1、BRITISH STANDARD BS ISO 9112:2008 Truck and bus tyres Methods of measuring tyre rolling circumference Loaded new tyres ICS 43.080.01; 83.160.10 BS ISO 9112:2008 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 March 2008 BSI 2008 ISBN 978 0
2、 580 58436 7 National foreword This British Standard is the UK implementation of ISO 9112:2008. It supersedes BS AU 50-1.2.2:1991 which is withdrawn. The UK participation in its preparation was entrusted to Technical Committee AUE/4, Tyres and wheels for motor vehicles. A list of organizations repre
3、sented on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard cannot confer immunity from legal obligations. Amendmen
4、ts/corrigenda issued since publication Date CommentsINTERNATIONAL STANDARD ISO 9112 Second edition 2008-02-15 Reference number ISO 9112:2008(E) Truck and bus tyres Methods of measuring tyre rolling circumference Loaded new tyres Pneumatiques pour vhicules utilitaires et autobus Mthodes de mesure de
5、la circonfrence de roulement Pneumatiques neufs en chargeBS ISO 9112:2008 ii iii Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
6、 ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborate
7、s closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards
8、. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this
9、 document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 9112 was prepared by Technical Committee ISO/TC 31, Tyres, rims and valves, Subcommittee SC 4, Tr u c k and bus tyres and rims. This second edition cancels and replaces
10、 the first edition (ISO 9112:1991), which has been technically revised. BS ISO 9112:2008 iv Introduction The distance covered by a vehicle in a straight line in one wheel revolution is information that is increasingly used by the electronic systems in vehicles. One reason is that it makes it possibl
11、e to indicate the instantaneous vehicle speed to the driver. Its evaluation uses the rolling circumference of the tyre in normal usage conditions: tyre deflected by the carried load and inflated to an adapted pressure level. A standardized measuring method is necessary because some parameters, such
12、as tyre load and pressure, can cause the rolling circumference to change. This International Standard contributes to tyres being interchangeable for a given vehicle. Its application by tyre manufacturers allows confidence to be maintained in the information provided to the driver, especially concern
13、ing speed and distance travelled. BS ISO 9112:2008 1 Truck and bus tyres Methods of measuring tyre rolling circumference Loaded new tyres 1S c o p e This International Standard specifies two methods for measuring the rolling circumference and the number of revolutions per unit distance (kilometre) o
14、f new commercial vehicle tyres, under loaded conditions, for use on trucks and buses. The first method is a drum method consisting of loading a test tyre mounted on a free axle against a driven road wheel (or drum) of specified diameter. The second method involves a vehicle whose drive axle is equip
15、ped with the test tyres driven on a straight, paved road. 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. NOTE This International Standard applies not only to large truck and bus tyres, but also to
16、 small truck and bus tyres, which are called “light truck tyres” in some countries. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of th
17、e referenced document (including any amendments) applies. ISO 4209-1, Truck and bus tyres and rims (metric series) Part 1: Tyres 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 revolutions per unit distance number of tyre revolutions (and por
18、tions thereof) that occur when the (axle) centre of the tyre is moved exactly the unit distance of , under the conditions specified in this International Standard 3.2 rolling circumference of tyre distance that the (axle) centre of the tyre moves in one revolution of the tyre, under the conditions s
19、pecified in this International Standard 3.3 reference speed speed at which the test is intended to be performed and which is related to the delivered value of the rolling circumference 1km BS ISO 9112:2008 2 4 Drum method 4.1 Principle A test tyre mounted on a free axle is loaded against a driven ro
20、ad wheel (drum) of specified diameter. The value of the rolling circumference is determined for a specified speed; the tyre and drum revolutions are counted and used in the formula to determine the tyres rolling circumference. 4.2 Test drum specifications 4.2.1 Diameter The test drum shall have a di
21、ameter of at least , with a free axle capable of holding and loading a tyre against the driven drum. Care shall be taken to avoid low frequency bouncing. 4.2.2 Surface The surface of the drum should preferably be of smooth steel. In cases where a textured drum surface is used, this shall be noted in
22、 the test report. The surface of the drum shall be kept clean. 4.2.3 Width The width of the drum surface shall exceed that of the test tyre tread. 4.3 Thermal environment The test should preferably be carried out at a reference room temperature of . However, it may be performed in the range to . No
23、temperature correction is required. 4.4 Test speed 4.4.1 Test speed for load index 122 and above In order to establish a basic reference for rolling circumference for all tyres, the rolling circumference shall be given for a drum speed of for tyres with speed symbols K to M inclusive, and for a drum
24、 speed offor tyres with speed symbols F to J. For tyres that bear the mandatory marking “max. speed ” or “max. speed ”, and for tyres not marked with a speed symbol, the drum speed shall be . For radial tyres, the measurements can be performed within the speed interval from to , and the end result m
25、ay be calculated by linear interpolation. 4.4.2 Test speed for load index 121 and below In order to establish a basic reference for rolling circumference for all tyres, the rolling circumference shall be given for a drum speed of . NOTE This also applies to tyres without speed symbol on the sidewall
26、. For radial tyres, the measurements can be performed within the speed interval from to , and the end result may be calculated by linear interpolation. 1,7 m 25 C 20 C 30 C 80 km/h 60 km/h 55 mph/88 km/h 50 mph/80 km/h 60 km/h 30 km/h 130 km/h 80 km/h 30 km/h 130 km/h BS ISO 9112:2008 3 4.5 Accuracy
27、 The minimum number of impulses ( ) per revolution of both the tyre and the drum shall be 10. The total number of impulses during the time of measurement should be greater than 1 000. 4.6 Test tyre parameters 4.6.1 Load The standard test load shall be of the maximum single load capacity of the tyre.
