arp007

ARP007

(As amended)

Edition 21992

ICS 43.040.50; 83.160.10

ISBN 0-626-13344-0

SOUTH AFRICAN BUREAU OF STANDARDS

Recommended practice

The care, maintenance and use of motorvehicle tyres and rims (incorporating TREDCOguidelines)

Reprint 1994Published byTHE SOUTH AFRICAN BUREAU OF STANDARDS

This standard may only be used by approved subscription and freemailing clients of the SABS.

ARP 007Ed. 2


ICS 43.040.50; 83.160.10 ARP 007Ed. 2

SOUTH AFRICAN BUREAU OF STANDARDS

RECOMMENDED PRACTICE

THE CARE, MAINTENANCE AND USE OF MOTOR VEHICLETYRES AND RIMS (incorporating TREDCO guidelines)

Obtainable from the

South African Bureau of StandardsPrivate Bag X191PretoriaRepublic of South Africa0001

Telephone : (012) 428-7911Fax : (012) 344-1568E-mail : [email protected] : http://www.sabs.co.za

COPYRIGHT RESERVED

Printed in the Republic of South Africa by theSouth African Bureau of Standards


ARP 007Ed. 2

ii

Acknowledgement to TREDCO

The SABS acknowledges the services of the Tyre and Rim Engineering Data Committee of South Africa(TREDCO), whose members are listed below, in providing the information for inclusion in thisrecommended practice.

Dunlop Tyres (Pty) Ltd - Dunlop and India tyres

Firestone South Africa (Pty) Ltd - Firestone tyres

Guestro Wheels - vehicle rims

National Association of Automobile Manufacturers of South Africa (NAAMSA)

South African Bureau of Standards (SABS)

The General Tyre and Rubber Company (South Africa) (Pty) Ltd - General and Continental tyres

Tycon (Pty) Ltd - Goodyear and Kelly tyres

TREDCO was established in the early nineteen sixties as an advisory body to the South African tyre andautomobile industries, and the first edition of Tyre and rim engineering data (also known as the TREDCOdata manual and the TREDCO data book) was published in 1968 and replaced the Year book originallypublished by the South African Tyre Manufacturers' Conference (SATMC).

TREDCO acknowledges the valuable assistance derived from publications of the following organizations:

ETRTO European Tyre and Rim Technical Organisation

SMM&T The Society of Motor Manufacturers and Traders Limited of Great Britain

TAC The Technical Advisory Committee to the South African Tyre Manufacturers'Conference

T&RA The Tyre and Rim Association Inc. of the United States of America

Reprint incorporating Amendment No. 1 : 5 July 1994

ISBN 0-626-13344-0


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Notice

This recommended practice was approved by the Director General of the South African Bureau ofStandards on 15 June 1992.

The document consists of a set of recommendations intended to facilitate the execution of a particularoperation and has been produced by the SABS in conjunction with the Tyre and Rim Engineering DataCommittee of South Africa (TREDCO). It does not fall within the scope of section 33 of the StandardsAct, 1982 (Act 30 of 1982).

Authorities who wish to incorporate any part of this recommended practice into any legislation shouldconsult the South African Bureau of Standards regarding the implications.

This recommended practice will be revised when necessary. Comment will be welcomed and will beconsidered when the document is revised.

Foreword

This recommended practice is intended to be used as a supplement to SABS 1550:1992, Motor vehicletyres and rims - Dimensions and loads.

This first revision cancels and replaces ARP 007:1989, which replaced the TREDCO guidelines in theTREDCO data manual.

Introduction

The purpose of this recommended practice is to promote an understanding of the practices relevant tothe safe care, maintenance and use of motor vehicle tyres and rims, particularly with respect to theload-carrying capacities of such tyres and rims.

TREDCO advises that in determining the load-carrying capacity of a tyre, three factors should be takeninto consideration, namely

- the volume of air contained in a tyre,

- the pressure of air contained in a tyre, and

- the load factor.

The size of the tyre determines the volume of air, and the ply rating determines the maximum pressureunder which the air can safely be retained in the tyre.

The load factor varies from country to country according to the service conditions of the tyre, and mayvary within one country according to road conditions, ambient temperature, traffic density, number ofvehicle occupants, and other factors.

Load factors which are in use in most countries have been established over the years by monitoring theservice performance of many tyres of different manufacturers. Load factors are therefore a compromise,giving the optimum value for the whole country, but still ensuring that safety considerations are notneglected.

Load factors are continually reviewed as road conditions vary; therefore amendments to thisrecommended practice will be issued from time to time.

All TREDCO engineering data of general interest are included in this recommended practice. Certainother information, however, has a very limited field of interest and is therefore published in theExperimental and Permissible Practices Journal. This journal has a limited distribution and is not freelyavailable. Enquiries regarding tyre load, rim profiles and uses not appearing in this recommendedpractice can be directed to the Chairman of TREDCO or to the individual tyre manufacturers.


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Contents

Page

Acknowledgement to TREDCO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii

Notice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

Committee . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

3 Recommended practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3.1 Tyre types, sizes and selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53.2 Tyre inflation pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83.3 Tyre condition and usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93.4 Fitment and replacement of tyres, tubes and valves . . . . . . . . . . . . . . . . . . . . . . . . . . . 153.5 Tyre and rim damage and maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163.6 Mismatched rim and wheel parts of particular importance on commercial vehicles . . . 19

Figures 1 to 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-24


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Committee

South African Bureau of Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IB Charlton*(Chairman)G Kinsey*(Standards writer)H Patrick(Committee clerk)

Automobile Association of South Africa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . J van Vreden

BMW (South Africa) (Pty) Ltd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . K Schmelzer

City Council of Pretoria City Transport Department . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FD Rossouw

Dunlop Tyres (Pty) Ltd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G Shaw*

Firestone South Africa (Pty) Ltd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . J Barnard*E van Zyl*

Guestro Wheels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D Twigg*

Mercedes-Benz of South Africa (Pty) Ltd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M BatailleHJ de Bruyn

National Association of Automobile Manufacturers of South Africa (NAAMSA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . J Nimmo*

CAZ Pierides

The General Tyre and Rubber Company (South Africa) (Pty) Ltd . . . . . . . . . . . . S Coetzee*P Swart*

Transvaal Provincial Administration Roads Department . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CJ Jacobs

Tycon (Pty) Ltd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D Manefeldt*K Stevens*

Volkswagen SA (Pty) Ltd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . J Summersell

NOTE - "*" denotes the members of the Tyre and Rim Engineering Data Committee (TREDCO) who served as thesubcommittee which was responsible for drafting this recommended practice.


