ھﯿﺌﺔ اﻟﺘﻘﯿﯿﺲ ﻟﺪول ﻣﺠﻠﺲ اﻟﺘﻌﺎون ﻟﺪول اﻟﺨﻠﯿﺞ اﻟﻌﺮﺑﯿﺔ 
GCC STANDARDIZATION ORGANIZATION (GSO)  
 
 
 
 
 
ﻣﺸﺮوع:  ﻧﮭﺎﺋﻲ  
 
 
 
GSO2/1/FDS/GSO 645 : 201 1 
 
 
إطﺎرات اﻟﺴﯿﺎرات ﻣﺘﻌﺪدة اﻷﻏﺮاض واﻟﺸﺎﺣﻨﺎت واﻟﺤﺎﻓﻼت واﻟﻤﻘﻄﻮرات  
اﻟﺠﺰء اﻷول : اﻟﻤﺴﻤﯿﺎت واﻟﺘﻤﯿﯿﺰ واﻟﺒﯿﺎﻧﺎت اﻹﯾﻀﺎﺣﯿﺔواﻷﺑﻌﺎد واﻷﺣﻤﺎل وﺿﻐﻮط  
اﻟﻨﻔﺦ 
Multi -Purpose Vehicles,  Trucks, Buses and  
Trailers - Tyres  Part 1: Nomenclature,  
Designation,  Marking, Dimensions, Load  
Capacities and Inflation Pressures  
 
 
 
 
 
إﻋﺪاد 
اﻟﻠﺠﻨﺔ اﻟﻔﻨﯿﺔ اﻟﻔﺮﻋﯿﺔ اﻟﺨﻠﯿﺠﯿﺔ ﻟﻘﻄﺎع ﻣﻮاﺻﻔﺎت اﻟﻤﺮﻛﺒﺎت واﻹطﺎرات 
  
ھﺬه اﻟﻮﺛﯿﻘﺔ ﻣﺸﺮوع ﻟﻤﻮاﺻﻔﺔ ﻗﯿﺎﺳﯿﺔ ﺧﻠﯿﺠﯿﺔ ﺗﻢ ﺗﻮزﯾﻌﮭ
ﻟﺬﻟﻚ ﻓﺈﻧﮭﺎ ﻋﺮﺿﺔ ﻟﻠﺘﻐﯿﯿﺮ واﻟﺘﺒﺪﯾﻞ، وﻻ ﯾﺠﻮز اﻟﺮﺟﻮع إﻟﯿﮭﺎ ﻛﻤﻮاﺻﻔﺔ ﻗﯿﺎﺳﯿﺔ ﺧﻠﯿﺠﯿﺔ إﻻ ﺑﻌ
اﻋﺘﻤﺎدھﺎ ﻣﻦ ﻣﺠﻠﺲ إدارة اﻟﮭﯿﺌﺔ.   
 
ﺗﻘﺪﯾﻢ  
ھﯿﺌﺔ اﻟﺘﻘﯿﯿﺲ ﻟﺪول ﻣﺠﻠﺲ اﻟﺘﻌﺎون ﻟﺪول اﻟﺨﻠﯿﺞ اﻟﻌﺮﺑﯿﺔ ھﯿﺌ
ﻟﻠﻤﻮاﺻ
ﺑﻮاﺳﻄﺔ ﻟﺠﺎن ﻓﻨﯿﺔ ﻣﺘﺨﺼﺼﺔ .   
  
وﻗﺪ ﻗﺎﻣﺖ ھﯿﺌﺔ اﻟﺘﻘﯿﯿﺲ ﻟﺪول ﻣﺠﻠﺲ اﻟﺘﻌﺎون ﻟﺪول اﻟﺨﻠﯿﺞ اﻟﻌﺮﺑﯿﺔ ﺿﻤﻦ ﺑﺮﻧﺎﻣﺞ ﻋﻤﻞ اﻟﻠﺠﻨاﻟﻔﻨﯿ٢-
١  " ﻟﻠﺠﻨﺔ اﻟﻔﻨﯿﺔ اﻟﺨﻠﯿﺠﯿﺔ ﻟﻘﻄﺎع ﻣﻮاﺻﻔﺎت اﻟﻤﺮﻛﺒ"  ﺑﺘﺤﻟﻤﻮاﺻ
رﻗ٥٤٦/ ٥٠٠٢م،      " إط
اﻟﺠﺰء اﻷول : اﻟﻤﺴﻤﯿﺎت واﻟﺘﻤﯿﯿﺰ واﻟﺒﯿﺎﻧﺎت اﻹﯾﻀﺎﺣﯿﺔ واﻷﺑﻌﺎد واﻷﺣﻤﺎل وﺿﻐﻮط اﻟﻨﻔﺦ  " .وﻗﺎﻣﺖ ﺳﻠﻄﻨﺔ  
ﻋﻤﺎن ﺑﺈﻋﺪاد ﻣﺸﺮوع ھﺬه اﻟﻤﻮاﺻﻔﺔ.    
  
