هيئة التقييس لدول مجلس التعبون لدول الخليج العربية 
GCC STANDARDIZATION ORGANIZATION (GSO)  
 
 
 
 
 
مشزوع:  نهبئي  
 
 
 
GSO2/1/FDS/GSO 646 : 201 3 
 
 
إطارات السيارات متعددة الأغراض والشاحنات 
والحافلات والمقطورات الجزء الثاني : طرق الاختبار 
MULTI -PURPOSE VEHICLES, TRUCKS,  
BUSES AND TRAILERS TYRES  
PART 2: METHODS OF TEST  
 
 
 
 
 
 
 
 
 
إعذاد 
اللجنت الفنيت الفزعيت الخليجيت لقطبع مىاصفبث المزكببث والإطبراث 
 
 
هذه الىثيقت مشزوع لمىاصفت قيبسيت خليجيت تم تىسيعهب لإبذاء الزأي والملاحظبث بشأنهب، لذلك فإنهب 
عزضت للتغييز والتبذيل، ولا يجىس الزجىع إليهب كمىاصفت قيبسيت خليجيت إلا بعذ اعتمبدهب من مجلس 
إدارة الهيئت.   
 
تقديم
هيئة التقييس لدول مجمس التعاون لدول الخميج العربية هيئة إقميمية تضم في عضويتها الأجهزة الوطنية 
لممواصفات والمقاييس في دول الخميج العربية ، ومن مهام الهيئة إعداد المواصفات القياسية الخميجية 
بواسطة لجان فنية متخصصة .  
 
وقد قامت هيئة التقييس لدول مجمس التعاون لدول الخميج العربية ضمن برنامج عمل المجنة الفنية رقم 
2-1 "  لمجنة الفنية الخميجية لقطاع مواصفات المركبات والإطارات "  بتحديث المواصفة القياسية 
الخميجية رقم 646 / 1996م،" إطارات السيارات متعددة الأغراض والشاحنات والحافلات والمركبات 
التجارية والمقطورات الجزء الثاني : طرق الاختبار " .وقامت سمطنة عمان بإعداد مشروع هذه المواصفة .   
 
وقد اعتمدت هذه المواصفة كـ(مواصفة قياسية  / لائحة فنية ) خميجية في اجتماع مجمس إدارة الهيئة رقم  (           
) ، الذي عقد بتاريخ      /      /      هـ ، الموافق    /    /     م. عمى أن تُمغِي المواصفة رقم (    
/    ) وتَحل محمها.  
Foreword 
 
GCC Standardization Organization (GSO) is a regional Organization which 
consists of the National Standards Bodies  of GCC member States. One of GSO 
main functions is to issue Gulf Standards /Technical regulation s through 
specialized technical committees (TCs).  
 
GSO through the technical program of committee TC No . 2-1 "The Gulf 
technical Subcommittee for vehicles and tyres standards" has updated the GSO 
Standard No. : 646/1996  "multi -purpose vehicles, trucks, Buses and trailers 
tyres  Part 2: methods of test". The Draft Standard has been prepared by 
Sultanate of Oman.  
  
This standard has been approved as a Gulf (Standar d / Technical Regulation) by 
GSO Board of Directors  in its meeting No.(       ),held on      /    /            H ,     /     
/              G. The approved standard will replace and supersede the GSO 
standard No. (       /      ).    GSO STANDARD  GSO   646    / 
 
1 
  
MULTI -PURPOSE VEHIC LES, TRUCKS,  
BUSES AND TRAILERS TYRES  
PART 2: METHODS OF TEST  
 
 
1. SCOPE AND FIELD OF APPLICATION  
 This standard is concerned with methods of test of new tyres for multi -purpose 
vehicles, Lig ht Trucks, Heavy Trucks, Buses and trailers. This standard is not  
applicable for tyre types identified by speed category less than 80km/h. It is also  
not applicable to motor cycle, road equipment or agricultural equipment tyres.  
 