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Blank


1

The care, maintenance and use of motorvehicle tyres and rims

(incorporating TREDCO guidelines)


2

RECOMMENDED PRACTICE ARP 007Edition 2

The care, maintenance and use of motor vehicle tyres and rims(incorporating TREDCO guidelines)

1 Scope

This recommended practice sets out practices relevant to the care, maintenance and use of motorvehicle tyres and rims.

2 Definitions

NOTE - The definitions are listed in alphabetical order.

For the purposes of this recommended practice, the following definitions apply:

2.1 aircraft tyre: A tyre designed for use on aircraft. The parameters affecting the design and selectionof aircraft tyres are entirely different from those used for other types of tyre. Owing to mass and sizelimitations, aircraft tyres are designed to carry high loads at very high speeds for periods of limitedduration. The materials used in their construction and the tread patterns employed, render them suitablefor aircraft use only; in addition, they are designed to fit tapered bead seats which are machined to a highdegree of accuracy.

2.2 aspect ratio: The ratio of the section height to the section width of the tyre.

2.3 basic pressure: The inflation pressure which, for a particular load, would (under optimumconditions) give the longest tyre life.

2.4 bead: The portion of a tyre that is of such shape as to fit the rim and to hold the tyre on it (seefigure 1).

2.5 belt: The layer of material underneath the tread of a tyre and that, in the case of radial-ply tyres,is laid substantially in the direction of the tread centre-line, and that constrains the tyre carcass in acircumferential direction.

2.6 carcass: The portion of a tyre, excluding the protective tread and sidewalls (see figure 1).

2.7 cord: The threads used in the construction of the various components of the tyre carcass such asplies, belts and breakers (see figure 1).

2.8 diagonal-ply tyre: A pneumatic tyre in which the ply cords extend to the beads and are laid atalternate angles that are substantially less than 90° to the tread centre-line. A diagonal-ply tyre may alsobe referred to as a cross-ply or a bias-ply tyre.


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2.9 driveaway vehicle: An unloaded off-the-road or commercial vehicle being driven over a pavedhighway during the delivery cycle or during site-to-site transfer.

2.10 front-end loader: A tractor chassis that has a power-operated lifting mechanism with a bucketor similar container mounted at the front of the tractor.

2.11 grown tyre: A tyre that has undergone expansion due to continued service use.

2.12 grown tyre overall diameter: The maximum overall diameter of an inflated tyre, including servicegrowth.

2.13 grown tyre overall width: The maximum overall width of an inflated tyre, including servicegrowth.

2.14 hillside combine: An agricultural vehicle intended for service on a slope with a gradientexceeding 20 %.

2.15 inflation growth: The natural expansion of a tyre that has been inflated to a specified inflationpressure, allowed to stand at ambient room temperature for at least 24 h, and then re-inflated to thesame specified inflation pressure.

2.16 inflation pressure: The pressure in a tyre that has not been subjected to an increase of pressuredue to the heat of vehicle operation (a cold tyre), which is measured at the prevailing atmospherictemperature, and which can be equated to a maximum tyre load capability.

2.17 light truck tyre: Any tyre that has a rim diameter not exceeding code 16 or, in the case of a 15°tapered drop-centre rim, code 17,5 and that is designed to fit a drop-centre or semi-drop-centre rim ona light commercial vehicle.

2.18 main grooves (on a tyre tread pattern): The deepest grooves across the road contact area of thetyre. The depth of a main groove is determined by design standards for particular tyre sizes andapplications. Main grooves can run radially or circumferentially (or both) over the tread pattern(see figure 1).

2.19 measuring rim: The size of rim upon which a tyre is required to be mounted for the purpose ofsize measurement.

2.20 motor racing tyre: A tyre specifically designed for vehicles used in motor racing on motor racecircuits. Such tyres have certain dimensions, shapes, tread patterns and compounds, which make themsuitable for motor racing purposes only. The tread components and patterns are usually of a "dry" or"wet" use type and should only be used under these conditions.

2.21 new tyre: A tyre that has neither been used nor been subjected to any retreading operation.

2.22 NHS: Markings on an industrial vehicle tyre that indicate restricted industrial use and denote NOTFOR HIGHWAY SERVICE.

2.23 nominal aspect ratio: One hundred times the ratio of the section height to the nominal sectionwidth, both dimensions being expressed in the same units. For tyre classification purposes, the nominalaspect ratio is treated as approximate only.

2.24 nominal rim diameter: The diameter of a rim upon which the tyre is designed to be mounted(see figure 1).


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2.25 nominal section width: The section width of a tyre mounted on the theoretical rim designatedby the tyre manufacturer.

2.26 overall diameter: The maximum diameter of an inflated new tyre, after inflation growth, measuredat the outermost surface of the tread (see figure 1).

2.27 overall width: The maximum width, measured between the outside sidewalls of an inflated newtyre, after inflation growth, that includes the largest protrusions due to markings, decorations, protectiveside ribs and bars.

2.28 passenger-carrying commercial vehicle: A commercial vehicle that is primarily designed forthe carriage of passengers and that includes any bus, school bus, bus-train, minibus or a semi-trailerused for passengers.

2.29 permitted rim: Any rim, in addition to the specified rim, whose fitment to a specified tyre ispermitted.

2.30 ply: A layer of rubber-coated parallel cords (see figure 1).

2.31 ply rating: A numeric index used to identify a given tyre with its maximum recommended loadwhen the tyre is used in a specific type of service. The rating does not necessarily represent the actualnumber of plies in a tyre.

2.32 radial-ply tyre: A pneumatic tyre in which the ply cords extend to the beads and are laidsubstantially at 90° to the tread centre-line, the carcass being stabilized by a circumferential beltconsisting of two or more layers of essentially inextensible cord material.

