BRITISH STANDARD AUTOMOBILE SERIES BS AU 50 1 3 1993 ISO 8767 1992 Tyres and wheels — Part 1 Tyres — Section 1 Car tyres — Subsection 1 3 Method of measuring rolling resistance Reproduced by IHS under[.]
BRITISH STANDARD AUTOMOBILE SERIES BS AU 50-1 3:1 993 ISO 8767:1 992 Tyres and wheels — Part : Tyres — Section : Car tyres — Subsection Method of measuring rolling resistance 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 3:1 993 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 (Inc) Motor Cycle Industry’s Association of Great Britain Ltd Motor Industry Research Association National Tyre Distributors’ Association Retread Manufacturers’ Association Road Haulage Association Ltd Society of Motor Manufacturers and Traders Ltd 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 January 993 Amd No © BSI 2- 999 The following BSI references relate to the work on this standard: Committee reference AUE/4 Draft for comment 89/73799 DC ISBN 80 21 22 Reprodu ced by I H S u n d er l i cen se wi th BSI - U n trol l ed Copy Date Comments BS AU 0-1 3:1 993 Contents Page Committees responsible National foreword Inside front cover ii Scope Definitions Test methods Test equipment Test conditions Test procedure Data interpretation Data analysis Annex A (normative) Test equipment tolerances Annex B (informative) Optional test conditions Annex C (informative) Measurement methods of moment of inertia for drum and tyre assembly — Deceleration method Figure — Free- body diagram of tyre/drum system, © BSI 2- 999 Reprodu ced by I H S u n d er l i cen se wi th BSI - U n trol l ed Copy assuming no bearing and windage losses Figure C — Arrangement Figure C — Spring method Figure C — Bifilar pendulum (rope) method Table B i BS AU 0-1 3:1 993 National foreword This Subsection of this Part of BS AU 50 has been prepared under the direction of the Automobile Standards Policy Committee and is identical with ISO 8767: 992 Pas senger car tyres — Methods of m easuring rolling resistance, published by the International Organization for Standardization (ISO) Other Parts of this standard are as follows: — Part 2: Wheels and rim s; — Part 3: Valv es; — Part 4: Rim p rofiles and dim ensions 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 to 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 0-1 3:1 993 2.5 Scope This International Standard specifies methods for parasitic loss measuring rolling resistance, under controlled loss of energy (or energy consumed) per unit laboratory conditions, for new pneumatic tyres distance excluding tyre losses, and attributable to designed primarily for use on passenger cars The aerodynamic loss, bearing friction and other sources relationship between values obtained and the fuel of systematic loss which may be inherent in the economy of the vehicle is undetermined, and such measurement values are not intended to be used to indicate levels 2.6 of performance or quality skim reading This International Standard applies to all type of parasitic loss measurement, in which the passenger car tyres tyre is kept rolling, without slip page, while It enables comparisons to be made between the reducing the tyre load to a level at which energy loss rolling resistance of new tyres when they are within the tyre itself is virtually zero free- rolling straight ahead, in a position perpendicular to the drum outer surface, and in steady- state conditions In measuring tyre rolling resistance, it is necessary to measure small forces in the presence of much larger forces It is, therefore, essential that 2.7 machine reading type of parasitic loss measurement, involving losses of the test machine, exclusive of losses in the rotating spindle which carries the tyre and rim equipment and instrumentation of appropriate 2.8 accuracy be used moment of inertia (see Annex C) Definitions For the purposes of this International Standard, the following definitions apply 2.1 rolling resistance: The following alternative measurement methods are given in this International Standard The choice F of an individual method is left to the tester For each r loss of energy (or energy consumed) per unit of distance NOTE Test methods method, the test measurements shall be converted to a rolling resistance force acting at the tyre/drum interface The SI unit conventionally used for the rolling resistance is the newton metre per metre (N·m/m) This is equivalent to the drag force in newtons (N) 2.2 rolling resistance coefficient: C r a) Force method: the reaction force at the tyre spindle b) Torque method: the torque input to the test drum ratio of the rolling resistance, in newtons, to the load c) Power method: the power input to the test on the tyre, in newtons This quantity is drum dimensionless and is derived as follows: d) Deceleration method: the deceleration of the C r = rolling resistance test load 2.3 capped inflation process of inflating the tyre and allowing the test drum and tyre assembly Test equipment 4.1 Drum specifications 4.1 Diameter inflation pressure to build up, as the tyre is warmed