BRITISH STANDARD AUTOMOBILE SERIES BS AU 50 1 2 2 1991 ISO 9112 1991 Tyres and wheels — Part 1 Tyres — Section 2 Commercial vehicle tyres — Subsection 2 2 Method of measuring tyre rolling circumferenc[.]
BRITISH STANDARD AUTOMOBILE SERIES BS AU 50-1 2.2:1 991 ISO 91 2:1 991 Tyres and wheels — Part : Tyres — Section 2: Commercial vehicle tyres — Subsection 2.2 Method of measuring tyre rolling circumference — Loaded new tyres Reprodu ced by I H S u n d er l i cen se wi th BSI - U n trol l ed Copy BS AU 50-1 2.2:1 991 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Automobile Standards Policy Committee (AUE- ) to Technical Committee AUE/4, upon which the following bodies were represented: Agricultural Engineers’ Association Automobile Association British Industrial Truck Association British Pressure Gauge Manufacturers’ Association British Rubber Manufacturers’ Association Bus and Coach Council Department of Transport Freight Transport Association Institute of Road Transport Engineers (Incorporated) Motor Cycle Industry’s Association of Great Britain Ltd Motor Industry Research Association National Tyre Distributors’ Association Retread Manufacturers’ Association Road Haulage Association Ltd Royal Automobile Club Society of Motor Manufacturers’ and Traders This British Standard, having been prepared under the direction of the Automobile Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on Amendments issued since publication 29 November 991 © BSI 2- 999 The following BSI references relate to the work on this standard: Committee reference AUE/4 Draft for comment 89/78450 DC ISBN 80 202 87 Reprodu ced by I H S u n d er l i cen se wi th BSI - U n trol l ed Copy Amd No Date Comments BS AU 50-1 2.2:1 991 Contents Page Committees responsible National foreword © BSI 2- 999 ii Scope Normative reference Definitions Principle Measurement requirements Vehicle for measurements Tyres and rims Procedure Calculations Publication(s) referred to Reprodu ced by I H S u n d er l i cen se wi th BSI - U n trol l ed Copy Inside front cover Inside back cover i BS AU 50-1 2.2:1 991 National foreword This Subsection of this Part of BS AU 50 has been prepared under the direction of the Automobile Standards Policy Committee It is identical with ISO 91 2: 991 “Truck and b us tyres — Method of m easuring tyre ro lling , published by the International Organization circum ference — Lo aded new tyres” for Standardization (ISO) Other Parts of this standard are: — Part 2: Wheels and rim s; — Part 3: Valv es Cross-references The Technical Committee has reviewed the provisions of ISO 4209- : 988 to which reference is made in the text and has decided that they are acceptable for use in conj unction with this standard NOTE It is anticipated that the full provisions of ISO 4209- will be implemented in a future revision of BS AU 50- when revision work now taking place in ISO has been completed A British Standard does not purport to include all the necessary provisions of a contract Users of British Standards are responsible for their correct application Compliance with a British Standard does not of itself confer immunity from legal obligations Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages and 2, an inside back cover and a back cover This standard has been updated (see copyright date) and may have had amendments incorporated This will be indicated in the amendment table on the inside front cover ii Reprodu ced by I H S u n d er l i cen se wi th BSI - U n trol l ed Copy © BSI 2- 999 BS AU 50-1 2.2:1 991 Scope This International Standard specifies the method for measuring rolling circumference and revolutions per unit distance (kilometre) for new tyres, under loaded conditions, made for use on trucks and buses The values thus obtained are not intended for use as levels of performance or quality This International Standard applies to all truck and bus tyres Normative reference The following standard contains provisions which, through reference in this text, constitute provisions of this International Standard At the time of publication, the edition indicated was valid All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent edition of the standard indicated below Members of IEC and ISO maintain registers of currently valid International Standards ISO 4209-1:1988, Truck and bus tyres and rims (metric series) — Part 1: Tyres Definitions For the purposes of this International Standard, the following definitions apply 3.1 revolutions per unit distance number of tyre revolutions (and portions thereof) that occur when the (axle) centre of the tyre is moved exactly the unit distance of km, under the conditions specified below 3.2 rolling circumference of tyre distance that the (axle) centre of the tyre moves in one revolution of the tyre under the conditions specified below Principle The measurement method consists of driving a typical vehicle equipped with the test tyres on the drive axle, on a straight, level, paved road at a constant speed, and counting the number of tyre revolutions (or portions thereof) that occur while traversing an accurately measured distance © BSI 12-1999 Reprodu ced by I H S u n d er l i cen se wi th BSI - U n trol l ed Copy Measurement requirements 5.1 Test course The test course shall be a level, straight section of smooth, dry road surfaced with either asphalt or concrete pavement of medium roughness The longitudinal and transverse gradient of the road shall be at most % The length of the course shall be 500 m or longer depending on the accuracy of the test equipment as specified in 5.4 The length of the test course, expressed in metres, shall be measured to within 0,1 % 5.2 Weather during test The ambient temperature shall be between °C and 30 °C; however, an asphaltic surface shall be sufficiently cool that the surface is not tacky The wind speed shall not exceed m/s 5.3 Test speed For tyres with a speed symbol — G (90 km/h) and above, the test speed shall be 70 