2.33 section height: A distance equal to half the difference between the overall diameter of the tyreand the nominal rim diameter (see figure 1).

2.34 section width: The width measured between the outside sidewalls of an inflated new tyre, afterinflation growth, but that excludes any protrusions due to markings, decorations, protective side ribs andbars (see figure 1).

2.35 sidewall: That portion of the tyre between the tread and the bead (see figure 1).

2.36 SL: Markings on an agricultural vehicle tyre that indicate restricted agricultural use and denoteSERVICE LIMITED.

2.37 spare wheel: A wheel assembly, carried as a spare, that conforms to and is identifiable with thewheel assembly specified for the vehicle. Such a spare wheel unit could be of restricted fitmentdepending on whether differing wheel sizes are specified for front or rear use on the vehicle.

2.38 specified rim: The rim, or rims, that give(s) the best fitment of the tyre for all conditions andservice.

2.39 speed rating symbol: An alphabetical character used to identify (rate) the highest safe speed atwhich the tyre/rim combination can carry its maximum load under service conditions as specified by themanufacturer.


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2.40 temporary-use spare wheel: A wheel assembly, carried as a spare, that differs from a normalspare wheel with regard to the principal characteristics (e.g. size designation, functional dimensions,conditions of use or structure). It is intended for temporary use under restricted operating conditions.

2.41 theoretical rim: A rim whose width is equal to x times the nominal section width of a tyre; thevalue of x is specified by the manufacturer of the tyre.

2.42 tiebar: An aesthetic and functional design feature used in tyre tread design. The purpose of thetiebar is to link two of the tread blocks or ribs, thereby aesthetically enhancing the look of the treadpattern or functionally supporting the tread for overall stability in that area. Tiebars can either be fullgroove height or part thereof (see figure 5).

2.43 tread: The portion of the tyre that is normally in contact with the ground, that contributes to groundadhesion, and that protects the carcass from mechanical damage (see figure 1).

2.44 tread-wear indicators: Raised protrusions located within the main grooves of the tyre treadpattern, which indicate the amount of tread pattern depth, i.e. non-skid depth (NSD) remaining acrossthe tyre tread surface. These indicators are spaced uniformly around the tyre circumference andapproximately across the full tread width in all the main grooves (see figure 4).

2.45 wheel: The combination of a wheel disc plus the rim.

2.46 wheel assembly: The combination of a wheel disc plus the rim (the wheel), with the tyre and itsinner tube, if applicable, installed thereon.

3 Recommended practices

3.1 Tyre types, sizes and selection

3.1.1 Type of construction

In order to avoid incompatibility problems on a vehicle, tyres other than diagonal-ply are clearly identified.Similarly, tyres of tubeless construction are clearly marked as tubeless.

3.1.2 Tyre size designation

The designation of a tyre includes the nominal section width and the nominal rim diameter and, whereapplicable, the nominal aspect ratio and the speed category rating.

The tyre designation should be such that the load-carrying capacity of the tyre can be readily identifiedby reference to the tables given in SABS 1550.

Diagonal-ply tyres of 6-ply rating or greater are marked with the relevant ply rating, and passenger cartyres not marked with any rating should always be taken as 4-ply.

Commercial vehicle tyres may be identified by the initial `C' adjacent to the tyre designation marking.

Tyres of radial-ply construction shall be clearly marked 'R' and, optionally, 'RADIAL'. In addition, the tyremay be marked with the word 'STRAAL'. Reinforced tyres shall bear the marking 'REINFORCED'. Inaddition, the tyre may be marked with the word 'VERSTERK'. Tubeless tyres shall be marked'TUBELESS'. In addition, the tyre may be marked with the word 'BINNEBANDLOOS'.

Special tyres designed for temporary use only have additional markings in at least one of the officiallanguages, identifying any particular restrictions regarding their use.


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3.1.3 Section width

The section width, when the tyre is fitted to the measuring rim, may be obtained by means of thefollowing formula:

S = S1 + K(A-A1)

where

S is the section width, in millimetres;

S1 is the nominal section width, in millimetres, as marked on the sidewall of the tyre in the tyredesignation;

A is the width of the measuring rim, in millimetres, as given by the manufacturer;

A1 is the width of the theoretical rim, in millimetres (equal to S1 multiplied by a factor x as specifiedby the manufacturer); and

K is a constant which is normally taken to equal 0,4.

For existing tyres, the dimensions specified in the relevant tables of SABS 1550 should be used.

3.1.4 Overall diameter

The overall diameter of a tyre may be obtained by means of the following formula:

D = d + 0,02 (S1 . Ra)

where

D is the overall diameter, in millimetres;

d is the nominal rim diameter, in millimetres;

S1 is the nominal section width, in millimetres; and

Ra is the nominal aspect ratio, expressed as a percentage.

For existing tyres, the dimensions specified in the relevant tables of SABS 1550 should be used.

3.1.5 Tyre measurement

The measurement procedure is carried out at ambient room temperature without any load on the tyre,and the tyre used shall be a new one that has not previously been inflated. All the sectional dimensionsand overall diameters given refer to such tyre measurements.


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3.1.6 Tyre and rim selection for vehicle design purposes

For vehicle design purposes, the specified rims should preferably be selected. In the case of passengercar tyres, if a different rim is selected, the section width will change 5 mm for each ½ rim width codenumber or 12,5 mm change in rim width from that specified for the measuring rim. It should also be notedthat the inflation pressures on a vehicle may differ subject to agreement between the tyre manufacturerand the vehicle manufacturer. Account should not only be taken of the tyre load-carrying capacity butalso of the operating conditions, the maximum speed, the position of the tyre on the vehicle, serviceconditions and the construction and characteristics of the vehicle. In particular, for higher speeds,increases in pressure are essential and a reduction in the tyre load-carrying capacity may also berequired.

3.1.6.1 Passenger cars

In the case of passenger cars, the maximum load on each individual wheel based on the mass per axleshould be taken into account.

The mass of the passenger car for determining the load on a tyre should be made up of the greater ofeither the gross vehicle mass (GVM), or the combined mass of the front and rear gross axle massloads,both as given by the manufacturer of the vehicle.

