Bsi bs au 050 2 7a 1995 (1999)

BRITISH STANDARD AUTOMOBILE SERIES Tyres and wheels — Part 2: Wheels and rims — Section 7a: Code of practice for the selection and care of tyres and wheels for commercial vehicles BS AU 50-2.7a: 1995 BS AU 50-2.7a:1995 Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee AUE/4, Tyres and wheels for motor vehicles, 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 Confederation of Passenger Transport UK 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 Engineering Sector Board, was published under the authority of the Standards Board and comes into effect on 15 December 1995 © BSI 03-1999 Amendments issued since publication First published March 1987 Second edition December 1995 Amd No The following BSI references relate to the work on this standard: Committee reference AUE/4 Draft for comment 95/701902 DC ISBN 580 25160 Date Comments BS AU 50-2.7a:1995 Contents Page Committees responsible Inside front cover Foreword ii 7.1 Scope 7.2 References 7.3 Tyre and wheel selection 7.4 Tyre selection 7.5 Wheel selection 7.6 Wheel fixings 7.7 Care and maintenance of wheels and tyres 7.8 Wheel fitting and nut tightening procedure Annex A (informative) Bus and truck tyre sidewall markings Annex B (informative) Types of rims and wheels 11 Annex C (informative) Types of flanges, spring flanges and locking rings 19 Figure — Wheel fixings Figure — Sequence of stud tightening Figure A.1 — Bus and truck tyre sidewall markings Figure B.1 — Wide base rims 12 Figure B.2 — Flat base rims 13 Figure B.3 — Semi drop centre (SDC) rims 14 Figure B.4 — 15° drop centre rims 15 Figure B.5 — 5° well base rim 15 Figure B.6 — Divided rim 16 Figure B.7 — Earlier and later types of tubeless wheels 17 Figure B.8 — Single wheel offset 18 Figure B.9 — Dual (twin) wheel offset or half dual spacing 18 Figure C.1 — Cross-sections of typical flanges and locking rings 20 Table A.1 — Load index values 10 Table A.2 — Speed symbol values 10 List of references Inside back cover © BSI 03-1999 i BS AU 50-2.7a:1995 Foreword This Section of BS AU 50 has been prepared by Technical Committee AUE/4, and gives guidance to vehicle users on the selection of replacement tyres and wheels for commercial vehicles and on the care of tyres, wheels and wheel fixings It is a revision of BS AU 50-2.7:1987, which is withdrawn This revision updates the recommendations given in the 1987 edition to take account of developments in design and practice, and provides more detailed guidance in respect of care and maintenance As a code of practice, this British Standard takes the form of guidance and recommendations It should not be quoted as if it were a specification and particular care should be taken to ensure that claims of compliance are not misleading Tyre, wheel, rim and valve requirements are given in the following Parts and Sections of BS AU 50 — Part 1: Tyres; — Section 0: General; — Section 1: Car tyres; — Section 2: Commercial vehicle tyres; — Section 3: Off-the-road tyres; — Section 4: Agricultural tractor and machine tyres; — Section 5: Industrial vehicle tyres; — Section 6: Motorcycle tyres; — Section 7: Moped tyres; — Section 8: Code of practice for the storage of tyres, inner tubes and flaps — Part 2: Wheels and rims; — Section 0: General (including terms and definitions, and construction and workmanship); — Section 1: (Withdrawn); — Section 2: Specification for dimensions of wheel naves and hub centres for commercial vehicles; — Section 3: Specification for road-wheel nuts, studs, and bolts for commercial vehicles; — Section 5: Road wheels manufactured wholly or partly of cast light alloy for passenger cars; — Section 6: Specification for road wheels manufactured wholly or partly of light alloy for mopeds and motor cycles; — Section 7: Code of practice for the selection and care of wheels for commercial vehicles; — Section 8: Code of practice for the selection and care of wheels for passenger cars (including caravans and light trailers) — Part 3: Valves; — Section a: Specification for valve dimensions; — Section 2: Tyre valve threads 5V1, 5V2, 6V1 and 8V1; — Section 3: Tyre valve threads 9V1, 10V2, 12V1 and 13V1; — Section 4: Tyre valve threads 8V2, 10V1, 11V1, 13V2, 15V1, 16V1, 17V1, 17V2, 17V3, 19V1 and 20V1; — Section 5: Dimensions for ISO core chamber No for tyre inflation valves; — Section 6: Dimensions for ISO core chamber No for tyre inflation valves; — Section 7: Code of practice for the selection and care of tyre inflation valves for passenger cars (including caravans and light trailers); ii © BSI 03-1999 BS AU 50-2.7a:1995 — Section 8: Code of practice for the selection and care of tyre inflation valves for commercial vehicles — Part 4: Rim profiles and dimensions; — Section 1: Car rims ; — Section 2: Commercial vehicle rims; — Section 3: Off-the-road rims; — Section 4: Agricultural tractor and machine rims; — Section 5: Industrial vehicle rims; — Section 6: Motorcycle rims; — Section 7: Moped rims 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 to iv, pages to 20, 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 © BSI 03-1999 iii iv blank BS AU 50-2.7a:1995 7.1 Scope This Section of BS AU 50-2 gives recommendations on the steps to be taken in selecting replacement tyres and wheels for commercial vehicles and on the care of tyres, wheels and wheel fixings It describes the principal types of wheels and fixings and the procedures to be carried out when fitting wheels The types of fixings and sizes described in this standard are normally used on heavy commercial vehicles, but if used on other types of vehicle then the principles upon which the recommendations given in this standard are based also apply NOTE Recommendations for the selection and care of wheels for passenger cars and light trailers are given in BS AU 50-2.8 NOTE Attention is drawn to The Road Vehicles (Construction and Use) Regulations 1986 [1] as amended 7.2 References 7.2.1 Normative references This Section of BS AU 50 incorporates, by dated or undated reference, provisions from other publications These normative references are made at the appropriate places in the text and the cited publications are listed on the inside back cover For dated references, only the edition cited applies; any subsequent amendments to or revisions of the cited publication apply to this Section of BS AU 50 only when incorporated in the reference by amendment or revision For undated references, the latest edition of the cited publication applies, together with any amendments 7.2.2 Informative references This Section of BS AU 50 refers to other publications that provide information or guidance Editions of these publications current at the time of issue of this standard are listed on the inside back cover, but reference should be made to the latest editions 7.3 Tyre and wheel selection The initial choice of tyre and wheel combination and the arrangement at the particular wheel position is made by the vehicle manufacturer in accordance with published performance and application data Where a vehicle’s wheel and/or tyre specification is changed after manufacture e.g by body builders, operators, or specialist converters, this should be done in consultation with the vehicle manufacturer and having regard to the following factors: a) tyre/wheel load carrying capacity (design and legal restrictions); b) maximum speed of use; c) dimensional constraints e.g overall vehicle height, ground clearance, legal overall vehicle width, steering lock angle and suspension travel; © BSI 03-1999 d) compatibility with existing axles, hubs, brake assemblies and suspension; e) operation and service conditions; f) application of wheel/tyre assembly, e.g steered axle, drive axle, free rolling axle, or twin wheel NOTE Notes on tyre sidewall markings are given in Annex A Wheel types are described in more detail in Annex B 7.4 Tyre selection The tyre is the component which links the vehicle with the road surface under all conditions Its major functions which have a significant influence on the safety of the vehicle can be summarized as follows: — load carrying; — cushioning; — transmission of drive and braking forces; — steering and handling response Primarily, the tyre should be capable of carrying the maximum authorized load on the axle to which it is to be fitted at the vehicle’s legal maximum speed NOTE Any tyre chosen as a replacement should normally be of the same size, construction, and service description as the original equipment The vehicle and tyre manufacturers’ data should be consulted when a tyre other than that supplied as standard with the vehicle is to be used or if the application of the vehicle is likely to be changed A tyre is defined by the following: a) size designation comprising section width, aspect ratio and rim diameter; b) construction — normally radial but less frequently cross ply or bias belted; c) type of tread pattern according to individual manufacturer’s designation; d) service description — load index and speed symbol (see BS AU 50-1.2.1 