km/h ± km/h; — below G or with a maximum speed marking lower than 90 km/h, the test speed shall be approximately 75 % ± km/h of such a speed NOTE When tyres are not marked with a speed symbol, the test should be at 70 km/h ± km/h Test equipment accuracy The minimum number of impulses per revolution shall be 16 The overall error in the revolution-counting equipment including start and stop errors shall not exceed 0,1 % Vehicle for measurements 6.1 Test vehicle and tyre positions The vehicle shall be representative of the size used with the tyre size being tested The vehicle shall have only two axles Since most speedometers and odometers are actuated from the drive-shaft, the test tyres shall be fitted to the drive axle For four-wheel drive vehicles, one axle shall be disengaged Tyre sizes that are normally used as duals on drive axles shall be tested as duals BS AU 50-1 2.2:1 991 Drive the vehicle at the test speed for approximately 60 to warm up the tyres After The load on the drive axle shall be 80 % of the warm-up, the inflation pressure shall not be maximum rated tyre load (80 % of maximum dual readjusted: the test is run with pressure build-up to load rating for tyre sizes normally used as duals on drive axles) times the number of lyres on the axle, simulate normal service conditions 8.4 Run the test immediately at the test speed within ± % specified in over the test course specified in 5.1 The tyre maximum load capacity is the value This requires an approach road at both ends of the corresponding to the load index moulded on the test course to allow the course to be entered at the sidewall of the tyre test speed NOTE When not so marked, the tyre manufacturer literature should be consulted for the maximum load capacity at the speed Acceleration, braking, and steering shall be kept to indicated by the speed symbol rating of the tyre an absolute minimum during the measurements The load on the other axle should be as obtained 8.5 Record the number of revolutions (and portions with normal load distribution thereof) of the right test wheel and the left test wheel that occur over the test course Tyres and rims 8.6 Repeat the test to a total of traversing the course 7.1 Test tyres twice in each direction 7.1 The tyres shall be a matched set of the same 8.7 If the number of revolutions for each wheel on size designation, type, and brand having inflated the second run differs from the first run in the same unloaded overall diameters within 0,5 % of each direction by more than 0,2 %, repeat the test until other two runs are obtained in each direction with the number of revolutions within 0,2 % for each wheel 7.1 For future comparisons with other tyres, record the overall diameter of the new tyres This Calculations shall be measured as specified in ISO 4209-1 6.2 Test load 8.3 7.2 Tyre inflation pressure 9.1 Accuracy The inflation pressure of the tyre at ambient temperature shall be that pressure corresponding to the maximum load capacity (maximum dual load capacity for tyre sizes normally used as duals on drive axles) specified by the manufacturer 7.3 Tyre break-in Prior to the test, the tyres shall be conditioned by running at least 150 km at an average speed of approximately 70 km/h at the load and inflation specified in 6.2 and 7.2 respectively After break-in, the tyres shall not have more than 10 % loss of tread depth A calculation is made for each of the eight readings (i.e four runs for each drive wheel) that comply with the accuracy requirements of 8.7 The eight calculated figures are then averaged to obtain the rated value The revolutions per unit distance (see 9.2 ) and the rolling circumference (see 9.3 ) are then rounded to the nearest unit 9.2 Revolutions per unit distance The number of tyre revolutions per unit distance is determined by dividing the measured revolutions (and portions thereof) by the measured distance traversed in the test Thus the number of 7.4 Test rims revolutions per kilometre is given by the expression: The rims shall be of the size and type approved by Measured revolutions- × 10 the tyre manufacturer for use with the test tyre in Test course length highway service In the absence of such information, the rim nearest or equivalent to the standardized where the test course length is expressed in metres measuring rim shall be chosen 9.3 Rolling circumference The rolling circumference is determined by dividing Procedure the length of the test course by the number of 8.1 After the tyres have been broken in as indicated revolutions Thus the rolling circumference, in in 7.3 , allow the tyres to stand inflated at the millimetres, is given by the expression: ambient temperature of the test area for at Test course length - × 10 least h During this time, the tyre and wheel Measured revolutions assembly may be installed on the test vehicle where the test course length is expressed in metres 8.2 Adjust the inflation to the pressure specified in 7.2 The load shall be that specified in 6.2 Reprodu ced by I H S u n d er l i cen se wi th BSI - U n trol l ed Copy © BSI 12-1999 BS AU 50-1 2.2:1 991 Publication(s) referred to See national foreword © BSI - 999 Reprodu ced by I H S u n d er l i cen se wi th BSI - U n trol l ed Copy BS AU 0-1 2.2:1 991 ISO 91 2:1 991 BSI — British Standards Institution BS I is the indep endent national b ody res p ons ib le for p rep aring Britis h S tandards It p res ents the UK view on s tandards in E urop e and at the international level It is incorp orated b y Royal C harter Revisions Britis h S tandards are up dated b y amendment or revis ion Us ers of Britis h S tandards should make s ure that they p oss es s the latest amendments or editions It is the constant aim of BS I to imp rove the quality of our p roducts and services We would b e grateful if anyone finding an inaccuracy or amb iguity while us ing this Britis h S tandard would inform the S ecretary of the 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