NOTE - In the majority of modern passenger cars, the combined gross axle massloads exceed the stated GVM and thereforethe tyres selected for particular axles should be capable of supporting the manufacturer's gross mass loadings.

3.1.6.2 Caravans and light trailers

In the case of caravans and light trailers, the maximum load on each individual wheel should be basedon the gross vehicle mass of the vehicle, fully equipped or loaded. The caravan GVM should include anallowance for household, personal and miscellaneous equipment carried. The total mass of the caravanor light trailer should be used, and no allowance should be made for any proportion of the mass carriedby a towing vehicle.

3.1.6.3 Commercial vehicles and buses

In the case of commercial vehicles, the maximum load on each individual wheel is determined by thevehicle manufacturer or the body manufacturer of the completed vehicle, and the choice of tyre size andply rating on each axle should be based on the highest individual wheel load.

The maximum load per tyre should not exceed the applicable load specified for the relevant category tyrefor the correct ply rating and usage.

3.1.6.4 Motorcycles and motor scooters

The basic tread configurations consist of four types that are normally adopted for the service given asfollows:

- type A, normal highway service;

- type B, special high-speed service;

- type C, on-road and off-the-road service; and

- type D, off-the-road service only.


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The attribution of tread configurations to a type of service is to be considered only by way of an example.The choice of a given tread configuration for a given tyre depends on the tyre manufacturer only.

Types A, B, C and D tread configurations are shown in figure 2.

3.1.6.5 Off-the-road vehicles

Selection of size and ply rating on each axle is based on the highest individual wheel load (determinedby the GVM distribution, including load transfer).

The maximum load per tyre should not be greater than specified in applicable tables.

For haulage vehicle design, the following maximum inflation pressures are recommended:

- wide base: 380 kPa; and

- conventional: 490 kPa.

3.1.6.6 Agricultural vehicles

Selection of size and ply rating on each axle is based on the highest individual wheel load (determinedby GVM distribution).

GVM includes the mass of all necessary items, operational equipment, tyre ballast, and payload, andshould take into account any effects of field modifications.

For sustained high torque service, drive wheel tyres on agricultural tractors operating in the field shouldbe selected to withstand the maximum pull of the tractor under normal operating service.

The tangential pull value of a tyre is the maximum horizontal pull the tyre can continuously withstandexcluding momentary and occasional peak loads. The maximum tangential pull capability of the tyre isshown in the appropriate tables in SABS 1550. These values are to be used for vehicle design, includingfield modifications.

3.2 Tyre inflation pressure

The tyre inflation pressure is one of the major factors in the road-holding characteristics of a vehicle andadditionally, most tyre damage is due to, or aggravated by, incorrect inflation pressures.

3.2.1 Basic pressure

The inflation pressures quoted in SABS 1550 for the specific tyre loadings represent the basic inflationpressures of the tyres.

The pressures used in practice for the tyres on the vehicle may be different and are fixed by agreementbetween the tyre manufacturer and the vehicle manufacturer. They should take into account not only theload but also the tyre construction, the road holding, the maximum recommended safe speed, thelocation of the tyre, the operating conditions and the mechanical characteristics of the vehicle. Alwaysrefer to the vehicle manufacturer's handbook.


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3.2.2 Pressure checking

Pressure checks should be conducted at regular two-weekly intervals, or before any long journey;accurate pressure gauges should be used and the tyres should be cold. The tyres should be re-inflatedas necessary to maintain the correct inflation pressures. The spare tyre should also be included in thecheck.

3.2.3 Normal pressure increase

Tyre pressure increase (up to 20 % or more) is a normal phenomenon during operation of the tyre, andthe design of a tyre allows for such an increase. After sustained operation, hot tyres should never bereadjusted to the pressure recommended for cold tyres.

3.2.4 Sustained high speed

If sustained high speed is anticipated, an increase in tyre inflation pressure prior to such operation isessential. Consult the vehicle manufacturer's handbook.

3.2.5 Pressure distribution

All tyres on the same axle should be maintained at the same pressure.

3.2.6 Dust caps

The valve dust cap, which acts as a dust seal, should be kept correctly fitted at all times.

NOTE - Dust caps may be of the plastics type or of the metal type incorporating a rubber seal. Metal type caps arerecommended for truck tyres.

3.2.7 Underinflation

Driving with underinflated tyres should be avoided. In the case of multi-axle or twin axle vehicles, thedriver may not always be aware of an underinflated (or flat) tyre.

NOTE - Some commercial vehicles provide warning devices for such contingencies.

3.3 Tyre condition and usage

3.3.1 General

The tread of a tyre is provided with a grooved pattern, the purpose of which is to ensure the best grip ofthe tyre on a road surface.

3.3.1.1 Road holding

The tread pattern alone does not ensure a tyre grip under given load and inflation pressure conditions.In addition to the tread pattern itself, other features such as tyre construction, chemical composition ofthe tread, differing road surfaces (cement, asphalt, tarred, smooth, rough, etc.), differing climaticconditions (dry, wet, waterlogged, icy, etc.), mechanical features of the vehicle, the driver's experienceand style and, most important, driving speed, are all important factors influencing tyre-to-road grip.

The driver should take into account all such factors whilst driving, and even when the vehicle has beenfitted with new tyres, the driver should always be aware of these factors and not be dependent only onthe tyre itself.


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3.3.1.2 Tyre wear

For any given tyre, under given conditions, road holding is gradually decreased with increased tyre wear.The driver should always be aware of this. At any time during the life of a tyre a driver might be facedwith dangers of skidding that did not exist a moment before.

3.3.1.3 Tread depth

It is recommended that no vehicle be operated with tyres that do not have a minimum tread pattern depthof 1,0 mm in all the main grooves across the full width of their tread contact area and around the full tyrecircumference, with the exclusion of areas where tread-wear indicators or tiebars (or both) exist.

Drivers would be unwise to believe that they would be entirely safe driving at high speed on a wet roadprovided their tyres have at least 1 mm or more of remaining tread.

Safety is a matter of individual responsibility and of adapting one's driving behaviour and style to roadand tyre conditions.

