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The Executive Director Uganda National Bureau of Standards P.O. Box 6329 Kampala Uganda Tel: 256 41 505 995 Fax: 256 41 286 123 E-mail: [email protected] Web: www.unbs.go.ug
Uganda National Bureau of Standards (UNBS) is a parastatal under the Ministry of Trade, Industry and Cooperatives established under Cap 327, of the Laws of Uganda, as amended. UNBS is mandated to co-ordinate the elaboration of standards and is (a) a member of International Organisation for Standardisation (ISO) and
(b) a contact point for the WHO/FAO Codex Alimentarius Commission on Food Standards, and
(c) the National Enquiry Point on TBT Agreement of the World Trade Organisation (WTO).
The work of preparing Uganda Standards is carried out through Technical Committees. A Technical Committee is established to deliberate on standards in a given field or area and consists of representatives of consumers, traders, academicians, manufacturers, government and other stakeholders.
Draft Uganda Standards adopted by the Technical Committee are widely circulated to stakeholders and the general public for comments. The committee reviews the comments before recommending the draft standards for approval and declaration as Uganda Standards by the National Standards Council. This Draft Uganda Standard, DUS EAS 357: 2004, Pneumatic tyres for trucks and buses — Specification, is identical with and has been reproduced from an East African Standard, EAS 357: 2004, Pneumatic tyres for trucks and buses — Specification, and is being proposed for adoption as a Uganda Standard.
This standard cancels and replaces US 514:2004, Specification for new pneumatic tyres — Trucks and buses.
This Uganda Standard, DUS EAS 357: 2004, has been developed by the Transport and communication standards Technical Committee (UNBS/TC 8).
Wherever the words, “East African Standard" appear, they should be replaced by "Uganda Standard."
Foreword Development of the East African Standards has been necessitated by the need for harmonizing requirements governing quality of products and services in East Africa. It is envisaged that through harmonized standardization, trade barriers which are encountered when goods and services are exchanged within the Community will be removed.
In order to achieve this objective, the Partner States in the Community through their National Bureaux of Standards, have established an East African Standards Committee.
The committee is composed of representatives of the National Standards Bodies in Partner States, together with the representatives from the private sectors and consumer organizations. Draft East African Standards are circulated to stakeholders through the National Standards Bodies in the Partner States. The comments received are discussed and incorporated before finalization of standards, in accordance with the procedures of the Community.
East African Standards are subject to review, to keep pace with technological advances. Users of the East African Standards are therefore expected to ensure that they always have the latest versions of the standards they are implementing.
Introduction This East African Standard has been prepared in order to give the necessary specifications and requirements for test of pneumatic tyres. It provides important information to be observed for improvement of motor vehicle safety in the country. In reporting the results of a test made in accordance with this East African Standard, if the final value observed or calculated is to be rounded off, it shall be done in accordance with EAS 124, Rounding off numerical values. In the preparation of this East African Standard, assistance was derived from the following documents: BS AU 50-1.2.1a:1995, Tyres and wheels — Specification for metric series tyres — Commercial vehicle tyres, published by the British Standards Institution. ISO 4209-1:2001, Truck and bus tyres and rims (metric series) — Part 1: Tyres ISO 10454:1993(E), Truck and bus tyres — Verifying tyre capabilities — Laboratory test methods, published by the International Organization for Standardization.
Some company standards from our local industries.
Acknowledgement is hereby made for the assistance derived from these sources.
Pneumatic tyres for trucks and buses — Specification 1 Scope This East African Standard specifies tyre dimensions designation and marking requirements; and load ratings. It also gives laboratory test requirements for strength endurance for tyres primarily intended for trucks and buses. 2 Application This standard applies to new pneumatic tyres bias-belted, diagonal and radial mounted on 5° tapered rims and on 15° tapered (drop-centre) rims for use on trucks and buses. It does not apply to any tyre which has been reconditioned; or to any tyre which has been altered so as to render impossible its use, or its repair for use, as motor vehicle equipment. 3 References This East African Standard makes reference to the following documents: EAS 124, Rounding off numerical values EAS 53, Tyre reconditioning — Specification EAS 358, Pneumatic tyres for passenger cars — Specification 4 Terminology For the purpose of this standard, the definitions given in EAS 53 and EAS 358 shall apply. 5 General requirements 5.1 Materials The basic compound used in the tyre construction shall be of natural rubber, synthetic rubber, or a combination thereof. 5.2 Retread ability The tyre construction shall be of a type that allows for retreading to the tyre casing. 5.3 Ozone resistance Each tyre as part of production shall contain sufficient anti-oxidants and anti-ozonants to provide standard commercial resistance to weathering. 5.4 Temperature ability Each tyre shall have an inherent capability of acceptable performance in ambient air temperatures ranging from 49 °C to – 40 °C. 5.5 Workmanship A tyre covered under this specification shall show no evidence of poor workmanship. All plies, belts, bead, and breakers shall be smooth and evenly laid and shall be free of buckles, wavy cord, air pockets and any other anomalies or imperfections, which may impair serviceability.