وﻗﺪ اﻋﺘﻤﺪت ھﺬه اﻟﻤﻮاﺻﻔﺔ ﻛـ)ﻣﻮاﺻﻔﺔ ﻗﯿﺎﺳﯿﺔ  / ﻻﺋﺤﺔ ﻓﻨﯿﺔ( ﺧﻠﯿﺠﯿﺔ ﻓﻲ اﺟﺘﻤﺎع ﻣﺠﻠﺲ إدارة اﻟﮭﯿﺌ)           
( ، اﻟﺬي ﻋﻘﺪ ﺑﺘﺎرﯾﺦ      /      /      ھـ ، اﻟﻤﻮاﻓ/    /      م. ﻋﻠﻲ اﻟﻤﻮاﺻ)    /    (  
وﺗَﺤﻞ ﻣﺤﻠﮭﺎ.  
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 regula tions 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. : 645/2005 " Multi -Purpose Vehicles, Truc ks, Buses and Trailers - 
Tyres Part 1: Nomenclature, Designation, Marking, Dimensions, Load Capacities 
and Inflation Pressures" . The Draft Standard has been prepared by Sultanate of 
Oman . 
  
This standard has been approved as a Gulf (Standard / Technical Re gulation)  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  645 /   
 
١ 
   
 
MULTI -PURPOSE VEHICLES, TRUCKS,  
BUSES AND TRAILERS  
TYRES PART 1: NOMENCLATURE, DESIGNATION, 
MARKING, DIMENSIONS, LOAD CAPACITIES AND 
INFLATION PRESSURES  
 
1. SCOPE AND FIELD OF APPLICATION  
 This standard is concerned with nomenclature, designation, marking, dimensions, 
load capacities and  inflation pressures of new tyres for multi -purpose vehicles, 
Light 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 equi pment or agricultural equipment tyres.  
 
2. COMPLEMENTARY REFERENCES  
2.1 GS 51 /2007  "Passenger Car Tyres - Part 1: Nomenclature, Designation, Marking, 
Dimensions, Load Capacity and Inflation Pressures".  
2.2 GS 646 /2009  "Multi -purpose Vehicles, Trucks, Buses  and Trailers, Part 2: Testing 
Methods".  
2.3 GS 647 /2009  "Multi -purpose Vehicles, Trucks, Buses  and Trailers Tyres - Part 3: 
General Requirements".  
 
3. NOMENCLATURE  
 In addition to the following definitions, the definitions mentions in GSO standards 
mentio n in item 2.1 are applicable.  
3.1 Pneumatic tyre  
 Circular shaped tyre made of an elastic material and enforced with steel strand 
and/or fabric and reinforced with suitable fibres or cords and designed to be 
mounted on the rim.  
3.2 Type of pneumatic tyre  
 A category of pneumatic tyres which do not differ in such essential respects as:  
3.2.1  Manufacturer's name or trade mark.  
3.2.2  Tyre size designation.  
3.2.3  Field of use as:  
3.2.3.1  Normal road -use tyres.  GSO STANDARD  GSO  645 /   
 