3.3.1.4 Speed rating symbols

The speed limits and the interdependent load capacities for different categories of tyres are identified bythe applicable speed rating symbols.

Tyres used for passenger cars, motorcycles and light trucks are usually marked with a speed ratingsymbol, and consideration is being given to including such marking on certain commercial tyres in thefuture.

3.3.1.5 Load and speed rating guarantee

Tyre manufacturers guarantee the load and speed rating of the tyres produced at their productionfacilities only for the original tread life of the tyres. After the retreading of a tyre, the person who carriesout the retreading process is responsible for determining the load and speed capability of the tyre.

3.3.2 Passenger car tyres

3.3.2.1 Tread-wear indicators

In the case of a tyre of nominal diameter exceeding 305 mm, the tyre includes at least six transverserows of tread-wear indicators, approximately equally spaced and situated in the principal grooves of thetread. The tread-wear indicators are such that they cannot be confused with the rubber ridges betweenthe ribs or blocks of the tread.

In the case of a tyre of dimensions suitable for mounting on a rim of nominal diameter 305 mm (code 12)or less, four rows of tread-wear indicators are acceptable.

The tread-wear indicators provide a means of indicating when the tread grooves are at least 1,00 mmdeep or more.

The height of tread-wear indicators is determined by measuring the difference between the depth, fromthe tread's surface, at the top of the tread-wear indicator, to the bottom of the tread groove close to theslope at the base of the tread-wear indicator (see figure 4).


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3.3.2.2 Tyre mounting or storage

The maximum permissible inflation pressure during tyre mounting, or in the case of vehicles in storageor transit, is 280 kPa.

This does not apply to tyres for temporary-use spare wheels, in which case the tyre manufacturer shallbe consulted.

3.3.2.3 Temporary-use spare wheels

The current trend for fuel-efficient vehicles has resulted in smaller, lighter passenger cars, which, in orderto conserve available space, sometimes necessitates the fitment of a temporary-use spare wheel in lieuof the heavier, larger regular wheel.

A temporary-use spare wheel is intended for temporary road use under restricted conditions, and maybe fitted by the vehicle manufacturer.

The manufacturer's design speed of the temporary-use spare wheel should be at least 120 km/h, but themaximum operational speed shall be restricted to 80 km/h.

On the outer face of the tyre, in a suitable location, a fixed inscription should display, in contrastingcharacters, in one of the official languages, at least the following information:

TEMPORARY USE ONLY! MAX. 80 km/h!

If use of the temporary-use spare wheel is restricted to a specific axle, the following information shouldbe included in one of the official languages:

FOR USE ONLY ON A FRONT (REAR) AXLE

For vehicles that have at least four wheels, the load capacity of the temporary-use spare wheel shouldbe at least equal to one-half of the highest of the maximum axle loads of the vehicle; if its use isrestricted to a specific axle, its load capacity should be at least equal to one-half of the maximum loadof that axle.

The owner's manual of the vehicle should include at least the following information:

- a statement of the risk resulting from non-compliance with the restrictions on the use of a temporary-use spare wheel, including, as appropriate, a statement relating to use if restricted to a specific axle;

- an instruction to drive with caution when the temporary-use spare wheel is fitted, and to reinstall aregular wheel as soon as possible;

- a statement that operation of the vehicle is not permitted with more than one temporary-use sparewheel fitted at the same time; and

- a clear indication of the inflation pressure specified by the vehicle manufacturer for the tyre of thetemporary-use spare wheel.

In the case of a vehicle equipped with a deflated temporary-use spare wheel, a description of theprocedure for inflating the tyre and an inflating device should be provided with the vehicle, permitting thetyre to be inflated to the pressure specified for temporary use within a maximum of 5 min.


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3.3.3 Commercial vehicle tyres

3.3.3.1 Commercial vehicle tyres driven unloaded

Highway type (rib and lug design) commercial tyres need special protection when the vehicle is drivenunloaded over long distances. Typical of these conditions is the road delivery of new vehicles fromassembly plants or body builders. Overinflation of the tyres owing to reduced loading should be avoided.

Just as underinflation can promote damage leading to tyre failure, so can overinflation. Overinflationunder driveaway conditions causes excessive heat to build up in the centre of the tyre tread, which cansubsequently cause premature tyre failure.

Commercial tyres on driveaway vehicles should be inflated to a pressure sufficient to carry the imposedtyre load; however, this should not be less than that shown in the relevant tables (see SABS 1550-3).

City bus tyres and special construction tyres may require additional speed restrictions and cooling stops,but in such cases the tyre manufacturer should be consulted.

3.3.3.2 Speed limitations - city bus tyres

Tyres marked ‘CITY BUS' are for use on buses limited to slow-speed stop-start intra-city service. Themaximum speed should not exceed 60 km/h.

3.3.4 Agricultural vehicle tyres (see SABS 1550-6)

3.3.4.1 Transportation inflation pressures

Tyre types SA-AT-1B and SA-A1-1A: The transportation inflation pressure should not exceed themaximum pressures for the ply ratings shown.

Tyre types SA-WT-2C and SA-LS-WT: The transportation inflation pressure may be increased to210 kPa. (Consult tyre manufacturers for minimum tyre transportation pressure.) This higher inflationpressure should be reduced to operating pressure BEFORE the tractor is removed from the carrier.

3.3.4.2 Cyclic loading service

In the case of agricultural tyres on drive wheels used in cyclic loading service (excluding hillsidecombines) without sustained high torque at speeds up to 8 km/h, loads shown for SA-WT-2C tyres maybe increased by 50 % with a 30 kPa increase in inflation pressure.

3.3.5 Industrial tyres - rim loads and inflations

Rim dimensions are standardized for size and contour only, and particular tyre and rim combinations aredesignated to ensure proper mounting and fit of the tyre to the rim. The load and cold inflation pressureimposed on the rim and wheel should not exceed the rim and wheel manufacturers' recommendations,even though the tyre may be approved for a higher load or inflation. Rims and wheels may be identified(stamped) with a maximum load and maximum cold inflation rating. For rims and wheels not so identifiedor for service conditions exceeding the rated capacities, consult rim and wheel manufacturers todetermine rim and wheel capacities for the intended service.