and/or the ETRTO Standards manual [2] for details) NOTE Older tyres may not have a speed symbol and may carry a ply rating instead of a load index NOTE If any of these factors is to be altered, the suitability of the wheel for the amended tyre specification should also be verified and the factors listed in 7.3 a) to f) should be considered BS AU 50-2.7a:1995 7.5 Wheel selection 7.5.1 General The factors affecting wheel selection are those listed in 7.3 a) to f) Any wheel chosen as a replacement should be suitable for the application and normally of the same type, size, rim section, offset and fixing system as the original equipment Variations in the piercing or venting patterns in the wheel disc when mixed on one vehicle are permissible provided that access to the tyre valves on dual (twin) wheels is maintained and brake cooling is not impaired Any variation in wheel specification from the original should be verified with the vehicle manufacturer and/or the factors listed in 7.3 a) to f) checked When it is proposed to fit replacement wheels where the material type (e.g steel, cast iron, aluminium alloy), nave thickness or nave contour varies from the original, special consideration should be given to the suitability of the fixing system In particular, the following points should be checked: a) compatibility of the fixings see 7.6; b) stud length (where nave thickness has changed); c) clearance around brake, hub, and steering components; d) fitment and alignment of tyre valves on single and dual wheel arrangements; and e) half dual spacing or offset for the tyre size to give proper clearance when wheels are twinned or to maintain normal steering characteristics on steer axles NOTE For detailed descriptions of offsets see B.2 7.5.2 Wheel and rim designs Annex B lists the types of rims and wheels in general use and these are illustrated in Figure B.1 to Figure B.9 Annex C gives descriptions of the types of flanges and locking rings for use with the rims and wheels which are listed in Annex B, and cross-sections of typical flanges and locking rings are illustrated in Figure C.1 The endless flanges, spring flanges and locking rings for flat base, semi drop centre (SDC) and wide base rims illustrated in Figure C.1 are not interchangeable The correct size and type should always be used as serious accidents can result from the wrong application It is essential that endless flanges, spring flanges, locking rings and rims from different manufacturers are not intermixed When the tyre is fitted for inflation with the spring flange (two piece rim) or locking ring (three/four piece rim) in its correct position in the rim gutter, it is essential that the ends of the ring are not touching as this prevents correct seating WARNING It is emphasized that only the rim profiles are designated in BS AU 50-4.2.1 and the withdrawn BS AU 50-2.1 While the rim profiles and dimensions may appear suitable the wheel strength may not be and should be determined before use WARNING The use of replacement “dual purpose” wheels (see 7.6 ) is not recommended 7.5.3 Fitting of single wheels in place of twin wheels and the use of spacers Where single wheels are fitted as replacements for twin wheels, additional attention should be given to the wheel fixings If the original studs or bolts have plain shanks which are too long for the nuts to tighten on to the wheel or if the projecting length of the studs or bolts would adversely affect the fitting of socket spanners, it is recommended that suitable replacement studs or bolts are fitted (see paragraph of 7.7.4 ) If spacers are used to compensate for the absence of the inner wheel, such spacers should be of grades of steel or cast iron of a hardness not less than HV150 They should be accurately machined with an outside diameter not exceeding that of the wheel mounting face on the hub or brake drum and be free from sharp edges (See also BS AU 50-2.2.) The combined thickness of the spacer and the single wheel should be equal to the thickness of the original twin wheel assembly 7.6 Wheel fixings The majority of modern heavy commercial vehicles use spigot located wheels, where the wheel is centralized by the close fit of the wheel centre bore on the hub spigot With this type of mounting the wheel has plain stud holes and flat faced nuts with captive washers to clamp the wheel to the hub face Older United Kingdom vehicles (and some modern light commercial vehicles) have conical stud hole seatings that mate with the matching tapers of the