The test dynamometer shall have a cylindrical up while running flywheel (drum) with a diameter of between , m 2.4 regulated inflation process of inflating the tyre to the required pressure independent of its temperature, and maintaining and m inclusive It should be noted that the results are different; see 8.3 for drum diameter correction for comparisons, if necessary 4.1 Surface this inflation pressure while the tyre runs under The surface of the drum shall be smooth steel or load This is most commonly done by using a textured and shall be kept clean For the textured regulated pressure source attached to the tyre drum surface, see B.4 through a rotating union (See Annex B ) © BSI 2- 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 -1 : 993 4.1 Width Test inflation p ressure The width of the drum test surface shall exceed the The inflation pressure shall be the inflation width of the test tyre tread pressure, specified by the tyre manufacturer concerned, corresponding to the maximum tyre load capacity reduced by 30 kPa The inflation pressure The tyre shall be mounted on a test rim, as specified shall be capped with the accuracy specified in in Annex A When the deceleration method is selected, the following requirements apply: Measurement of these parameters shall be a) for duration, %t, the time increments shall not sufficiently accurate and precise to provide the exceed 0,5 s; required test data The specific and respective b) any variation of the test drum velocity shall not values are shown in Annex A exceed km/h Te st rim A D uration and ve locity Load, alignme nt, control and instrume ntation accuracies The rmal e nvironme nt Reference conditions O ptional conditions If the sensitivities of load, inflation or velocity are The reference ambient temperature, as measured desired, additional information given in on the rotational axis of the tyre, m away from the Annex Bthe should be consulted plane touching the nearest tyre sidewall, shall be 25 °C Alternative conditions The test procedure steps described below are to be If the reference temperature cannot be obtained, the followed in the sequence given rolling resistance measurement shall be corrected to standard temperature conditions in accordance To ensure repeatability of measurements, an initial with break-in and cooling period is required prior to the Drum surface temperature start of the test Such a break-in should be carried Care should be taken to ensure that the out on a vehicle or on a test drum of at least 1,5 m temperature of the test drum surface is diameter for a period of at least h, at a minimum approximately the same as the ambient velocity of 80 km/h, with the load and inflation temperature at the beginning of the test pressure given in and respectively 4.4.1 Test procedure 4.4.2 Bre ak-in 4.4.3 5 Test conditions The test consists of a measurement of rolling resistance in which the tyre is inflated and the inflation pressure allowed to build up (i.e., “capped air”) Te st spe eds 5.1 Single test velocity The value shall be obtained at a drum velocity of 80 km/h 5.1 Multiple test velocity The values shall be obtained at drum velocities of 50 km/h, 90 km/h and 120 km/h Test load 5.3 Thermal conditioning Place the inflated tyre in the thermal environment of the test location for the time necessary to achieve thermal equilibrium which is generally reached after h Pre ssure adj ustment After thermal conditioning, the inflation pressure shall be adjusted to the test pressure, and verified 10 after the adjustment was made Warm-up The tyre shall be run at constant test velocity until reaching a stabilized steady-state value of rolling resistance Recommendations for warm-up periods are given in Annex B The standard test load shall be computed from 80 % of the maximum load capacity of the tyre and shall The following shall be measured and recorded be kept within the tolerance specified in Annex A (see Figure 1): a) test velocity, Un; b) load on the tyre normal to the drum surface, Lm ; Me asureme nt and re cording 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 -1 : 993 c) test inflation pressure: ) initial, as defined in , a) Remove the tyre from the drum surface U , record the input torque, T , the power, or the test drum deceleration, 2) final, for capped inflation; b) At the test velocity, T , the tyre spindle force, F , the input power, V × A, or d) the driving torque on the drive shaft, the deceleration of the test drum/tyre/wheel whichever applies Deceleration method 6 %Ê/%t, depending on the method; ); e) distance, r (see ; f) ambient temperature, t g) test drum radius, R; n p t t assembly, a) Remove the tyre from the test surface L Machine reading 6 b) Record the deceleration of the test drum, %Ê /%t, and that of the unloaded tyre, %Ê /%t amb o po D ata interpretation h) test method chosen; i) test rim (designation and material) Sub traction of parasitic losses The parasitic losses shall be subtracted as shown in 7.1 , 7.1 or 7.1 Skim reading 7.1 Subtract the skim reading from