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3.3.6 Off-the-road vehicle tyres driven unloaded

Off-the-road tyres need special protection when a vehicle is driven over the highway for delivery ormoved to a new job site.

Vehicles shall be empty during transit and overinflation of tyres due to the reduced load shall be avoided.Just as underinflation can cause damage leading to tyre failure, so can overinflation. Refer to the relevanttables for the correct inflation pressure for the loads being carried (see SABS 1550-5).

In addition to the above, further precautions should be taken to protect extra heavy construction off-the-road tyres on driveaway vehicles. If the precautions are not observed, excessive tyre heat will build upand may cause subsequent premature failure. These precautions are given in tables 1 and 2 and applyto off-the-road tyres on all vehicles in transit, driven or towed.

For off-the-road vehicles fitted with highway truck type commercial tyres, refer to 3.3.3.1.

Table 1 - Driveaway precautions

1 2 3 4 5

Driveawaycondition

Driveaway category

(1) (2) (3) (4)

Max. highway speedMax. travel time in any one 24 h periodMin. cooling stopMax. distance between cooling stopsOR (whichever occurs first) Max. travel time between cooling stopsMin. cooling stop after 4 h of operationFor loads and inflations refer to tables for tyres:

50 km/h12 h

30 min80 km

OR2 h1 h

SA-EXP-1

30 km/h12 h

30 min30 km

OR1 h1 h

SA-EXP-1SA-EXP-2

30 km/h8 h

30 min20 km

OR1 h1 h

SA-EXP-1

Driveawaynot

recommended.Consult tyre

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Table 2 - Driveaway categories for specific tyre types

1 2 3 4

Tyre type Industrycode*

Driveawaycategory Remarks

Narrow base (non-ballasted) G-2G-3

ML-2ML-3E-3E-4L-4L-5

(1)(1)(1)(1)(1)(2)(4)(4)

NOTE - For category (1)tyres at 30 km/h operation,table 8 loads may beincreased by 6,5 %.(Refer to table 8 inSABS 1550-5)

Wide base (non-ballasted) G-3E-3L-3L-4L-5

L-5SL-5/L-5S

(2)(2)(4)(4)(4)(4)(4)

Narrow or wide base(with water ballast)

G-2G-3

ML-2ML-3E-3E-4L-3L-4L-5

L-5SL-5/L-5S

(3)(3)(3)(3)(3)(3)(4)(4)(4)(4)(4)

Narrow or wide base(with dry ballast)

All (4)

*Consult tyre manufacturer for industry codes not listed. For listed industry codes, refer to relevant tyre tables (seeSABS 1550-5).

3.3.7 Warning on the use of aircraft and motor racing type tyres

Certain tyres, manufactured for specific purposes, are NOT TO BE USED on motor vehicles for operationon public roads.

3.3.7.1 Aircraft tyres

3.3.7.1.1 On most aircraft tyres, the size marking is distinctive and indicates the overall diameter andoverall width in inches, e.g. 49 x 17. Exceptions exist in the smaller sizes fitted to light aircraft where thesize indicates section width and rim size, e.g. 6,00-6.

3.3.7.1.2 The moulded sidewall stencil invariably indicates the month and year of original manufacture,e.g. JUN 71.

3.3.7.1.3 Tread patterns are of a simple grooved type, consisting of four or more plain ribs without sipes.

3.3.7.1.4 Sidewalls are generally plain without undue embellishment and are usually marked withcoloured paint where the carcass has been vented.


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3.3.7.2 Motor racing tyres

3.3.7.2.1 Most racing tyres are marked 'RACING'. Tread compounds and constructions are indicatedby moulded stencils, as are the usual date code and serial number.

3.3.7.2.2 Present-day racing tyres are extremely wide, the relation between the width and the height ofthe tyre being of the order of 3:1.

3.3.7.2.3 The method of size marking is distinctive since it is usually a triple marking, e.g. 155/550-13,which refers to tread width, overall diameter and rim diameter.

3.3.7.2.4 No side rubbers are fitted and therefore casing cords are usually visible.

3.3.7.2.5 Most modern tyres have a slick type of tread, i.e. the tread is smooth except for small shortgrooves, slits or holes, which act as tread-wear indicators.

3.3.7.2.6 Tyres with definite recognizable patterns would be in conventional sizes and probably ratherold. However, tyres for wet conditions have a special bold pattern and special safety tread compounds.

3.3.7.2.7 Racing tyres are not made in South Africa, and therefore do not bear "Made in South Africa"on the sidewalls.

3.4 Fitment and replacement of tyres, tubes and valves

3.4.1 General

The choice of a vehicle tyre is closely connected with the mechanical, load and speed characteristics ofa vehicle. On passenger cars, it is recommended that tyres that are designed for the maximum speedthat can be attained by a vehicle be fitted, irrespective of any speed limits that may be in force at the timeof manufacture.

3.4.1.1 Tyre, rim and inner tube combinations, as applicable, should always be maintained in a state ofstatic and dynamic balance. During normal vehicle operation, tyres may suffer from creep (relativemovement between tyre and rim), and hence the wheel assemblies require periodic checking andrebalancing.

3.4.1.2 Inner tubes should always be identified or marked with the applicable tyre sizes to which theymay be fitted.

3.4.1.3 Attention should be paid to fitting valves correctly and squarely in the rim valve holes to avoiddamage to the inner tube or flap. On the inner tyres of twin wheel assemblies, it is advisable to use valveextension pieces for those valves that are in inaccessible locations. Owing to tyre creep, inner tubes andvalves may also be affected after continued vehicle operation, and any tyre rim assemblies showingsigns of valve misalignment should be deflated and have the condition rectified.

3.4.1.4 Replacement tyres should always be of the type fitted as original equipment by the vehiclemanufacturer, or as recommended in the vehicle manufacturer's handbook or as permitted by the tyremanufacturer.

3.4.1.5 It is advisable, when replacing tyres, to fit a new inner tube and flap in a tyre requiring a tube,or a new valve in the case of a tubeless tyre requiring a valve only.