28、 4.6.2 Alignment The specific values are shown in Annex A. 4.6.3 Inflation pressure The inflation pressure of the test tyre at ambient temperature shall be the inflation pressure, specified by the tyre manufacturer concerned, corresponding to the maximum single tyre load capacity. The pressure shall
29、 be capped. 4.7 Rims The rims used in the test should be of a size and type approved by the tyre manufacturer for use with the test tyre. If such rims are not available, or if the information is unknown, a standard measuring rim, or the rim nearest in size and type to it, shall be used in the test.
30、4.8 Procedure 4.8.1 To ensure repeatability of measurements, an initial break-in and cooling period can be necessary prior to the start of the test. Such a break-in should be carried out on a test drum of at least in diameter, for a period of at least , at the reference test speed of or , whichever
31、applies in accordance with 4.4, with the load and inflation pressure as specified in 4.6.1 and 4.6.3 respectively. 4.8.2 For future comparisons, record the overall diameter of the new tyre after the break-in. 4.8.3 Allow the tyre to stand, inflated, in the test area thermal environment in order for
32、it to achieve thermal equilibrium, generally reached after . 4.8.4 Adjust the inflation pressure to that specified in 4.6.3. After about , verify that the load is as specified in 4.6.1. 4.8.5 Rotate the drum at the test speed for at least , in order to warm up the tyre and reach thermal equilibrium.
33、 After warm-up, the inflation pressure may not be readjusted under capped-pressure conditions, and the test shall be run with pressure build-up to simulate normal service conditions. The values obtained under regulated pressure conditions will be similar to those obtained using capped pressure. 4.8.
34、6 Record the number of revolutions (and portions thereof) of both tyre and drum that occur during a time duration, . For tyre as well as for drum, the total number of impulses during the time should be greater than 1 000. N i 85 % 1,7 m 1h 60 km/h 80 km/h 6h 10 min 90 min T T BS ISO 9112:2008 4 4.9
35、Calculation Calculate the rolling circumference of the test tyre, , in millimetres, as follows: where is the number of revolutions of the drum; is the number of revolutions of the tyre; is the radius of the drum, in millimetres. 5 Test method using vehicle 5.1 Principle This method consists of drivi
36、ng 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. 5.2 Test course The test course shall be a level,
37、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 should be or longer, depending on the accuracy of the test equipment as specified in 5.5. The l
38、ength of the test course, expressed in metres, shall be measured to within . 5.3 Test temperature and wind speed The ambient temperature shall be between and . However, an asphalt surface shall be sufficiently cool so that the surface is not tacky. The wind speed shall not exceed . 5.4 Test speed 5.
39、4.1 Test speed for load index 122 and above The speed shall be for tyres with speed symbols K to M inclusive, and for speed symbols F to J inclusive. For tyres that bear the mandatory marking “max. speed ” or “max. speed ”, and for tyres not marked with a speed symbol, the test speed shall be . 5.4.
40、2 Test speed for load index 121 and below The test speed shall be . NOTE This also applies to tyres without a speed symbol on the sidewall. C r C r = 2(N d /N t )R N d N t R 1% 500 m 0,1 % 5 C 30 C 3 m/s 80 km/h 2 km/h 60 km/h 2 km/h 55 mph/88 km/h 50 mph/80 km/h 60 km/h 2 km/h 80 km/h 2 km/h BS ISO
41、 9112:2008 5 5.5 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 . 5.6 Vehicle for measurements 5.6.1 Test vehicle and tyre positions The test vehicle shall be representative
42、 of the type used with the tyre size being tested. The test 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 n
43、ormally used as duals on drive axles shall be tested as duals. 5.6.2 Test load The load on the drive axle shall be of the maximum rated tyre load ( of maximum dual load rating for tyre sizes normally used as duals on drive axles) multiplied by the number of tyres on the axle, within . The tyre maxim
44、um load capacity is the value corresponding to the load index moulded on the sidewall of the tyre. NOTE When the tyre is not marked in this way, it is advisable that the literature provided by the tyre manufacturer be consulted for the maximum load capacity at the speed indicated by the speed symbol
45、 rating of the tyre. The load on the other axle should be as obtained with normal load distribution. 5.7 Tyres and rims 5.7.1 Test tyres The test tyres shall be a matched set of the same size designation, type and brand having inflated unloaded overall diameters within of each other. For future comp
46、arisons with other tyres, record the overall diameter of the new tyres. This shall be measured as specified in ISO 4209-1. 5.7.2 Tyre inflation pressure The inflation pressure of the test tyres at ambient temperature shall be that pressure corresponding to the maximum load capacity (maximum dual loa
47、d capacity for tyre sizes normally used as duals on drive axles) specified by the manufacturer. 5.7.3 Test rims The rims shall be of the size and type approved by the tyre manufacturer for use with the test tyre in highway service. In the absence of such information, the rim nearest or equivalent to
48、 the size and type of the standardized measuring rim shall be chosen. 0,1 % 85 % 85 % 2% 0,5 % BS ISO 9112:2008 6 5.7.4 Tyre break-in Prior to the test, the test tyres shall be conditioned by running at least , at the reference test speed of or as applicable, with the load and inflation given in 5.6
49、.2 and 5.7.2 respectively. After break-in, the tyres shall not have more than loss of tread depth. 5.8 Procedure 5.8.1 After the tyres have been broken in as specified in 5.7.4, allow the tyres to stand inflated at the ambient temperature of the test area for at least . During this time, the tyre and wheel assembly may be installed on the test vehicle. 5.8.2 Adjust the inflation to the pressure specified in
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