the test measurement Machine reading 7.1 Subtract the machine reading from the test measurement Parasitic losses 7.1 Calculate the parasitic losses, F , in newtons as p where I is the test drum inertia in rotation, in D R Ê kilogram metres squared; is the test drum surface radius, in metres; vo %t is the test drum angular velocity, without tyre, in radians per second; o is the time increment chosen for the measurement of the parasitic losses without tyre, in seconds; I T Figure — Fre e -b ody diagram of tyre /drum system, assuming no b e aring and windage losses 6 to r po is the tyre angular velocity, unloaded tyre, Rolling re sistance calculation Determine parasitic losses by the procedure given 6 kilogram metres squared; is the tyre rolling radius, in metres; in radians per second 6 Me asure ment of p arasitic losse s in R Ê is the tyre and wheel inertia in rotation, in 6 The net values of driving torque, spindle force, power or deceleration are to be converted to rolling Skim reading resistance, a) Reduce the load to maintain the tyre at the test F , expressed in newtons, using the r appropriate method, as shown in 7.2.1 to 7.2.4 velocity without slippage to, for example, 50 N b) Record the spindle force, F , input torque, T , p p or the power, whichever applies c) Record the load on the tyre normal to the drum surface, L p © BSI 2- 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 3:1 993 Force method 7.2.1 The rolling resistance, Annex C gives guidelines and practical examples to F , in newtons, is calculated r with the equation F = F [1 + (r /R) ] r t 8.1 Rolling resistance coefficient F r is the tyre spindle force, in newtons; t is the distance from the tyre axis to the L drum outer surface under steady- state conditions, in metres; is the test drum radius, in metres Torque method 7.2.2 The rolling resistance, F , in newtons, is calculated r T R = r = V F , in newtons, is calculated r V× A U 3, r is the rolling resistance, in newtons; m is the test load, in newtons n F , in newtons, is calculated r kilogram metres squared; is the test drum surface radius, in metres; is the time increment chosen for measurement, in seconds; is the test drum angular velocity, loaded tyre, in radians per second; is the tyre and wheel inertia in rotation, in T r AP F [1 + K(t = r amb – 25)] F t is the rolling resistance, in newtons; is the ambient temperature, in degrees Celsius; K is equal to 0, 01 for car tyres 8.3 Drum diameter correction formula: F Ò KF r02 r01 with where is the test drum inertia in rotation, in I F Test results obtained from different drum diameters where v is the may be compared by using the following theoretical with the equation v r25 hour The rolling resistance, D F rolling resistance at 25 ° C, in newtons: is the test drum velocity, in kilometres per Deceleration method I using the following equation, where amb machine drive, in amperes; U then a correction for temperature shall be made r is the electric current drawn by the P F L where machine drive, in volts; R M F r where r25 is the electrical potential applied to the A Ê F L = is the test drum radius, in metres where R %t r are unavoidable (only temperatures not less n 7.2.4 C than 20 ° C not more than 30 ° C are acceptable), with the equation r tyre: is the input torque, in newton metres; The rolling resistance, F r If measurements at temperatures other than 25 ° C Power method 7.2.3 C , is calculated by dividing the rolling resistance by the load on the 8.2 Temperature correction where T R The rolling resistance coefficient, m with the equation F method Data analysis L where R measure the moments of inertia for the deceleration R R r F T r01 F r02 is the radius of drum , in metres; is the radius of drum 2, in metres; is the nominal tyre radius, in metres; is the rolling resistance value measured on drum , in newtons; is the rolling resistance value measured on drum 2, in newtons kilogram metres squared; is the tyre rolling radius, in metres; is the tyre aerodynamic torque; is as defined in 7.1 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 3:1 993 Annex A (normative) Test equipment tolerances A.1 Purpose The limits specified in this annex are necessary in order to achieve suitable levels of repeatable test results, which can also be correlated among various test laboratories These tolerances are not meant to represent a complete set of engineering specifications for test equipment: instead, they should serve as guidelines for achieving reliable test results 0,5 km/h for the force method; — time: ± 0,02 s — angular velocity: ± 0,2 % A.4.2 Optional compensation for load /spindle force interaction and load misalignment ± NOTE This compensation applies for the force method only Compensation of both load/spindle force interaction (“crosstalk”) and load misalignment may be accomplished either by recording the spindle force for both forward and reverse tyre rotation or by dynamic machine calibration If spindle force is recorded for forward and reverse directions (at each A.2 Test rims test