5.6 Age of rubber Tyre covered under this specification shall not be more than 8 years from the date of manufacture. 6 Tyre designation The designation of the tyre shall be shown on its sidewall and shall include the following markings, to be shown close to each to other:
a) size and construction; and b) service condition characteristics.
6.1 Size and construction The size and construction shall be indicated as follows: Nominal Nominal Tyre Nominal section aspect construction rim diameter width ratio code code or Nominal Nominal Tyre Nominal section aspect construction rim width ratio code diameter 6.1.1 Nominal section width The nominal section width shall be expressed in millimetres (or equivalently in inches). For tyres fitted to 5° taper rims and 15° taper rims (code- designated), the nominal tyre section width shall end in 5. 6.1.2 Nominal aspect ratio The nominal aspect ratio shall be expressed as a percentage and shall be a multiple of 5. 6.1.3 Tyre construction code The tyre construction code shall be as follows:
B for bias – belted construction D l – for diagonal/bias construction R for radial construction
6.1.4 Nominal rim diameter The nominal rim diameter shall be expressed by a code for 5° tapered bead seat rims and 15° tapered bead seat (drop–centre rims (see table 1 for code correlations). 6.2 Service condition characteristics The characteristics shall be indicated as follows;
Load index / Load index Speed symbol single / dual
The load index is a numerical code associated with maximum load a tyre can carry at the speed indicated by its speed symbol under the service conditions specified by the tyre manufacturer. 6.3 Other service characteristics 6.3.1 The word “TUBELESS” shall appear on the tyre to characterize tyres that can be used without a tube. 6.3.2 An arrow to indicate direction of rotation if preferred. 6.3.3 In case of special tread tyres the symbol “EY” shall be shown on the tyre. 6.3.4 Each tyre shall be labeled with the name of manufacturer/brand name and recognized quality/safety mark to show that the tyre conforms to respective national standards. The tyre may be also be marked with any other identification assigned to the manufacturer. 6.4 Example A tyre having
a) A size and construction of :
i) nominal section width 275 mm, ii) nominal aspect ratio 70 %,
iii) radial construction,
iv) nominal rim diameter code 22.5,
b) Service condition characteristic of :
i) single load 2 500 kg,
ii) dual load 2 300 kg,
iii) reference speed 130 km/h,
c) other service characteristics
ii) special tread,
shall be marked
275/70R 22.5 I 1440/137 M
7 Tyre dimensions 7.1 Calculation “of design tyre” dimensions For the choice of coefficients K, (rim section ratio) and K2 (see Table 2). 7.1.1 Theoretical rim width, Rth
The theoretical rim width, Rth , is equal to the product of the nominal section width , SN and the rim/section ration K1, Rth = K1 SN. 7.1.2 Measuring rim width Rm The measuring rim width, Rm is the width of the existing rim nearest to the theoretical rim width, R th (see table 3) for the rim widths of 5° tapered and 15° tapered (drop-center) rims. 7.1.3 Design tyre section width, S The design tyre section width, S is the nominal section width, SN transferred from the theoretical rim, Rth to the measuring rim, Rm. S = SN + K2 (Rm – Rth) Rounded to the nearest whole number. 7.1.4 Design tyre section height, H The design section height, H is equal to the product of the nominal section width, SN and the nominal ratio H/S (H/S as %)
100H N SHS /
Rounded to the nearest whole number. 7.1.5 Design tyre overall diameter, Do The design tyre overall diameter, Do is the sum of the nominal rim diameter, Dr, plus twice the design tyre section height. Do = Dr + 2H For those tyres using a nominal rim diameter code, see table 1 (a) for the value of Dr, to be used 7.1.6 Values The relevant dimensions for the metric series of truck and bus tyre measuring rim width, design section width and design section height are shown in annexes A and B for tyres of a given series, with a nominal tyre section over 205, it is recommended that they should be in increments larger than 10. 7.2 Calculation of “maximum overall tyre dimensions in service” These calculations are for use by vehicle manufacturers in designing for tyre clearances. 7.2.1 Maximum overall width in service, W max. The maximum overall width in service, W max is equal to the product of the design section width, S, and the appropriate coefficient, a (see Table 2).