wheel nuts both to centralize and support the wheel on the vehicle On dual (twin) wheels the inner wheel is centralized by and supported on a tapered collar or tapered split washer on the wheel stud shank © BSI 03-1999 BS AU 50-2.7a:1995 Older types of European commercial vehicles have a similar type of wheel mounting but the seating is spherical which is fundamentally different from the UK conical seating It is essential that these UK (BS conical seating) and European (DIN spherical seating) wheels are not in any circumstances interchanged even though it is physically possible and they appear to be compatible The conical and spherical components not mate together and if combined, loose wheels result It is vital to check that the wheel nuts and seatings are compatible to avoid incorrect matching Figure shows typical wheel fixings for conical seating, spherical seating and spigot mounting See BS AU 50-2.2 for dimensional details Wheels specifically designed for conical or spherical seating should never be used on hubs designed for spigot fixing Some replacement wheels have been produced which are designed to be used in a “dual purpose” mode The hub bore is dimensioned to suit spigot fixing but the stud holes are profiled to suit either DIN spherical or BS conical fixing nuts The use of these wheels is not recommended 7.7 Care and maintenance of wheels and tyres 7.7.1 General The care and maintenance of wheels, wheel fixings and tyres falls into three areas as follows: a) routine and special checks carried out by the driver(s) or other designated persons (see 7.7.2 ); b) periodic inspections by vehicle maintenance staff as part of the vehicle maintenance schedule (see 7.7.3 ); c) inspections by maintenance staff or specialist tyre fitters when tyres are changed or when wheels are removed for any other reason (see 7.7.4 ) If there are signs that a tyre has substantially deflated or has stood in a deflated condition, the tyre and/or wheel components may have become damaged or displaced The assembly should be removed from the vehicle and the tyre removed from the wheel The tyre should be examined to determine the reason for deflation and whether it is suitable for further service Each component part of the wheel should also be examined and replaced as necessary before being reassembled Any wheel found loose at inspection should be removed and the fixings, wheel and hub checked for wear and damage The wheel fitting procedure given in 7.8 should be followed when remounting © BSI 03-1999 7.7.2 Routine in-service checks During normal vehicle use tyres and wheels should be visually examined regularly (preferably at the start of each shift) Tyres should be examined for damage, abnormal or excessive wear, under-inflation and foreign objects embedded in them or trapped between dual (twin) tyres Wheels should be checked for signs of damage, cracks, distorted rims, displaced spring flanges or locking rings, broken or loose fittings and signs of wheel looseness e.g bright metal or rust marks in the area of nuts or captive washer seatings If looseness is suspected, the wheel nuts should be checked physically using the wheel nut wrench supplied with the vehicle by the vehicle manufacturer, or a socket and short bar of corresponding length Any defects, including loose wheel nuts, should be reported immediately and the vehicle should not be driven further without clear authority If wheel fixings are loose, there is a reason The wheel should be removed and all relevant components examined as soon as practicable WARNING Retightening loose wheel nuts on the road (or anywhere else) without first ascertaining the reason for looseness and the extent of any wear or damage is potentially dangerous Overtightening of wheel fixings (e.g by using extension bars) can result in damage to fixings, wheels and hubs, the subsequent failure of which can result in wheel loss 7.7.3 Periodic maintenance inspections These inspections should be carried out regularly in accordance with the preventative maintenance schedule issued by the vehicle manufacturer which should incorporate the items listed in 7.7.2 but in greater depth, e.g tyre pressure should be checked and adjusted as necessary to the correct value Figure — Wheel fixings BS AU 50-2.7a:1995 © BSI 03-1999 BS AU 50-2.7a:1995 Figure — Sequence of stud tightening © BSI 03-1999 BS AU 50-2.7a:1995 Annex A (informative) Bus and truck tyre sidewall markings Sidewall markings used on truck and bus tyres are shown in Figure A.1 As shown