٢ 
  3.2.3.2  Mud and snow tyres (M + S ).  
3.2.3.3  Specia l-use tyres (off - the - road, ... ). 
3.2.3.4  Use at restricted speed.  
3.2.4  Structure  
3.2.4.1  Diagonal (bias -ply). 
3.2.4.2  Radial . 
3.2.5  Speed symbol or symbols.  
3.2.6  Load capacity index.  
3.2.7  Cross section.  
3.3 Measuring rim  
 The rim on which a tyre sh all be fitted for dimensional measurements.  
3.4 Test rim  
 The rim on which a tyre shall be fitted for strength, speed and endurance tests.  
3.5 Chunking  
 The breaking away of pieces of rubber from tread.  
3.6       Ply 
 A layer of rubber - coated parallel cords.  
3.7 Rim 
 A metallic support for a tyre, or a tyre and tube assembly upon which the tyre bead 
is seated.  
3.8 Ply Rating (PR)  
 Index of tyre strength, does not necessarily represent the actual number of plies in 
the tyre.  It is used to relate a given  size tyre with its load and inflation pressure.  
3.9 Maximum load for a tyre  
 Load for each individual tyre from maximum load applied to the tyres installed on a 
vehicle loaded with the maximum load specified by the manufacturer.  
3.10 Load  index  
 One or tw o numerical codes which indicate the load the tyre can carry in single or 
in single and dual operation at the speed corresponding to the associated speed 
category and when operated in conformity with the requi rements governing 
utilization specified by the tyre manufacturer.  
3.11 Speed symbol  
 A symbol indicating the speed at which the tyre can carry a load corresponding to 
its load index under the service conditions specified by the tyre manufacturer.  
 
4. DESIGNATION  GSO STANDARD  GSO  645 /   
 
٣ 
   It shall be as specified in the GSO  standard mentioned in 2.1, or in the publications 
of at least  one of the organizations specified in 6.4, in addition to the following 
items:  
4.1 Tyres shall be designated according to the maximum speed using the letters 
mentioned in Table (1).  
 
 
Table (1)  
Max imum Speed and Corresponding Symbol  
for Tyre Designation  
Speed symbol  F G J K L M N P Q R S T U H V 
 
Corresponding 
speed km/h  
80  
90  
100  
110  
120  
130  
140  
150  
160  
170  
180  
190  
200  
210 More 
than 
210 
 
 
4.2 Nominal rim diameter  
 In addition to the  nominal diameters indicated in the GSO  standard mentioned in 
2.1, the following values shall be added to this standard:  
 
Nominal rim diameter  
(mm)  Figure to be used as tyre 
designation (inch) 
508 20 
533 21 
559 22 
610 24 
635 25 
318 12.5 
343 13.5 
368 14.5 
394 15.5 
419 16.5 
445 17.5 
495 19.5 
521 20.5 GSO STANDARD  GSO  645 /   
 
٤ 
  572 22.5 
622 24.5 
660 26 
711 28 
762 30 
 
 
4.3 Load  index  
 In addition to the load indices mentioned in the GSO  standard mentioned in 2.1 the 
following values shall be added to this standard:  
 
Tyre 
load 
(Kg)  Load 
index  Tyre 
load 
(Kg)  Load 
index  Tyre 
load 
(Kg)  Load 
index  Tyre load 
(Kg)  Load  
index  
1450  121 2575  141 4625  161 8250  181 
1500  122 2650  142 4750  162 8500  182 
1550  123 2725  143 4875  163 8750  183 
1600  124 2800  144 5000  164 9000  184 
1650  125 2900  145 5150  165 9250  185 
1700  126 3000  146 5300  166 9500  186 
1750  127 3075  147 5450  167 9750  187 
1800  128 3150  148 5600  168 10000  188 
1850  129 3250  149 5800  169 10300  189 
1900  130 3350  150 6000  170 10600  190 
1950  131 3450  151 6150  171 10900  191 
2000  132 3550  152 6300  172 11200  192 
2060  133 3650  153 6500  173 11500  193 
2120  134 3750  154 6700  174 11800  194 
2180  135 3850  155 6900  175 12150  195 
2240  136 4000  156 7100  176 12500  196 
2300  137 4125  157 7300  177 12850  197 
2360  138 4250  158 7500  178 13200  198 
2430  139 4375  159 7750  179 13600  199 
2500  140 4500  160 8000  180 14000  200 GSO STANDARD  GSO  645 /   
 