condition), compensation is achieved by A.2.1 Width subtracting the “reverse” value from the “forward” value and dividing the result by two If dynamic The test rim width shall be equal to the standardized measuring rim If this is not available, machine calibration is intended, the compensation then the next wider rim may be chosen It should be terms may be easily incorporated in the data reduction noted that a change in rim width will result in different test results A.5 Instrumentation accuracy A.2.2 Runout The instrumentation used for readout and recording of test data shall be accurate within the tolerances Runout shall meet the following criteria: stated below: — maximum radial runout: 0,5 mm — tyre load: ± 10 N — maximum lateral runout: 0,5 mm — inflation pressure: ± kPa A.3 Alignment — spindle force: ± 0,5 N Angle deviations are critical to the test results — torque input: ± 0,5 N·m A.3.1 Load application — distance: ± mm The direction of tyre loading application shall be — electrical power: ± 10 W kept normal to the test surface and shall pass through the wheel centre within — temperature: ± 0,2 °C — mrad for the force and deceleration methods; — surface velocity: ± 0,1 km/h (for all methods) — mrad for the torque and power methods — time: ± 0,01 s A.3.2 Tyre alignment — angular velocity: ± 0,1 % A.3.2.1 Camber angle A.6 Test surface roughness The plane of the wheel shall be normal to the test The roughness, measured laterally, of the smooth surface within mrad for all methods steel drum surface shall have a maximum centreline average height value of 6,3 4m A.3.2.2 Slip angle A.7 Tyre spindle bearing friction The plane of the tyre shall be parallel to the direction of the test surface motion within mrad When using the machine reading as a method for for all methods determining the parasitic losses, tyre spindle bearing friction should be regularly verified as being A.4 Control accuracy sufficiently small as to be considered negligible A.4.1 General accuracy (e.g a coastdown from 80 km/h to km/h in not less Exclusive of perturbations induced by the tyre and that with a freely rotating tyre) rim non-uniformities, the test equipment shall be capable of checking the test variables within the following limits: — tyre loading: ± 20 N — inflation pressure: ± kPa — surface velocity: ± 0,2 km/h for the power, torque and deceleration methods, © 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 BS AU 50-1 3:1 993 Annex B (informative) Optional test conditions C.2.1 Equipment needed The arrangement shown in Figure C requires, in addition to the drum and its angular encoder: B.1 Purpose — a lightweight pulley mounted on low- friction The rolling resistance of a tyre will vary with velocity, load and inflation pressure, as well as other factors Depending upon the circumstances of particular tyre applications, it can be useful to determine the effect of these tyre- related bearings; — a weight of known mass, — suitable wire rope and attachments Experimental arrangement parameters for the individual tyre to be tested If C.2.1 such information is desired, the options indicated See Figure C in B.2 and B.3 are recommended Unless otherwise noted, all aspects of the standard test conditions apply m , in the range 50 kg to 00 kg; C.2.1 Theory Application of laws of mechanics to the system shown in Figure C leads to the following equation: B.2 Speed sensitivity Tests are carried out at 50 km/h, 90 km/h and 20 km/h, in sequence (see 5.1 ) A warm- up period of at least 30 for the first velocity and at least 20 for each successive velocity is required B.3 Load and inflation sensitivity The recommended loads and inflation pressures are given in Table B A warm- up period of at least 30 for the first data point and at least for each successive data point are required m I is the mass, in kilograms; is the pulley inertia, in kilogram metres P squared; r R I is the pulley radius, in metres; is the drum radius, in metres; is the drum inertia, in kilogram metres D B.4 Textured surface In cases where a textured drum surface is used instead of a smooth steel surface, this fact shall be noted in the test report The surface texture shall then be 80 where 4m deep (80 grit) squared; C is the friction torque of drum bearings, in newton metres; g is the earth’s gravity equal to 9, 81 m/s ; %Ê /%t is the angular acceleration or D deceleration Table B.1 Tyre load as a Test inflation pressure: NOTE percentage of standardized pressure, neglected maximum load modified: 50 + 70 kPa, regulated 50 – 30 kPa, regulated 90 + 70 kPa, regulated 90 – 30 kPa, regulated The friction torque of pulley bearings, c, can be Annex C (informative) Measurement methods of moment of inertia for drum and tyre assembly — Deceleration method C.1 Limitation The methods presented here should be considered only as guidelines or practical examples of methods used to measure moments of inertia by the deceleration method to achieve reliable test results C.2 Test drum inertia C.2.1 Measurement method Reprodu ced by I H S u n d