W max. =Sa It includes protective ribs, lettering, embellishments, manufacturing tolerances and growth due to service. 7.2.2 Maximum overall diameter in service, Do, max.
The maximum overall diameter in service, Do max is equal to the nominal diameter, Dr, plus twice the product of the design tyre section height, H and the appropriate coefficient, b (see Table 2).
D o max = Dr + 2 Hb It includes manufacturing tolerances, the different tyres of tread patterns and growth due to service. 7.3 Minimum dual spacing (MDS) 7.3.1 The minimum dual spacing is a guideline value equal to the product of the design tyre section width, S, and appropriate coefficient K3 (see Table 2b). MDS = SK3 It is referred to as tyre load according to the load index, in dual application shown in the service characteristics on the tyre at an inflation pressure applicable for normal highway service. 7.3.2 The design tyre section width, S, will change 2.5 mm for each 0.25 change in rim width code. The minimum dual spacing shall be adjusted accordingly. 7.4 Permitted rim widths The range of permitted rim widths, in millimetres is determined for each nominal section width, by multiplying the nominal section width, SN by the coefficients CR, presented in Table 3.
i.e. minimum rim width: CR min. x SN maximum rim width : CR max. SN
8 Tyre dimension tables Example of few sizes in a tyre dimension table are shown in C.2 and C.3. The figures shown in the column headed “Rim” are codes related to measuring rim width, R m (see Table 1 (AB) for code correlations). 9 Load ratings 9.1 Tyre load – carrying capacity See Table 4 for load indices 9.2 Speed symbols See Table 5 speed symbols 9.3 Load — carrying capacity at various speeds When the tyre is fitted on a vehicle with a maximum speed capability different from the tyre reference speed, variations of load are granted in relation to the load corresponding to the load index (Table 6). To obtain improved operating performance under these conditions, inflation pressures higher than the basic pressure may be required.
Table 2 — Coefficients for calculation of tire dimensions
a) Coefficients K2, b, a. Structure Tyre construction code Coefficients Bias – belted Diagonal Radial
a) Coefficients K1, K3 Tyre construction
code Type of
rim Nominal aspect
Rim/section ratio K1
Minimum dual spacing K3
5 ° tapered 100 to 65 0.70 1.15
15° tapered 90 to 65 0.75 1.125
Table 3 — Coefficients for calculation of rim widths for truck and bus tyres related to nominal
aspect ratio H/S
Coefficients for calculation of recommended rim width
Type of rim
Nominal aspect ratio H/S
Nominal section width
15° tapered 65 ≤ H/S ≤ 100
All 0.65 0.80
75 ≤ H/S ≤ 90
≥ 225 0.675 0.80 15° tapered
65 ≤ H/S ≤ 70 All 0.675 0.85 10 Test requirements 10.1 Test sample – two tyres of identical characteristics shall comprise a test sample.
a) one tyre shall be used for the measurement of strength; and b) a second tyre for the endurance test.
10.2 Test equipment The test equipment shall constitute the following items: 10.2.1 Test drum, cylindrical driven flywheel (drum) — having a diameter of 1.7 m ± 1 % or 2 m ± 1 %; the surface of which is made of smooth steel. The width of the test surface shall be equal or greater than the overall width of the test tyre. For the test drum, the loading device may be a dead-weight cantilevered system with a hydraulic or pneumatic system. The accuracy shall be within ± 1.5 % of the full scale; the speed capability of the equipment shall be adequate for the requirements of the test methods. The accuracy of the test drum speed shall be within + 2 km /h at the full scale.
