braking is used, leading to the ABS action of the four wheels and the stable deceleration. The average deceleration of the vehicle from 25km/h to 10km/h is then calculated.
4.1.2 Test conditions
4.1.2.1 Road conditions
4.1.2.1.1 The snow road surface for testing is flat and even with the length above 500m, width above 5m and slope no greater than 2%.
4.1.2.1.2 The snow-piled road shall have a layer of at least 3cm-thick hard and compacted snow as the bottom layer and an about 2cm-thick compacted snow on the surface.
4.1.2.1.3 As for the snow compression index, ten measuring points shall be selected uniformly on the whole test road to calculate their average, and the maximum value does not differ from the minimum value by 8. The average of the snow compression index measured with snow hardness tester (CTI, see Annex A) is between 75 and 85.
4.1.2.2 Climate conditions
4.1.2.2.1 The ambient temperature measured at about 1m above the ground is between -21℃ and -7℃.
4.1.2.2.2 The snow temperature measured at about 1cm deep of the snow-piled road shall be between -21℃ and -9℃.
4.1.2.2.3 The temperature variation in the test process shall not exceed 10℃.
4.1.2.2.4 Direct sunlight or greatly changed sunlight or humidity shall be avoided during the test and the wind speed should not exceed 5m/s.
4.1.2.3 Test vehicle conditions
4.1.2.3.1 The test vehicle equipped with ABS system and applicable to both the candidate tyre and the standard reference test tyre are selected.
4.1.2.3.2 The test vehicle shall be equipped with a calibrated sensor for winter measurements, and the speed and distance data acquisition system shall be capable of storing the measurement results. The accuracy of the sensor and the system shall be such that the relative uncertainty of the measured or calculated mean fully developed deceleration is less than 1%.
4.1.3 Test and measuring instruments
4.1.3.1 The test and measuring instruments shall be insensitive to vibration, deceleration and changes of ambient temperature. All exposed parts shall be able to withstand 100% relative humidity, dust, shock, vibration and other unfavorable factors.
4.1.3.2 The speed of the test vehicle is measured with non-contact speed measuring instruments such as the fifth-wheel instrument or the global positioning system (GPS). In the ambient temperature of -21℃ to -7℃, the allowable error is:
a) vehicle speed measurement: ±1% or ±0.5km/h, whichever is larger;
b) distance measurement: ±0.1m.
4.1.3.3 During the test, the actual vehicle speed measured with the measuring instrument or the difference between the actual vehicle speed and the standard vehicle speed shall be displayed in the vehicle so that the driver can adjust the vehicle speed.
4.1.3.4 The accuracy of the air pressure gauge is ± 5kPa.
4.1.4 Candidate tyre
4.1.4.1 The 225/75R16LT 116/114 S standard reference test tyre shall be selected and shall meet the requirements of relevant domestic group standards
4.1.4.2 The candidate tyres shall be produced in the same batch and kept in the same environment. The glue burr and flashing of the tread as well as any foreign object shall be removed. Before the test, the tyre surface in contact with snow shall be cleaned
4.1.4.3 The candidate tyre shall run for 100km on the dry paved road before being tested.
4.1.4.4 The candidate tyres shall be assembled near the test site and shall be mounted on the rims used by the test vehicle by conventional mounting methods. Appropriate amount of lubricant can be used for ease of installation. All assembled tyres to be tested shall be placed under the same outdoor environment for at least 2h, and then the tyre inflation pressure shall be adjusted to the specified test value.
4.1.4.5 The vehicle load shall be such that the load applied to the tyre is between 60% and 100% of the load corresponding to the tyre load index. The tyre loads on the same axle differ by no more than 10%. The inflation pressure of the candidate tyre is the air pressure calculated based on the actual load. If the vehicle vertical load is less than 75% of the maximum load capacity of the tyre, the test air pressure is calculated according to equation (1):
pt=pr(0.75)1.25=0.7pr (1)
where,
pt——the test pressure;
pr——the inflation pressure corresponding to the maximum load capacity.
If the vehicle vertical load is not less than 75% of the maximum load capacity of the tyre, the test air pressure is calculated according to equation (2):
(2)
where,
pt——the test pressure;
pr——the inflation pressure corresponding to the maximum load capacity;
Qt——the actual static load of the tyre;
Qr——the maximum load marked on the tyre side.
4.1.5 Test procedures
4.1.5.1 Prepare the measuring instrument according to the requirements of 4.1.3.
4.1.5.2 Measure the ambient temperature and the snow road temperature with a temperature measuring device, the snow surface hardness with a CTI snow hardness tester and the wind speed.
4.1.5.3 First install a set of standard reference test tyres on the test vehicle, and run the vehicle along a straight line at a speed of 28km/h or above.
4.1.5.4 When the vehicle reaches the measurement area, shift to neutral gear and then suddenly apply a stable force to the brake pedal to make the ABS system of all the wheels of the vehicle act and decelerate the vehicle stably. This applied force shall be maintained until the vehicle is decelerated to less than 8km/h. Record the test speed and test distance automatically. If the test conditions do not meet the requirements, revoke all test data completely and carry out the test again.
4.1.5.5 Discard the first two test data of each test. Each set of standard reference test tyres shall be subjected to at least 6 effective tests and then the candidate tyres are subjected to at least 6 effective tests as well.
4.1.5.6 After at most two sets of candidate tyre tests, the standard reference test tyres, such as: R1, T1, T2, R2, T3, T4 and R3, need to be tested. Here, R stands for standard reference test tyre and T for candidate tyre.
4.1.5.7 Carry out the contrast test between the candidate tyre and the standard reference test tyre repeatedly in two different working days, and take the average of the two test results as the test result.
4.1.5.8 The areas where the ABS braking is fully applied shall not be overlapped, and when a new set of tyres is tested, avoid braking on the previously detected tyre tracks. When the areas where the ABS braking is fully applied are inevitably overlapped, retreat the test site pavement. The test running pavement of the candidate tyre shall have the same slope and compaction characteristics as that of the standard reference test tyre so as to ensure that the comparison between the candidate tyre and the standard reference test tyre is carried out under the same test road conditions.
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Test methods
5 Test report
Annex A (Normative) Snow hardness tester