in Figure A.1, nearly all truck tyres are now marked with a service description made up of the following two components a) Load index One or two numbers which indicate the load the tyre can carry in a single or in a single and dual formation at the speed corresponding to the associated speed symbol b) Speed symbol A letter or a letter and a number which indicate the speed at which the tyre can carry the load corresponding to the associated load index The loads corresponding to the load index values are listed in Table A.1 and the speeds corresponding to the speed symbols are listed in Table A.2 NOTE On some tyres a second service description is marked This is a unique point and provides an additional rating at the specific conditions of load and speed indicated Unlike the basic service description it cannot be used as the basis for calculating bonus loads at reduced speeds or higher speeds at reduced loads NOTE Some older tyres may carry a ply rating (PR) symbol as an indication of tyre strength Figure A.1 — Bus and truck tyre sidewall markings © BSI 03-1999 BS AU 50-2.7a:1995 Table A.1 — Load index values Load index Load Load index Load Load index Load Load index Load (LI) kg (LI) kg (LI) kg (LI) kg 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 335 345 355 365 375 387 400 412 425 437 450 462 475 487 500 515 530 545 560 580 600 615 630 650 670 690 710 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 1 1 1 1 1 1 1 1 730 750 775 800 825 850 875 900 925 950 975 000 030 060 090 120 150 180 215 250 285 320 360 400 450 500 550 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 600 650 700 750 800 850 900 950 000 060 120 180 240 300 360 430 500 575 650 725 800 900 000 075 150 250 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 350 450 550 650 750 875 000 125 250 375 500 625 750 875 000 150 300 450 600 800 000 150 300 500 700 900 Table A.2 — Speed symbol values Symbol Speed km/h F G J K L M N P Q R S 10 80 90 100 110 120 130 140 150 160 170 180 mile/h (approx.) 50 56 62 68 75 81 87 93 100 106 113 © BSI 03-1999 BS AU 50-2.7a:1995 Annex B (informative) Types of rims and wheels B.1 Rims B.1.1 General There are six types of rims in general use on commercial vehicles in the UK as follows: a) wide base rims (see Figure B.1); b) flat base rims (see Figure B.2); c) semi drop centre (SDC) rims (see Figure B.3); d) drop centre rims (see Figure B.4); e) well base rims (see Figure B.5); f) divided rims (see Figure B.6) These rims can be made in a number of pieces as follows: 1) one-piece rim: a rim base having no detachable parts; 2) two-piece rim: a rim base with one detachable spring flange; 3) three-piece rim: A rim base with one detachable endless flange and one spring locking ring; 4) four-piece rim: a rim base with two detachable endless flanges and one spring locking ring; 5) two-piece divided rim: a rim having two main parts bolted together NOTE See BS AU 50-4.2.1 for details of metric rim profiles and the withdrawn standard BS AU 50-2.1 for details of other profiles, as appropriate B.1.2 Wide base rims (see Figure B.1) Wide base rims have a 5° taper bead seat and are available in two-piece or three-piece construction as shown in Figure B.1 a) and Figure B.1 b), respectively The letter “B” in the size designation is used to distinguish them from the flat base rims and the profile is in accordance with 1.6.3 of the withdrawn standard BS AU 50-2.1:1980, e.g 20-B6.5 In Figure B.1 the nominal rim width codes 2) (code 6.0 in Figure B.1 a) and code 6.5 in Figure B.1 b) refer to the width between the flanges The nominal diameter code2) [code 20 in Figure B.1 a) and Figure B.1 b)] refers to the diameter of the rim B.1.3 Flat base rims (see Figure B.2) Flat base rims, as the name indicates, have a flat rim base (not tapered) and are available in two-piece, three-piece or four-piece construction as shown in Figure B.2 a), Figure B.2 b) and Figure B.2 c), respectively This type of rim has been largely superseded by the wide base rims described in B.1.2 A typical size of flat base rim is shown in Figure B.2 b) (20-6.00T) In Figure B.2 the nominal rim width codes 2) [code 3.75 in Figure B.2 a)], code 6.00 in Figure B.2 b) and code 10.00 in Figure B.2 c) refer to the width between the flanges The nominal diameter codes 2) [code 13 in Figure B.2 a) and code 20 in Figure B.2 b) and Figure B.2 c)] refer to the diameter of the rim The letter in the size designation e.g “T”, “P” or “W” is a reference code for the height of the rim flange B.1.4 Semi drop