10.2.2 Plunger, cylindrical steel plunger of sufficient length with a hemispherical end and a diameter as shown in Table 7 with reference to the tyre load index. For the plunger equipment, the loading device shall permit gradual application of the force. Indicators of displacement and of force shall be provided with accuracy within ± 3 % of the full scale. 10.2.3 Inflation pressure gauges, with a maximum scale value of at least 1000 kPa with accuracy within ± 20 kPa. 10.3 Testing 10.3.1 Strength test 10.3.1.1 Requirement — Each test sample shall meet at least the requirements for minimum breaking energy specified in Table 8 when tested in accordance with 10.3.1.3 10.3.1.2 Preparation of the tyre — The tyre is mount on a test rim and inflated to the pressure specified for the maximum load rating in single formation, or maximum dual load, when they differ. The assembly is maintained at test room temperature for at least 3 h. 10.3.1.3 Test procedure — The pressure is readjusted to that specified in 10.3.1 and the assembly mount on a fixture. The plunger is positioned as near to the centreline as possible, avoiding penetration into the tread grooves; and forced perpendicularly into the tread at a rate of 50 mm/min. ± 2.5 mm/min. The force and penetration at the moment of breaking are recorded, at each of five test points approximately equally spaced around the circumference of the tyre. The pressure should be checked before moving to the next test point. If the tyre fails to break before the plunger is stopped on reaching the rim and the required minimum breaking energy is not achieved, then the tyre is deemed to have passed the test at that point. The breaking energy W, in joules for each test point is computed using the following formula:
F = force in Newton P = penetration in mm
The breaking energy value for the tyre is obtained by taking the average values. 10.3.2 Endurance test 10.3.2.1 Requirement — When the tyre has been subjected to the laboratory endurance test using the procedure in 10.3 2.3, using a test rim and a valve which undergo no permanent deformation and allows no loss of air, there shall be no visual evidence of tread, sidewall, ply cord innerliner, belt or bead separation, chuking, open splices, cracking or broken cords. The tyre pressure measured immediately after the test shall not be less than the initial pressure specified in 10.3.2.2. 10.3.2.2 Preparation of tyre — The tyre is mount on a test rim and inflated to the pressure corresponding to the maximum load rating. The tyre and rim assembly is maintained at eminent temperature, which shall be at least 20 °C, for at least 3 h.
10.3.2.3 Test procedure — The tyre pressure is readjusted to the value specified in 10.3.2.2 immediately before testing. Then the tyre and rim assembly is mount on a test axle so that the tyre may be pressed radially against the outer face of the test drum. During the test, the ambient temperature shall be maintained at between 20 °C and 30 oC or at a higher temperature if the tyre manufacturer agrees. Each successive phase of the test shall be conducted without interruptions, at a test speed with loads and test periods as shown in:
a) table 8a for tyres width load index (single) up to 121 inclusive and speed symbol up to P; b) 10.3.2.4 for tyres with load index (single up to 121 inclusive and speed symbols Q and above; c) Table 8b for tyres with load index (single) 122 and above.
Throughout the test, the inflation pressure shall not be corrected and the test load shall be kept constant. 10.3.2.4 Specific conditions for tyre with speed symbol Q and above — The load applied shall be:
a) 90 % of the maximum load rating on 1.7 m drum diameter; b) 92 % of the maximum load rating on 2 m drum diameter.
The initial test speed shall be equal to the tyre's speed category minus 20 km/h. The equipment shall be operated in such a way that the drum speed is brought up to the initial test speed over a period of 10 min. The equipment is operated with the test drum speed at the initial test speed for 10 min, then at the initial speed plus 10 km/h for at least 10 min and finally at the tyre’s speed category for 30 min; the total duration of the test being 1 h. 11 Nonconforming tyres No tyre that is designed and manufactured for use on buses and trucks, that does not conform to the requirements of this standard shall be sold, offered for sale, introduced or delivered for introduction into, or imported into the East Africa Community, for any purpose.
Guideline values for metric series, 5° rims A.1 The values given in table A.1 are for information. A.2 These values will serve as a guideline for design of tyre dimensions, metric series, mounted on 5° tapered drop-centre rims (code-designated) with nominal rim diameters up to code 16 inclusive. For tyres mounted on 15° tapered drop-centre rims (code-designated), see Annex B. For tyres mounted on deferent types of rims (millimetre-designated), other annexes will be established. Table A.1 — Dimensional guidelines for metric “100” to “75” series tyres on 5° tapered rims
Tyre design dimensions, mm
Design section height a , H
Measuring rim width code Rm
Design section width S Nominal aspect ratios, H/S
Approved rim width codes
mm 100 95 90 85 80 75 min. max.
