GB/T 33829-2017 PDF English
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Test method for snow grip performance of passenger car tyres
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GB/T 33829-2017: PDF in English (GBT 33829-2017) GB/T 33829-2017
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 83.160.10
G 41
Test method for snow grip performance
of passenger car tyres
ISSUED ON: MAY 31, 2017
IMPLEMENTED ON: APRIL 01, 2018
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Terms and definitions ... 4
4 Test method ... 5
5 Test report ... 12
Appendix A (Normative) Snow hardness tester ... 13
Test method for snow grip performance
of passenger car tyres
1 Scope
This Standard specifies the method for snow grip performance of passenger
car tyres. To reduce the measurement deviation, this Standard uses a test
method of comparison with standard tyres.
This standard applies to passenger car tyres.
2 Normative references
The following documents are indispensable for the application of this document.
For dated references, only the dated version applies to this document. For
undated references, the latest edition (including all amendments) applies to this
document.
GB/T 6326, Tyre terms and definitions
3 Terms and definitions
Terms and definitions determined by GB/T 6326 and the following ones are
applicable to this document.
3.1 Candidate tyre
The tyre that is measured through the test.
3.2 Standard reference test tyre; SRTT
Standard reference test tyre
A set of special candidate tyres that are used as a reference in the
measurement system. To minimize the variation, these tyres which have tightly
controlled design characteristics, are produced, controlled and stored according
to relevant standards.
3.3 Control tyre
The tyre that -- If the candidate tyre and the standard tyre cannot be directly
compared on the same vehicle, THEN, compare the tyre with the candidate tyre,
(CTI, see Appendix A) is 75 ~ 85.
4.2.2 Climatic conditions
The ambient temperature range which is measured at about 1 m above the
ground is -21°C ~ -7°C;
The snow temperature which is measured at a depth of about 1 cm from the
snowy road surface shall be -21°C ~ -9°C;
The temperature variation during the test shall not exceed 10°C.
During the test, large variation in direct sunlight and humidity shall be avoided;
the wind speed should not exceed 5 m/s.
4.2.3 Test vehicle conditions
4.2.3.1 Select an ABS-equipped test vehicle to which both the candidate tyre
and the standard tyre are applicable.
4.2.3.2 The test vehicle shall be equipped with a calibrated sensor suitable for
winter measurements. The speed and distance data acquisition system shall
be equipped with a function to store measurement results. The sensor and
system accuracy shall meet the requirement that the relative uncertainty of the
measured or calculated mean fully developed deceleration is less than 1%.
4.3 Test measurement instrument
4.3.1 Test measurement instruments shall be insensitive to vibration,
deceleration and ambient temperature changes. All the exposed parts shall be
able to withstand 100% relative humidity, dust, shock, vibration and other
unfavorable factors.
4.3.2 The speed of the test vehicle shall be measured by a non-contact speed
measurement instrument such as a five-wheeled instrument or a global
positioning system (GPS). In the range of ambient temperature of -21°C ~ -7°C,
the allowable error:
a) Vehicle speed measurement: ± 1% or ± 0.5 km/h, whichever is larger;
b) Distance measurement: ± 0.1 m.
4.3.3 During the test, the vehicle shall display the actual vehicle speed
measured by measurement-instrument OR the difference BETWEEN the actual
vehicle speed AND the standard vehicle speed, so that the driver can adjust the
vehicle speed.
4.3.4 The accuracy of the barometer shall be ± 5 kPa.
4.6.7 Calculation of snow grip index of the candidate tyre:
Calculate the snow grip index SG, which indicates the ratio of braking
performance of the candidate tyre to the standard tyre on the snowy road,
according to Formula (9):
A -- average of the average-deceleration of the candidate tyre, in meters per
square second (m/s2);
WA -- weighted-average of the average-deceleration of the standard tyre, in
meters per square second (m/s2).
4.7 Adopt control tyre to test the snow performance
4.7.1 Overview
If the candidate tyre and the standard tyre differ greatly on specifications, and
cannot be directly compared on the same vehicle, then, use candidate tyres to
perform comparison test respectively.
4.7.2 Principle
Use control tyres and two different test vehicles to perform comparison tests
with the candidate tyres respectively. One of the test vehicles is suitable for the
assembly of the standard tyre and the control tyre; the other is suitable for the
assembly of the candidate tyre and the control tyre. The former is used to
measure the standard tyre and the control tyre, and the latter is used to
measure the candidate tyre and the control tyre. The two vehicles shall be
tested on the same road surface; the surface temperature difference between
the two tests shall be within 5°C. Two test vehicles shall use the same set of
four control tyres which shall be mounted on the same position. The
environmental conditions shall be comparable; all tests shall be completed
within the same day.
Calculate the snow grip index SG of the candidate tyre relative to the standard
tyre according to Formula (10):
Where:
SG1 -- relative index of the control tyre and the standard tyre;
Appendix A
(Normative)
Snow hardness tester
A.1 Conditions of use
A.1.1 Snow compression and shear strength have a great influence on the tyre
traction performance. These parameters cannot be ignored. However, changes
of these two aspects can be quantified by vertical and horizontal compaction
tests. CTI snow hardness tester can measure and characterize snow surface
compaction.
A.1.2 The top of CTI snow hardness tester is a 1.6-mm-radius ball that looks
like a plumb (see Figure A.1), and the other end is a measuring rod. Including
the knurled nut at the measuring top, the entire instrument, in the laboratory,
shall be adjusted to a weight of 220 g ± 1g; the height of the measuring rod
shall be adjusted to 218.9 mm ± 0.25 mm.
A.1.3 When using, the ball and the measuring rod are freely dropped at a
predetermined height from the rail with the flange end to the tested surface, and
the kinetic energy is converted into vertical insertion and horizontal
compression. The insertion distance is directly represented by the number (50
~ 100) from the handheld-scale.
A.1.4 In order to ensure the consistency of the entire test-site, the range of
values which is measured from different areas of the test-site shall not exceed
8.
A.2 Instructions for use
A.2.1 When the CTI snow hardness tester is used on site, the instrument shall
be placed on the snow surface to ensure that the metal part of the instrument
has the same temperature as the snow surface. After each measurement, the
head of the measuring rod shall be wiped clean to ensure that no extra
snowflakes are inside the instrument. If other factors cause snowflakes inside
the instrument, the best way is melting the snowflakes instead of disassembling
the instrument. If the instrument needs to be disassembled, be sure to
remember clearly the location of all parts before disassembly.
A.2.2 The standard test method is as follows: drive the vehicle with normal tyres
on the front wheels over the test-site; then move the vehicle to expose the
previous tyre pressing-mark; place the instrument in the center of the tyre
pressing-mark; lift up the measuring rod; gently turn the instrument for 45° and
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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