2. COMPLEMENTARY REFERENCES  
2.1 GS 64 5/2009 "Multi -purpose Vehicles, Trucks, Buses  and Tra ilers Tyres  – Part 1 : 
Nomenclature, Designation, Marking, Dimensions, Load Capacity and Inflation 
Pressure  ". 
2.2 GS 647 /2009 "Multi -purpose Vehicles, Trucks, Buses  and Trailers Tyres - Part 3: 
General Requirements".  
 
3. VISUAL INSPECTION  
3.1 Tyres shall be visually inspected to check for the absence of any cracks or cuts in 
the tread or  on either sidewall. Check the tyre for any uneven shape between the 
side walls, by rotating the tyre on a flat surface.  
3.2 The Tyre shall be visually inspected for all th e required marking specified in GSO 
technical regulation mentioned in item 2. 1 
 
4. DIMENSIONS  MEASUREMENT  
4.1 Tyre width  
4.1.1 The tyre shall be mounted on the measuring rim and inflated to the pressure 
specified by the manufacturer for measuring.  
4.1.2 Prior to measuring, it shall be allowed to stand for at least 24 h. at room 
temperature.  
4.1.3 The pressure shall be adjusted to the specified value mentioned in item 4.1.1. 
4.1.4 The tyre width at its maximum point, excluding elevations due to labelling or 
decoration and other edges band by a calliper , shall then be callipered  at six 
different points equally spaced around the circumference.  
4.1.5 The highest measurements shall be taken as the tyre's width.  
 GSO STANDARD  GSO   646    / 
 
2 
  
4.2 Overall diameter  
 The maximum outer circumfer ence shall be measured (under the same conditions 
mentioned in 3. 1) with a steel tape and then divided by 3.1416 in order to 
calculate the overall diameter,  
 
5. STRENGTH TEST  
5.1 Preparation of tyre  
5.1.1  The tyre shall be mounted on the testing rim and inflated to the pressure specified 
by the manufacturer and corresponding to the maximum load of tyre.  An internal 
tube may be used in a tubeless tyre for testing convenience.  
5.1.2  The tyre shall be conditioned at room temperature for at least three hour s. 
5.1.3 The tyre pressure shall be readjusted to the value specified in 5.1.1. 
5.1.4 The tread shall be cleaned and dried before the test . 
5.2 Apparatus  
 A plunger with a compressor of a hemispheric steel end, moving vertically at a 
rate of 50 ± 2.5 mm/mi n., its diameter is chosen according to what is specified in 
Table (1).  
Table (1)  
Ply Rating and Diameter of Plunger  
Load range*  Diameter of plunger mm  
-   Light Truck  19 
- ≤ 12 rim diameter code  19 
 Tubeless :  
 - ≤ 17.5 rim diameter code  19 
- > 17.5 rim diameter code, Load range F or less  32 
- > 17.5 rim diameter code, load range over F  38 
Tube Type :  
Load range F or less  32 
Load range over F  38 
*  See Table (2).  
 
 
 
 
 GSO STANDARD  GSO   646    / 
 
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Table (2)  
Load Range and the Equivalent Ply Rating  
Load range  Ply rating  
A 2 
B 4 
C 6 
D 8 
E 10 
F 12 
G 14 
H 16 
J 18 
L 20 
M 22 
N 24 
 
5.3 Procedure  
5.3 The plunger shall be forced into the tread as near to the centre line of the tyre as 
possi ble, avoiding penetration into a tread groove.  Five or three readings in the 
case of tyres of nominal rim diameter 12 or less of load and penetration at tyre 
break or the plunger is stopped by the rim  ( bottoming of the plunger against the 
rim) shall be m ade at points equally spaced around the circumference of the tyre.  
 
5.4 Calculations  
5.4.1 The breaking energy shall be calculated at each point by means of the following 
formula:  
 
F x P  
W = ————————   x  10–3 
  2 
 Where:  
 W = Energy absorbed at break, N.m  
 F = Force just before breaking, N  
 P = Penetration just before breaking, mm.  GSO STANDARD  GSO   646    / 
 
4 
 5.4.2 The breaking energy of the tyre shall be as the mean value of readings except in 
case the plunger bottoms the rim and the reading is below the minimum specified 
value at  any of the measurement points.  
5.4.3 If, at all of the measuring points, the plunger bottoms on the rim without breaking 
the tyre, the tyre shall be deemed to have passed the test.  
 
