GB/T 41321-2022 PDF English
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Test method for stiffness of self-supporting run-flat tyres
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GB/T 41321-2022: PDF in English (GBT 41321-2022) GB/T 41321-2022
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 83.160.10
CCS G 41
Test method for stiffness of self-supporting run-flat tyres
(ISO 19940:2017, Tyre stiffness index testing procedure for passenger car
extended mobility and run flat tyres, MOD)
ISSUED ON: MARCH 09, 2022
IMPLEMENTED ON: OCTOBER 01, 2022
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... 5
4 Test method ... 7
5 Test report ... 15
Test method for stiffness of self-supporting run-flat tyres
1 Scope
This document specifies the test method (including measurement test equipment and its
accuracy requirements, test conditions and test procedures) and test report for stiffness
of self-supporting run-flat tyres.
This document applies to the measurement of the stiffness of self-supporting run-flat
passenger car radial tyres.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this
document and are indispensable for its application. For dated references, only the
version corresponding to that date is applicable to this document; for undated references,
the latest version (including all amendments) is applicable to this document.
GB/T 2978, Size designation, dimensions, inflation pressure and load capacity for
passenger car tyres
GB/T 6326, Tyre terms and definitions (GB/T 6326-2014, ISO 4223-1:2002, NEQ)
GB/T 30196, Self-supporting run flat tyres (GB/T 30196-2022, ISO 16992:2018,
MOD)
3 Terms and definitions
Terms and definitions determined by GB/T 6326 and GB/T 30196, as well as the
following ones, are applicable to this document.
3.1
Reference inflation pressure
pref
Inflation pressure to be used as a first step in test conditions.
Note: in kilopascals (kPa).
3.2
Test inflation pressure
pi
Inflation pressure at the step “i”.
Note: in kilopascals (kPa).
3.3
Vertical stiffness
KZ
Tyre stiffness measured under vertical force input in inflated conditions.
Note: in Newtons per millimeter (N/mm).
3.4
Structural stiffness
Kstr
Tyre vertical stiffness measured in zero i.p. running mode.
Note: Structural stiffness is a function of the tyre’s construction and technological
content, in Newtons per millimeter (N/mm).
3.5
Air stiffness
Kair
A tyre characteristic, which is calculated as the difference between tyre vertical stiffness
(inflated) and tyre structural stiffness (uninflated).
Note: Air stiffness is a function of the air volume and the inflation pressure of the tyre
itself, in Newtons per millimeter (N/mm).
3.6
Deflection
SZ
Vertical displacement of the plate in the Z direction.
Note: in millimeters (mm).
4 Test method
4.1 General
Self-supporting run-flat tyres shall comply with the requirements of GB/T 30196.
4.2 Inflated tyre - Vertical stiffness measurement
4.2.1 Preparation of tyres
The inflation pressure is 250 kPa for the standard load tyres, and 290 kPa for the
reinforced load tyres. Fix the tyre on the test rim as specified in 4.2.3, and store for at
least 3 h at (25±3) °C. The deviation for the inflation pressure shall be ±3 kPa.
4.2.2 Tyre measurement positions
Take 3 equally distributed positions on the circumference of the tyre for measurement.
-- The reference position, which can be freely chosen, needs to be in contact with the
bearing plate. The splices, if visible, shall be avoided.
-- The other two positions shall be equally distributed around the tyre’s
circumference: distance between measurement positions approximately 120°.
4.2.3 Test rims
The test rims shall have humps (flat or round) on both rim sides, where the width shall
be in accordance with GB/T 2978. Stiff alloy or heavy duty rims shall be used as test
rims.
4.2.4 Test equipment basic requirements
4.2.4.1 The test equipment shall be able to apply a corresponding load between the tyre
and the bearing plate; the bearing plate dimensions shall be larger than the tyre footprint,
and can realize relative movement between the two (tyre towards bearing plate or
bearing plate towards tyre).
4.2.4.2 The rotational axis of the test tyre shall be parallel to the bearing plate, and the
relative movement between the two shall be as such to be able to keep the parallelism;
the maximum movement speed shall be 1 mm/s, and the acquisition rate shall be at least
5 data points for each millimetre of displacement.
4.2.5 Test equipment set-up
4.2.5.1 Before the test, the load cells shall start the data acquisition at 100 N.
4.2.5.2 At least the following data shall be recorded:
-- loading force (FZ) (N), accuracy ±0.5% of maximum load cell capacity, but in any
case, maximum 100 N;
-- absolute position (z) (mm) accuracy ±0.5 mm.
One vertical load value (FZ) shall correspond to only one absolute position value (z)
and vice versa.
4.2.5.3. The ambient temperature at the test equipment shall be (25±3) °C.
4.2.5.4 The total number of acquired data points shall be in the range of 100 ~ 1 000
per inflation pressure step (refer to Table 1). The surface of the bearing plate in contact
with the tyre during the measurement shall be smooth steel.
4.2.6 Maximum test load
The maximum test load under the tyre reference inflation pressure (pref) is 150% of the
load capacity corresponding to the load index value.
4.2.7 Test procedure
4.2.7.1 Mount the test tyre on the test equipment.
4.2.7.2 The initial distance between the test tyre and the bearing plate shall be at least
10 mm, measured as vertical distance between the lowest tyre point and the bearing
plate. To set the starting point for data acquisition, the inflated tyre is loaded with a light
load (FZ ≤ 100 N) to determine the contact point between the tyre and the bearing plate.
From this point, the tyre is moved back by at least 10 mm. This last position is the
starting point (0,0) to be used for all of the next inflation pressure steps.
4.2.7.3 Start the data recording.
4.2.7.4 Start loading the tyre using a constant loading speed of maximum 1 mm/s.
4.2.7.5 Inflation pressure step 1 is stopped at the maximum load (150% loading capacity
corresponding to load index), where the maximum deflection (SZmax) is recorded and
set as stopping criterion for the following inflation pressure steps.
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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