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3.4.1.6 Replacement tyres should be suited to the actual loads on the relevant axles and in no caseshould the load ratings, whether for single fitment or dual fitment, be lower than the evenly distributedmass per axle of the vehicle as approved by the vehicle manufacturer or as may be limited by road trafficregulations.

3.4.2 Mixed fitments of tyres on passenger vehicles

Diagonal-ply tyres and radial-ply tyres should not be mixed, the only exception to this rule being whena temporary-use spare wheel has to be used (see 3.3.2.3 and 3.4.5).

In general, all makes of diagonal-ply tyres of a given size, type and rating are interchangeable.

In the case of textile and steel radial-ply tyres, if mixing occurs, the preferential fitment should be withthe textile radial-ply tyres on the front axles and with the steel radial-ply tyres on the rear axles.

3.4.3 Mixed fitments of tyres on commercial vehicles

On commercial vehicles, there would be no objection to mixed fitments of radial-ply tyres on the front anddiagonal-ply tyres on the rear, or vice versa, provided certain basic recommendations are observed.

3.4.3.1 On twin steer axled vehicles, both axles should be fitted with the same tyre construction, namelydiagonal ply or radial ply.

3.4.3.2 Rear axle fitments, whether drive or trailing axles which may be of single, tandem or triaxleconfiguration, should be fitted with tyres of the same construction, namely diagonal ply or radial ply.

3.4.4 Dual fitment of tyres

In the case of commercial vehicles, it is recommended that tyres be twinned only when they are of thesame type and of the same nominal size, and have comparable diameters. If a diagonal ply is twinnedwith a radial ply, even of comparable diameter, this can lead to irregular wear, and casing fatigue will beaggravated owing to the uneven loading on the tyres resulting from the different flexing characteristics.

Temporary mixing of the two types in an emergency is permissible, but in such cases the radial-ply tyreshould always be fitted to the inner wheel.

Because of the foregoing, replacements should always be effected in pairs of the same type.

3.4.5 Temporary fitment of a spare wheel

The recommendations of 3.4.2, 3.4.3 and 3.4.4 may be temporarily waived when a spare wheel has tobe used to reach a destination, but the driving technique (speed and braking, etc.) will requiremodification according to the existing road conditions.

3.5 Tyre and rim damage and maintenance

3.5.1 General

3.5.1.1 Consult a qualified tyre technician regarding any visible surface damage or tyres showingevidence of rupture, bulging or tread separation.


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3.5.1.2 A tyre showing a deep hole or cut reaching to or exposing the casing plies (or belts) on any partof its outside surface, or showing evidence of rupture or separation, should be removed from service.This does not mean that the tyre has to be rejected. After qualified examination, internally and externally,the tyre may be deemed repairable for further service.

3.5.1.3 Any tyre that is known to have suffered a violent impact against any obstacle should besubjected to qualified examination. Interior damage may be present that could lead to sudden tyre failurelater on.

3.5.1.4 A tyre mounted on its rim allows only visual inspection of the outside sidewalls and tread. Moderntyre manufacture and design are of such complexity that a mere outside inspection, without demountingthe tyre, cannot give a true picture of its suitability for continued service, unless of course in the case ofvery obvious defects such as in 3.5.1.2.

Tubeless plug repairs should NEVER be considered permanent. The tyre should be removed from therim and examined for possible internal damage. If no internal damage exists, a proper vulcanized repairshould be effected and this should include a suitable patch on the inner liner.

3.5.1.5 Tread-wear appearance should be examined periodically, particularly on the front axle. Abnormalor uneven wear may be an indication of a mechanical defect of the vehicle (incorrect wheel alignment,steering mechanism play, high spots on the brakes, etc.). It is therefore essential that such mechanicalparts of the vehicle be kept in good order and readjusted as found necessary.

3.5.1.6 If the vehicle is capable of high speed, all tyre and wheel assemblies should be kept andmaintained in the best state of static and dynamic balance. Tyre and wheel imbalance, besides causingabnormal tyre wear, can also result in serious steering defects and problems.

3.5.1.7 The condition of all wheels should be checked periodically. Rim flanges and wheel dishes shouldnot be cracked, damaged or distorted. Wheel nuts should be kept tightened to the vehicle manufacturer'srecommended torque and adjusted in cross-sequence to avoid lateral run-out of the wheel. Cracked rimsor wheels should be scrapped. Deflate such tyre/rim combinations before removing them from thevehicle. No repair welding should ever be carried out on cracked rims or discs.

3.5.2 Tyre reconditioning and grooving

3.5.2.1 Tyre reconditioning

Reconditioning of tyres should be carried out in accordance with the relevant requirements of thefollowing parts of SABS 1000:

SABS 1000-1, The production of reconditioned tyres - Part 1: Definitions.

SABS 1000-3, The production of reconditioned tyres - Part 3: Repairs.

SABS 1000-4, The production of reconditioned tyres - Part 4: Passenger car tyres.

SABS 1000-5, The production of reconditioned tyres - Part 5: Light truck cross-ply tyres.

SABS 1000-6, The production of reconditioned tyres - Part 6: Bus and truck cross-ply tyres.

SABS 1000-7, The production of reconditioned tyres - Part 7: Tyres reconditioned by the pre-cured treadprocess.

NOTE - SABS 1000 is currently being revised, and a new part is being considered concerning the reconditioning of radialsteel truck tyres.


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3.5.2.2 Tyre grooving

Passenge r ca r tyres manufactured in South Africa a r e NOT designed for regrooving.

Commercial vehicle tyres CAN b e designed for regrooving and this MAY b e done for certain operating conditions, but t h e tyre manufacturer should b e consulted. Regrooving is only allow- e d on tyres that a r e marked "REGROOVABLE" o r with the symbol "T.J'' o r with the symbol . Regulation 347(i) of t he Road Traffic Act, 1 9 8 9 (Act 2 9 of 1989) , prohibits t he operation of a vehicle with a regrooved tyre that h a s a bead diameter of 430 mm o r less.

3.5.3 Damage and maintenance with particular reference to commercial vehicle tyres and rims

In respect of commercial vehicle tyre and rim combinations, personal safety is paramount when maintenance services a r e being conducted. No tyre should ever b e removed from its wheel before having been deflated in the correct manner.