er l i cen se wi th BSI - U n trol l ed Copy Figure C.1 — Arrangement © BSI 2- 999 BS AU 50-1 3:1 993 C.2.1 Method m, is released, the angular When the mass, acceleration is measured through the angular encoder fitted to the drum axle (and otherwise used to measure drum decelerations) The friction torque, C, of drum bearings can also be measured, provided that the rope can be separated from the drum once mass, m, has given sufficient C.3.1 Theory Equation of free movement of pendulum, if Ú is the angle from equilibrium: I d d t Ú + KÚ = Natural oscillation period, T: momentum to the drum, for the subsequent drum deceleration is directly related to I D %Ê D %t = dec C by: C where Ú where the values are as defined C.2.1 C.2.2 Determination method The drum inertia is estimated by calculation The drum inertia, I , in kilogram metres squared, is D determined by the summation of the inertia of each drum part (flange, disc, reinforced rib): I D = I+I +I f d t I is the period of time, in seconds; is the torsion pendulum inertia, in kilogram metres squared; K is the spring constant C.3.1 Method Measurement of oscillation periods, with the tyre T , and without, T , can be used to give I K T – T assembly, r the tyre assembly inertia, where I I I is the angle of oscillation, in radians; f is the drum flange inertia; d is the drum disc inertia; r is the reinforced rib inertia; all values being expressed in kilogram metres I T = C.3.2 ; 2 T Bifilar pendulum (rope) method Tyre inertia can be obtained by the period time of squared twisted oscillation of a tyre hanging from two steel C.3 Tyre assembly inertia ropes of exactly the same length (see Figure C 3) C.3.1 Spring method C.3.1 Equipment needed Torsion pendulum of inertia K (see Figure C 2) I and spring constant Figure C.2 — Spring method Figure C.3 — Bifilar pendulum (rope) method C.3.2.1 Theory The tyre inertia, I , in kilogram metres squared, is T determined by © BSI 2- 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 3:1 993 I T Ù × = Wab ; h where Ù W a C 3.2.2 Method The time p eriod, Ù , of the twis ted os cillation of a tyre is meas ured, and tyre inertia can b e calculated from the equation given in C.3.2.1 is the oscillation p eriod, in s econds ; is the tyre and wheel weight, in newtons ; is the distance b etween p oints A and B, in metres ; b is the dis tance b etween p oints C and D , in metres ; h is the vertical dis tance b etween lines AB and C D , in metres Reprodu ced by I H S u n d er l i cen se wi th BSI - U n trol l ed Copy © BS I - 99 blank 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 3:1 993 ISO 8767:1 992 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 technical committee res p ons ib le, the identity of which can b e found on the inside front cover Tel: 02 89 96 90 00 Fax: 02 89 96 40 BS I offers memb ers an individual up dating s ervice called PLUS which ens ures that s ub s crib ers automatically receive the lates t editions of s tandards Buying standards O rders for all BS I, international and foreign s tandards p ub lications s hould b e addres s ed to C us tomer S ervices Tel: 899 00 Fax: 899 7001 In res p ons e to orders for international standards , it is BS I p olicy to sup p ly the BS I imp lementation of thos e that have b een p ub lis hed as Britis h S tandards, unless otherwis e requested Information on standards BS I p rovides a wide range of information on national, E urop ean and international standards through its Lib rary and its Technical H elp to E xp orters S ervice Various BS I electronic information s ervices are also availab le which give details on all its p roducts and s ervices C ontact the Information C entre Tel: 02 89 96 71 1 Fax: 02 89 96 048 S ub s crib ing memb ers of BS I are kep t up to date with s tandards develop ments and receive sub s tantial discounts on the p urchase p rice of s tandards For details of thes e and other b enefits contact Memb ership Adminis tration Tel: 02 89 96 70 02 Fax: 02 89 96 00 Copyright C op yright s ub s is ts in all BS I p ub lications BS I als o holds the cop yright, in the UK, of the p ub lications of the international s tandardization b odies E xcep t as p ermitted under the C op yright, D es igns and Patents Act 988 no extract may b e rep roduced, s tored in a retrieval s ystem or transmitted in any form or b y any means – electronic, p hotocop ying, recording or otherwis e – without p rior written p ermis s ion from BS I This does not p reclude the free us e, in the cours e of imp lementing the standard, of necess ary details such as s ymb ols, and size, typ e or grade designations If thes e details are to b e used for any other p urp os e than imp lementation then the p rior written p ermiss ion of BS I must b e ob tained If p ermis sion is granted, the terms may include royalty p ayments or a licensing agreement D etails and advice can b e ob tained from the C op yright Manager BS I 89 C his wick H igh Road London W4 4AL Reprodu ced by I H S u n d er l i cen se wi th BSI - U n trol l ed Copy Tel: 02 89 96 70