٥ 
   
 
5. MARKING  
 Each tyre shall be legibly and indelibly marked, with characters of a minimum height of 
2 mm (for words) and 4 mm (for numbers), with the following infor mation in either 
Arabic and/or English arranged as follows : 
5.1 The manufacturer's name or trade mark;  
5.2 The tyre -size designation  
5.3 The speed -category symbol (or symbols);  
5.4 The load indices;  
5.5 The word "TUBELESS" if the tyre is designed for use w ithout an inner tube;  
5.6 The date of manufacture in the form of a group of four digits, the first two showing the 
week and the last two the year of manufacture.  
5.7 In the case of tyres which can be regrooved, the symbol "  " at least 20 mm in 
diameter, or the word "REGROOVABLE", moulded into or on to each sidewall;  
5.8 The suffix "C"  or "LT" in the tyre size designation marking,  or the word "LIGHT 
TRUCK" on the tyre sidewall,  if applicable . 
5.9 Country of Production  
5.10 Tread Wear Indicator  
 
6. DIMENSIONS, LOAD CAPACITIES AND INFLATION PRESSURES  
6.1 Section width  
6.1.1  The section width shall be obtained by means of the following formula, (which 
applies to tyres with a metric size designation.  For tyres with a code size 
design ation, item 6.3 applies).  
 
S = S 1 + K (A – A1) 
 
Where:  
S = is the section width expressed in millimetres and measured on the measuring 
rim. 
S1 =  is the nominal section width in millimetres, as shown on the sidewall of the 
tyre in the tyre designation as p rescribed.  
A = is the width of the measuring rim in millimetres, as specified by the  
manufacturer.  
A1=  is the width of the theoretical rim in millimetres.  GSO STANDARD  GSO  645 /   
 
٦ 
  A1  shall be taken equal to S 1 multiplied by the factor x as prescribed by the tyre 
manufacturer and  K shall be taken equal to 0.4.  
6.1.2  The overall width of a tyre may be less than the section width determined in 
accordance with item 6.1.1  
6.1.3  The overall  width  may exceed by 4% in case of radial ply tyres and by 8% in case 
of diagonal (bias -ply) tyre s.  However, for tyres of a section width exceeding 305 
mm intended for dual mounting (twinning), the nominal value shall not be 
exceeded by more than 2% for radial ply tyres with nominal aspect ratio higher 
than 60 or 4% for diagonal (bias -ply) tyres.  
6.2 Outer diameter  
6.2.1  The outer diameter of a tyre shall be obtained by means of the following formula, 
(which appliels to tyres with a metric size designation, for tyres with a code size 
designation, item 6.3 applies).  
 
                                      D = d 1 + 0.02 × (S 1× R a) 
                                                                                            
Where:  
D  is the outer diameter expressed in millimetres.  
d1  is the conventioal number denoting the nominal diameter of  the rim (in mm).  
S1  is the nominal section width in millimetres.  
Ra  is the nominal aspect ratio,  
6.2.2  The outer diameter of a tyre must not be outside the values Dmin and Dmax 
obtained from the following formulae:  
 
    Dmin = d + (2H x a)  
    Dmax = d + (2H x b)  
    where H = 0.5 (D -d) 
 
  Coefficients "a" and "b" are respectively:  
 
  Coefficient "a" = 0.97  
 
Coefficient "b"  Radial  Diagonal  
normal use tyres  1.04 1.07 
for special use tyres  1.06 1.09 
 
     
          
 
6.3 For the existing types of tyres w hose designation is given in publications mentioned 
in 6.4, the section width and the outer diameter shall be as mentioned in those 
publications.  GSO STANDARD  GSO  645 /   
 
٧ 
  6.4 Dimensions load, capacities and inflation pressures shall be in accordance with 
what is mentioned in curre nt publications, at the date of manufacture of the tyre or 
any later date, of at least one of the following organizations:  
6.4.1  "The Tyre and Rim Association TRA in USA".  
6.4.2  "The European Tyre and Rim Technical Organization ETRTO".  
6.4.3  "Japan Automob ile Tyre Manufacturers Association JATMA".  
6.4.4  "Deutsches Institut Fur Normung (DIN)".  
6.4.5  "British Standards Institution".  
6.4.6  "Scandinavian Tyre and Rim Organization STRO".  
6.4.7  "The Tyre and Rim Organization of Australia".  
6.4.8     "Association Francaise de Normalisation AFNOR" -