125 3.50 126 125 119 113 106 100 94 3 4
135 3.50 133 135 128 122 115 108 101 3.5 4.5
145 4.00 145 145 138 131 123 116 109 3.5 4.5
155 4.50 157 155 147 140 132 124 116 4 5
165 4.50 165 165 157 149 140 132 124 4 5
175 5.00 177 175 166 158 149 140 131 4.5 5.5
185 5.00 184 185 176 167 157 148 139 4.5 6
195 5.50 196 195 185 176 166 156 146 5 6
205 5.50 203 205 195 185 174 164 154 5 6.5
215 6.00 216 215 204 194 183 172 161 5.5 7
225 6.00 223 225 214 203 191 180 169 6 7
235 6.50 235 235 223 212 200 188 176 6 7.5
245 7.00 248 245 233 221 208 196 184 6.5 7.5
255 7.00 255 255 242 230 217 204 191 6.5 8
265 7.50 2.67 265 252 239 225 212 199 7 8.5
275 7.50 274 275 261 248 234 220 206 7 8.5
285 8.00 286 285 271 257 242 228 214 7.5 9
295 8.00 294 295 280 266 251 236 221 7.5 9.5
305 8.50 306 305 290 275 259 244 229 8 9.5
315 8.50 313 315 299 284 268 252 236 8 10
325 9.00 325 325 309 293 276 260 244 8.5 10
335 9.00 333 335 318 302 285 268 251 8.5 10.5
345 9.50 345 345 328 311 293 276 259 9 11
355 10.00 357 355 337 320 302 284 266 9 11
365 10.00 364 365 347 329 310 292 274 9.5 11.5
a The figures are based on normal tread pattern tyres.
Guideline values for metric series, 15° rims B.1 The values given in table B.1 are for information. B.2 These values will serve as a guideline for design of tyre dimensions, metric series, mounted on 15° rims tapered drop-centre rims (code-designated). For tyres mounted on 15° tapered drop-centre rims (code-designated), see Annex A. For tyres mounted on different types of rims (millimetre-designated) other annexes will be established.
Table B.1 — Guideline values for metric series, 15° rims
Nominal section width a b
Measuring rim width
Design section width
Design section height c, H mm Approved rim width codes d
SN Rm S Nominal aspect ratios, H/S
Nominal aspect ratios, H/S 90 to 70
Nominal aspect ratio,
H/S 65 mm mm 90 85 80 75 70 65 min. max. min. max.
Continue Continue with either "option a" with either "option b" or "option b" or "option c"
Option a Option b Option c 345 335 325 375 365 355 405 395 385 435 425 415 ... 455 445 ... ... ... b These lists are open-ended. For other nominal tyre section widths, SN, lower than 175 or higher than 445, other
annexes will be established as necessary. c The figures are based on normal tread pattern tyres.
d Other rims may be specified in relation to special services by agreement among tyre, rim, wheel and motor vehicle manufacturers
C.1 The dimensions given in this annex are for information. C.2 Example of dimension table of a tyre having nominal section width 185, nominal aspect ration 90, radial, nominal rim diameter code 16, mounted on 5° tapered rim:
Design tyre Maximum tyre dimensions in - service
Tyre size designation
Measuring rim width code
D o max.
185/90 R 16
753 C.3 Example of dimension table of a tyre having nominal section width 265, nominal aspect ratio 75, diagonal, nominal rim diameter code 19.5 mounted on 15° tapered rim (drip-centre):
Maximum tyre dimensions in - service
Tyre size designation
Measuring rim width
Section width S
D o max
mm 265/ 75 D 19.5
C.4 Example of dimension table of a tyre having nominal section width 305, nominal aspect ratio 45, construction Z, nominal rim diameter 500, mounted on a new concept rim with rim/section ratio 0,5:
Test conditions for tyres with non-standard marking For an interim period, it is permissible for tyres not to be marked with a load index, but with a “load range” or equivalent ply rating “PR” marking. Table D1 and D2 apply in place of Tables 7 and 8 respectively.
Table D.1 – Plunger diameter
Tyre marked “LT” Tyres with rim diameter code ≤ 12 Tyres with rim diameter code ≤ 17.5 and marked “TUBELESS”
Other than above: — Tyres marked LOAD RANGE F (or 12PR) and below — Tyres marked LOAD RANGE F (or 12PR) and over
Table D.2 – Endurance test
Percentage of maximum load rating
Marking of speed restricted service
7 h (Period 1)
C,D E to L
6; 8 10 to 20
A to D
E F G
H to N
2 to 8
10 12 14
16 to 24
250 200 200 175 150
75 1) 70 66 66 66
88 84 84 84
114 106 101 101 101
1) 4 h for tyres with rim diameter code 14.5 or less. 2) 6 h for tyres with rim diameter code 14.5 or less.