centre (SDC) rims (see Figure B.3) SDC rims have a shallow well in the rim base to facilitate the fitting and removal of the tyre They are normally manufactured as part of nominal diameter code 16 2) wheels and have 5° tapered bead seats and are suitable for light commercial vehicles SDC rims are available in a two-piece or three-piece construction as shown in Figure B.3 a) and Figure B.3 b), respectively A typical size of SDC rim is shown in Figure B.3 a) (16-6.00G) In Figure B.3 the nominal rim width code 2) (code 6.00) refers to the width between the flanges The nominal diameter code2) (code 16) refers to the diameter of the rim The letter “G” is a reference code for the height of the rim flange B.1.5 15° drop centre rims (see Figure B.4) Drop centre rims have a deep well and low flanges to facilitate the fitting and removal of the tyre The bead seats have a 15° taper to ensure concentricity of the tyre fitting and an airtight seal Drop centre rims are manufactured as one piece rims for use with tubeless tyres as shown in Figure B.4 a) and Figure B.4 b) A typical size of drop centre rim is shown in Figure B.4 a) (22.5 × 7.50) In Figure B.4 the nominal rim width codes 2) [code 7.50 in Figure B.4 a) and code 14.00 in Figure B.4 b)] refer to the width between the flanges The nominal diameter code2) [code 22.5 in Figure B.4 a) and Figure B.4 b)] refers to the diameter of the rim 2) The sizes indicated by these codes are specified precisely in BS AU 50-2.1 (withdrawn) and BS AU 50-4.2.1 The codes give an approximation of the specified dimension in inches © BSI 03-1999 11 BS AU 50-2.7a:1995 B.1.6 5° well base rims (see Figure B.5) Some light commercial vehicles are fitted with one-piece 5° well base rims, which are similar in design to a car rim and have 5° bead seats and a rim well to facilitate the fitting and removal of the tyre A typical size of well base is shown in Figure B.5 (14 × 5J) In Figure B.5 the nominal rim width code3) (code 5) refers to the width between the flanges The nominal diameter code3) (code 14) refers to the diameter of the rim The letter “J” is a reference code for the height of the flange of the rim Figure B.1 — Wide base rims 3) The sizes indicated by these codes are specified precisely in BS AU 50-2.1 (withdrawn) and BS AU 50-4.2.1 The codes give an approximation of the specified dimension in inches 12 © BSI 03-1999 BS AU 50-2.7a:1995 Figure B.2 — Flat base rims © BSI 03-1999 13 BS AU 50-2.7a:1995 Figure B.3 — Semi drop centre (SDC) rims 14 © BSI 03-1999 BS AU 50-2.7a:1995 Figure B.4 — 15° drop centre rims Figure B.5 — 5° well base rim © BSI 03-1999 15 BS AU 50-2.7a:1995 Figure B.6 — Divided rim B.1.7 Divided rims (see Figure B.6) In this design the rim is made in two main parts which are bolted together (or fastened by an equivalent mechanical method) to form a wheel This type of wheel is fitted to commercial vehicles, industrial trucks and some military vehicles Earlier rim contour designs were of the flat base type, but it is currently more usual to incorporate a 5° taper bead seat A typical size of divided rim is shown in Figure B.6 (8-4.33R) In Figure B.6 the nominal rim width code 4) (code 4.33) refers to the width between the flanges The nominal diameter code4) (code 8) refers to the diameter of the rim The letter “R” is a reference code for the height of the flange of the rim B.2 Wheels B.2.1 General In the UK the wheels fitted to commercial vehicles are disc type wheels These may be cast or forged in one piece and made from a variety of materials, but the commonest form of construction is that of a pressed steel disc welded to a rolled steel rim It should be noted that multi-piece rims are usually attached to the disc so that the locking flange or locking ring faces outwards in single wheel applications In the case of 15° drop centre rims for tubeless tyres, the rim may be attached to the disc so that the well is offset to the outside of the wheel (earlier “A” type wheel), or to the inside of the wheel (later “U” or underledge type wheel), in single wheel configuration There are differences in the valve arrangement and in the details of tyre fitting procedure between the two types (see Figure B.7) The position of the disc attachment face relative to the centre line of the rim is called offset Typical examples are shown in Figure B.8 and Figure B.9 B.2.2 Single wheel offset Single wheel offset is positive when the centre line of the rim in inboard of the attachment face of the disc and is called inset [see