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GB/T 521-2023 English PDF (GBT521-2023)

GB/T 521-2023 English PDF (GBT521-2023)

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GB/T 521-2023: Test methods for measuring peripheral dimensions of tyres

This document describes the measurement methods for peripheral dimensions of pneumatic tyres (cover tyre, inner tube and pad belt), including measurement tools and their accuracy requirements, measurement conditions, measurement methods, data calculation and processing, and test reports. This document is applicable to passenger car tyres, truck tyres, agricultural tyres, engineering machinery tyres, industrial vehicle pneumatic tyres, motorcycle tyres, electric bicycle tyres and cycle tyres.
GB/T 521-2023
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 83.160.01
CCS G 41
Replacing GB/T 521-2012
Test methods for measuring peripheral dimensions of tyres
ISSUED ON: MARCH 17, 2023
IMPLEMENTED ON: OCTOBER 01, 2023
Issued by: State Administration for Market Regulation;
Standardization Administration of the People's Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Terms and definitions ... 6
4 Measurement tools and their accuracy requirements ... 6
5 Measurement conditions ... 6
6 Measurement methods ... 7
7 Data calculation and processing ... 10
8 Test report ... 11
Test methods for measuring peripheral dimensions of tyres
1 Scope
This document describes the measurement methods for peripheral dimensions of pneumatic tyres (cover tyre, inner tube and pad belt), including measurement tools and their accuracy requirements, measurement conditions, measurement methods, data calculation and processing, and test reports.
This document is applicable to passenger car tyres, truck tyres, agricultural tyres, engineering machinery tyres, industrial vehicle pneumatic tyres, motorcycle tyres, electric bicycle tyres and cycle 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 2977, Size designation, dimensions, inflation pressure and load capacity for truck tyres
GB/T 2978, Size designation, dimensions, inflation pressure and load capacity for passenger car tyres
GB/T 2979, Size designation, dimensions, inflation pressure and load capacity for agricultural tyres
GB/T 2980, Size designation, dimensions, inflation pressure and load capacity for earth-mover tyres
GB/T 2982, Designation, dimensions, inflation pressure and load capacity of pneumatic tyres for industrial vehicles
GB/T 2983, Series of motorcycle tyres
GB/T 6326, Tyre terms and definitions
GB/T 7377, Series of cycle tyres
GB/T 8170, Rules of rounding off for numerical values and expression and judgement of limiting values
GB/T 31548, Series of electric bicycle tyres
3 Terms and definitions
For the purposes of this document, the terms and definitions defined in GB/T 6326 apply.
4 Measurement tools and their accuracy requirements
4.1 Tyre pressure gauge:
- ??5 kPa; the measured air pressure is 500 kPa and below;
- ??10 kPa; the measured air pressure is above 500 kPa.
4.2 Steel ruler and metal tape measure (without curvature): ??1 mm.
4.3 Vernier caliper: ??0.1 mm.
4.4 Pattern depth gauge: ??0.02 mm.
4.5 Thickness gauge: ??0.01 mm.
4.6 Calipers.
4.7 Non-contact measuring instruments (such as laser measuring instruments): ??0.02 mm.
5 Measurement conditions
5.1 After the tyre is vulcanized, it shall be parked at room temperature for at least 24 h. Before inflating, it shall be parked at a temperature of 18??? ~ 36??? for at least 3 h. If necessary, clean the measurement position on the tyre surface before measurement. Trim vent beard and molding bead.
5.2 Tubeless tyres shall be mounted on rims for tubeless tyre measurements. Inflate according to 5.3. In order to make the tyre bead and rim fit in place, the inflation pressure can be increased appropriately under the premise of ensuring safety. After the bead is on and in place, adjust to the specified air pressure. Tyres with inner tubes (including cover tyres, inner tubes, and pad belts if required) shall be installed on the rims for measuring tyres with inner tubes. Inflate according to 5.3.
5.3 Inflate the tyre to the inflation pressure specified in Table 1.
Keys:
a - pattern depth gauge.
Figure 2 -- Schematic diagram of measuring tyre groove depth
6.4 Tread wear mark height
At the parts corresponding to at least 4 tread wear marks, measure the groove depth of each point and the height of the tread wear marks at each corresponding point from the tread (measure at least 3 places for motorcycle tyres and electric bicycle tyres). When measuring with a pattern depth gauge, the pattern depth gauge shall be kept perpendicular to the bottom of the pattern groove. When measuring the height of the tread wear mark from the tread, the pattern depth gauge shall be kept perpendicular to the upper plane of the tread wear mark and aligned with the middle position of the wear mark. When measuring with a non-contact measuring instrument, the measuring instrument shall be kept level with the groove and aligned with the middle position of the wear mark.
6.5 Pad belt thickness
Use a thickness gauge to measure the thickness of the middle part of the pad belt and the place less than or equal to 1mm from the edge of the pad belt. The thickened part of the valve hole shall be avoided. Measure 4 points on the four equal parts of the circumference of the pad belt, respectively.
6.6 Flattened width of the pad belt
After flattening the inner tube contact surface of the pad belt outward, use a steel ruler to measure its width. Measure about 4 points in quarters.
6.7 Outer circumference of inner tube
Let the inner tube stand for 2 h after exhausting the air. After placing it on a flat surface and folding it into a semicircle, use a tape measure to measure its outer half circumference. The resulting value is multiplied by 2, which shall be the outer circumference of the inner tube.
6.8 Flat-folded section width of inner tube
Flatten the cross section with a steel ruler. Measure the width at four quarters along the circumference of the inner tube.
7 Data calculation and processing
7.1 Outside diameter of tyre
The outer diameter of the tyre is calculated according to formula (1):
Where,
D - outer diameter of the tyre, in millimeters (mm);
L - outer circumference of the tyre, in millimeters (mm);
?€ - circumference ratio, taking 3.1416.
The data of the outer diameter of the tyre shall be rounded to an integer according to GB/T 8170.
7.2 Overall tyre width, section width, tyre groove depth, pad belt thickness, flattened width of pad belt
The overall width of the tyre is the maximum value of each measuring point. The arithmetic mean value of each measurement point is taken as the width of the section and the flattened width of the pad belt. The unit is millimeters. The above parameters of electric bicycle tyres and cycle tyres are rounded to one decimal place according to GB/T 8170. Others are rounded to integers according to GB/T 8170.
The arithmetic mean value of each measurement point is taken as the tyre groove depth and pad belt thickness. The unit is millimeters. Round off to one decimal place according to GB/T 8170.
7.3 Height of tread wear marks
The height of the tread wear mark is calculated according to formula (2): Where,

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