It is absolutely imperative that safety precautions b e carefully studied and correct training b e given to all personnel dealing with fitment of tyres to multipiece rims.

An employer should establish a s a f e operating procedure for servicing multipiece rim wheels and should ensu re that employees a r e instructed in and follow this procedure:

3.5.3.1 A tyre should b e completely deflated by removal of the valve core before it is demounted.

3.5.3.2 A tyre should b e completely deflated by removal of the valve core, before a wheel is removed from the axle in either of the following situations:

a ) when the tyre h a s been driven underinflated a t 8 0 % of its recommended pressure or less; or

b) when there is obvious or suspected d a m a g e to the tyre or to wheel components.

3.5.3.3 Approved tyre fitting lubricant should b e applied to bead and rim mating surfaces during assembly of t he wheel and inflation of t he tyre.

3.5.3.4 A tyre should only b e inflated when contained by a restraining device or safety cage , except that, when the assembly is on a vehicle, a tyre that is underinflated but h a s more than 8 0 % of the recommended pressure, may b e inflated while the wheel is on the vehicle.

3.5.3.5 When a tyre is being partially inflated without a restraining device or safety cage , for t he purpose of seating the lock ring o r to round out t he tube, such inflation should not exceed 150 kPa.

3.5.3.6 Whenever a tyre is in a restraining device, t he employee should not rest o r lean a n y part of his body o r equipment on or against t he restraining device.

3.5.3.7 After tyre inflation, the tyre, rim and rings should b e inspected while still within the restraining device to make su re that they a re properly sea t ed and locked. If further adjustment to the tyre, rim o r lock ring and s ide flange is necessary, t he tyre should b e deflated by removal of the valve core before the adjustment is made.

3.5.3.8 No attempt should b e m a d e to correct t he seating of s ide f langes and lock rings by hammering, striking o r forcing the components while t h e tyre is pressurized.

3.5.3.9 Cracked, broken, bent o r otherwise damaged rim components should not b e reworked, welded, brazed o r otherwise heated.


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3.5.3.10 Make a final check of the gap of ring-to-rim assembly and the proper position of both tyre beadsbefore removing the tyre from the restraining device. If the gap exceeds 9,5 mm, STOP.

Replace with a new side ring.

3.5.3.11 Always remove rust or other foreign material before assembly. Excessively corroded partsshould be replaced.

3.6 Mismatched rim and wheel parts of particular importance on commercialvehicles

3.6.1 Rims

3.6.1.1 On commercial vehicles, mismatched rim parts are extremely dangerous and could result insevere injury to personnel.

3.6.1.2 Most highway rims look alike, but all vary somewhat in certain design features. It is thisdifference between rims of different types that makes part mixing a hazardous business. A close, properfit between rim parts is essential to long life as well as to the operating safety.

3.6.1.3 The fitment of incorrect rim components is rife, and transport operators and their maintenancestaff appear to be unaware of the danger in which they are placing their drivers and other road users.

Fitting incorrect components may cause the following types of tyre failure: excessive flexing; overheating;sidewall failure; tyre slippage; tube pinching; valve stem tear-outs; ply separation; blowouts; beadchafing; bead distortion and incorrect bead seating resulting in wheel assembly balance and runoutproblems.

3.6.1.4 Side rings, flanges and lock rings of different types very often appear to be properly seated, butactually wide gaps are present, which are frequently difficult to see. The gap on the lock ring or springflange should be between 2,0 mm and 9,5 mm when the tyre is inflated and should not exceed 12,7 mmwhen the tyre is deflated.

3.6.1.5 It is imperative that all replaceable components such as lock rings, loose flanges and springflanges only be replaced with identical new parts from the original manufacturing source or reputablesuppliers.

3.6.2 Wheels

The majority of commercial wheels currently fitted to South African built commercial vehicles have aspherical (radius) hole seating of European design, which mates with the matching radius of the wheelstud loose collar and plain wheel nut both to centralize and to support the wheel on the vehicle.

3.6.2.1 Some British vehicles have a similar type of wheel mounting, but this depends on a conicalseating (40° taper), which is different from the European spherical seating. Consequently, theseEuropean and British wheel nuts should not in any circumstances be interchanged, even though itappears to be possible. The spherical and conical seating do not mate together, and loose wheels andbroken studs, with their attendant dangers, are the likely result.

3.6.2.2 Other commercial vehicles have spigot-mounted wheels where the wheel is centralized andsupported by the machined fit of the wheel centre bore on the hub spigot. In this type of mounting, thewheel has plain stud holes and flat-faced nuts (usually with captive washers) which simply hold the wheelon the vehicle and have no part in its centring.


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3.6.2.3 It is most important that, during mounting on the vehicle, all wheels be centred correctly to avoidover-strained or fractured studs, distortion of wheel hub flanges and brake drums, loose wheels andelongated stud holes.

3.6.2.4 The vehicle should be jacked up so that the tyre is clear of the ground. Push the wheel or twinwheels home on the studs, and screw all nuts lightly. No one nut should be screwed fully home whileothers are still loose. The final tightening should be undertaken gradually and progressively by givingshort turns at a time to each nut in the sequence shown in figure 3.

3.6.2.5 Once the wheel is located correctly, the final torque as specified by the vehicle manufacturershould be applied in the sequence given in figure 3.


Rim ' Bead Section width S

c *

Overall width

TYRE DIMENSIONS IN THE TABLES

The t y r e dimensions in the tables apply t o a new in f la ted and unloaded t y r e

Figure 1 - New tyre dimensions


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Figure 2 - Motor cycle and motor scooter tyres - tread and configurations


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A six stud mounting An eight stud mounting

A ten stud mounting

Org. 11795/E

Figure 3 - Commercial vehicles - wheel nut tightening sequence


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Section A - A

Figure 4 - Tread-wear indicator

Section B - B

Figure 5 - Tiebar Dr 9.12440/E


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Documents

edition of tyre

approved subscription

freemailing clients

etrto european tyre

rim association

tredco data book

rim technical organisationsmmt

dunlop tyres pty