Figure B.8 a)] Offset is zero when the centre line of the rim is coincident with the attachment face of the disc [see Figure B.8 b)] Offset is negative when the centre line of the rim is outboard of the attachment face of the disc and is called outset [see Figure B.8 c)] B.2.3 Dual (twin) wheel offset or half dual spacing (see Figure B.9) The offset of dual (twin) wheels, also called “half dual spacing”, is the distance S from the centre line of the rim to the outer face of the wheel disc and is calculated from the equation: S = A — B/2 where A and B are the dimensions indicated in Figure B.9 4) The sizes indicated by these codes are specified precisely in BS AU 50-2.1 (withdrawn) and BS AU 50-4.2.1 The codes give an approximation of the specified dimension in inches 16 © BSI 03-1999 BS AU 50-2.7a:1995 Figure B.7 — Earlier and later types of tubeless wheels © BSI 03-1999 17 BS AU 50-2.7a:1995 Figure B.8 — Single wheel offset Figure B.9 — Dual (twin) wheel offset or half dual spacing 18 © BSI 03-1999 BS AU 50-2.7a:1995 Annex C (informative) Types of flanges, spring flanges and locking rings C.1 Flanges for two-piece rim wheels On two-piece rim wheels spring flanges are fitted to the side of the rim containing a groove (known as a gutter groove) and are fitted into position using levers To enable the spring flange to be fitted into the gutter groove the flange is split No locking ring is used C.2 Flanges for three-piece and four-piece rim wheels On three-piece and four-piece rim wheels endless flanges and locking rings are always used together and are fitted into position using levers The flange is not split, but the locking rim is split to enable it to be sprung into the gutter of the rim On four-piece flat base rims two endless flanges are required C.3 Conversion of two-piece rims into three-piece rims All two-piece wide base rims and SDC rims may be converted into three-piece rims by substituting an endless flange and locking ring, of the correct size, make and type, in place of the spring flange C.4 Typical flanges and locking rings Cross-sections of typical flanges and locking rings for use with wide base rims, flat base rims and SDC rims are illustrated in Figure C.1 © BSI 03-1999 19 BS AU 50-2.7a:1995 Figure C.1 — Cross-sections of typical flanges and locking rings 20 © BSI 03-1999 BS AU 50-2.7a:1995 List of references (see 7.2 ) Normative references BSI publications BRITISH STANDARDS INSTITUTION, London BS AU 50, Tyres and wheels BS AU 50-2, Wheels and rims BS AU 50-2.0a:1979, General (including terms and definitions, and construction and workmanship) BS AU 50-3:1994, Specification for road-wheel nuts, studs and bolts for commercial vehicles Other references [3] HEALTH AND SAFETY EXECUTIVE Health and safety in tyre and exhaust fitting premises HSG62, 1991 5) Informative references BSI publications BRITISH STANDARDS INSTITUTION, London BS AU 50, Tyres and wheels BS AU 50-1, Tyres BS AU 50-1.2, Commercial vehicle tyres BS AU 50-1.2.1:1991, Specification for sizes, loads inflation pressures and rims for commercial vehicle tyres BS AU 50-2, Wheel and rims BS AU 50-2.1b:1980, Rim profiles and dimensions (including openings for valves)6) BS AU 50-2.2:1984, Specification for dimensions of wheel naves and hub centres for commercial vehicles BS AU 50-2.8a:1985, Code of practice for the selection and care of wheels for passenger cars (including caravans and light trailers) BS AU 50-4, Rim profiles and dimensions BS AU 50-4.2, Commercial vehicle rims BS AU 50-4.2.1:1995, Specification for metric series rims Other references [1] GREAT BRITAIN Road Vehicles (Construction and Use) Regulations 1986 London: HMSO [2] ETRTO Standards manual (published anually) 7) 5) Available from HMSO 6) This Section of BS AU 50 was withdrawn in 1995 However, it contains information of relevance to older vehicles 7) Available from the European Tyre and Rim Technical Organization, 32 Avenue Brugmann, 1060 Brussels, Belgium © BSI 03-1999 BSI 389 Chiswick High Road London W4 4AL || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || | BSI Ð British Standards Institution BSI is the independent national body responsible for preparing British Standards It presents the UK view on standards in Europe and at the international level It is incorporated by Royal Charter Revisions British Standards are updated by amendment or revision Users of British Standards should make sure that they possess the latest amendments or editions It 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