GB/T 521-2023Test methods for measuring peripheral dimensions of tyres (English PDF)

Foreword

This document was drafted in accordance with the rules given in GB/T 1.1-2020 "Directives for standardization - Part 1: Rules for the structure and drafting of standardizing documents".

This document replaces GB/T 521-2012 "Test method of measuring peripheral dimensions for tyres". Compared with GB/T 521-2012, in addition to the structural adjustments and editorial changes, the main technical changes in this document are as follows.

- Add "Electric bicycle tyres and rickshaw tyres" in the scope of application (see Chapter 1 of this Edition);

- Change the accuracy requirements for the tyre pressure gauge (see 4.1 of this Edition; 4.1 of Edition 2012);

- Add "non-contact measuring instruments" and related requirements (see 4.7 of this Edition);

- Add specific provisions on measuring inflation pressure (see Table 1 of this Edition);

- Add measurement method for "overall tyre width" (see 6.2.1 of this Edition);

- Change the provisions on the number of measurement points for "section width, groove depth, tread wear mark height" (see 6.2~6.4 of this Edition; 6.2~6.4 of Edition 2012);

- Change the value of "pi" from "3.14" to "3.1416" (see 7.1 of this Edition; 7.1 of Edition 2012).

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

4.2 Steel ruler and metal tape measure (without curvature). ±1 mm.

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°C ~ 36°C 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.

5.3 Inflate the tyre to the inflation pressure specified in Table 1.

5.4 After the tyre is inflated to the specified inflation pressure, park it at a temperature of 18°C~36°C for at least 24 h.

6 Measurement methods

7 Data calculation and processing

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 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.

8 Test report

The test report shall include the following.

a) Test tyre manufacturer name, trademark, specification, production number;

b) Tyre load index or load capacity or rating, measured air pressure;

c) Tyre outer circumference, outer diameter, overall width or section width;

d) Depth of tyre grooves, height of tread wear marks;

e) Thickness of pad belt, flattened width of pad belt;

f) Outer circumference of inner tube, flat folded section width; […]