6. ENDURANCE TEST  
6.1 Preparation of tyre  
6.1.1 A new tyre shall be mounted on the test rim.  
6.1.2 Inflate the tyre to the pressure specified by  the manufacturer for test pressure 
corresponding to the maximum single tyre load.  
6.1.3 The tyre shall be conditioned at a temperature of (38 ± 3)oC for a period not less 
than 3 hours.  
6.1.4 The inflation pressure shall then be readjusted to the value at which the tyre has  
been previously adjusted as in 6.1.1. 
6.2 Apparatus  
 The apparatus shall consist of the following:  
6.2.1 A steel drum (1700 ± 1%) mm in diameter and of at least the sam e width as the 
tread of the tyre to be tested.  
6.2.2 A spindle on which rim and tyre shall be mounted provided with a means for 
loading the tyre against the test drum.  
6.2.3 A means for rotating the spindle of the drum within the specified testing speeds.  
6.2.4 A means for measuring the radial forces at the spindle of the rim and the tyre at  
different speeds during the test.  
 
6.3 Procedure  
6.3.1 The tyre and the rim shall be mounted on the test axle.  
6.3.2 The test room temperature shall be controlled at (3 8 ± 3)oC during the test.  
6.3.3 If the tyre has load capacity indices for both single and twined utilization, the 
reference load for single utilization shall be taken as the basis for the test load.  
6.3.4 The test shall be carried out at the speeds and loa ds mentioned in Table (3)  shown 
below for tyres with speed category symbol P and less than P.  
 
 
 
 
 GSO STANDARD  GSO   646    / 
 
5 
  
 
 
Table ( 3) 
ENDURANCE TEST PROGRAMME  
Load 
index  Tyre 
speed 
category  Test-drum 
speed  Load placed on the wheel 
as a percentage of the 
load corresponding to th e 
load index  
Radial -
ply rpm  Diagonal  
(bias -
ply) rpm  7 h. 16 h.  24 h.  
122 or 
more  J 150 125 
66% 84% 101%  K 175 150 
L 200 - 
M 225 - 
  4 h. 6 h. 24 h.  
N 275   75% 97% 114%  P 300   
  7 h. 16 h.  24 h.  
121 or 
less J 150 150 66% 84% 101%  K 175 175 
L 200 175 70% 88% 106%  
  4 h 6 h 24 h 
M 250 200 
75% 97% 114%  N 275 - 
P 300 - 
 
 
6.3.5 In the case of tyres with speed category symbol above P, the test procedures shall 
be as shown on item 6.3.8 
6.3.6 The tyre pressure s hall not be corrected through out the test and the test load 
should be kept constant throughout each stages.  
6.3.7 The endurance test shall be carried out without interruption.  
 
6.3.8 Endurance test for tyre with speed category symbol Q and above  
 
  This p rocedure applies to:  
 
6.3.8.1 Tyres marked with load capacity index in single 121 or less.  
 GSO STANDARD  GSO   646    / 
 
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 6.3.8.2 Tyres marked with load capacity index in single 122 and above and with the 
additional marking "C", or "LT".  
 
6.3.8.3 The load shall be placed on the wheel a s a percentage of the load corresponding to 
the load index:  
 
6.3.8.3.1  90% when tested on a test drum 1.70 m ±1 per cent in diameter;  
 
6.3.8.3.2 92% when tested on a test drum 2.0 m ± 1 per cent in diameter.  
 
6.3.8.4 Initial test speed:  Speed corresponding t o the speed category symbol less 20  km/h . 
6.3.8.4.1  Time to reach the initial test speed : 10 min.  
6.3.8.4.2  Duration of the initial test speed : 10 min.  
 
6.3.8.5 Second test speed: Speed corresponding to the speed category symbol less 10 km/h 
for 10  min 
 
6.3.8.6 Final test speed: speed correspondi ng to the speed category symbol for  30 min .  
 
6.3.8.7 Total test duration shall be 1 h.