BS AU 50-1.3.2:1989 download.British Standard Automobile Series Tyres and wheels Part 1. Tyres Section 3. Off-the-road tyres Subsection 3.2 Specification for narrow and wide base tyre loads and inflation pressures [ISO title: Narrow and wide base off-road tyres and rims — Part 2 : Loads and inflation pressures].
0 Introduction
ISO 4250 provides technical details on the designation and dimensions of off-road tyres and rims, as well as load ratings for these types of tyres.
BS AU 50-1.3.2 consists of three parts:
Part 1 Tyre designations and dimensions.
Part 2: Loads and inflation pressures.
Part3 Rims.
1 Scope
This part of ISO 4250 gIves working definitions of masses and load cycles, and sets out tyre loads and reference inflation pressures for narrow and wide base off-road tyres.
2 Field of application
This part of ISO 4250 applies to tyres primarily Intended for off- road machines.
3 Definitions
3.1 DefInitions of masses
3.1.1 maxImum load: Maximum loads of individual tyres determined by manufacturer’s rated gross machine mass (GMM) distribution assigned to each axle, divided by the number of tyres for that axle.
NOTE — The maximum GMM includes masses calculated In 3.1.1.1 to 3.1.1.6 inclusive.
3.1.1.1 operatIng mass (net weight): Actual mass of the base machine with equipment specified by the manufacturer, operator (75 kg), full fuel tank, and full lubricating, hydraulic and cooling systems.
3.1.1.2 optIonal equipment mass: Difference In operating mass between the optional item and standard item replaced (such as engine, brakes, tyres, etc.). This Includes the operating mass of additional items offered by the manufacturer which are not replacements for standard items (such as cabs, body-liners, side-boards, air conditioners, etc.).
3.1.1.3 mass of special modifications: Difference In the operating mass of the machine due to modifications not previously covered In optional equipment mass (such as additional reinforcements, etc.).
3.1.1.4 payload: Total mass of the material being carried.
3.11.5 tyre ballast: (If used, shall also be included in determination of GMM.)
3.1.1.6 field modifications: Operating mass change due to machine alterations made other than by the original manufacturer (such as modifications for additional capacity, reinforcements, etc.).
3.2 Definitions of operating conditions
3.2.1 maximum speed: Peak velocity attained by the machine.
3.2.2 earth-movIng haulage cycle: Cyde where machine self-loads or receives a load from loading equipment, transports it elsewhere and returns unloaded. Transportation usually occurs over unimproved surfaces at medium speeds, up to 65 km/h, and short distances, up to 4 km away.
NOTE — Machines in this category are mainly haulage trucks (dumpers) and tractor-scrapers.
3.2.3 loader cycle: Cycle where the machine is used to pick up material and move it a short distance away. Tyre loads fluctuate depending on the conditions Involved when the equipment picks up the load. Transportation speeds are low, up to 10 km/h, and distances are short, usually less than 75 m away.
3.2.4 load carry cycle: Cyde where the machine, primarily Intended for loader service, picks up a load, transports it elsewhere and returns unloaded. Transportation usually occurs over unimproved surfaces at low speeds, up to 25 km/h, and rather short distances, up to 600 m.
NOTE — Machines In this category consist mainly of loaders, log stackers and material handling equipment. Tyre manufacturers should be consulted for specific conditions.
3.2.5 dozer (tractor) cycle: Condition whore a machine Is used to move materials (usually earth) by pushing, dragging or grading. Tyre loads are relatively constant and speeds are low, up to 10 km/h. Travel distances vary depending on work situations.
3.2.6 grader cycle: Condition where a machine is used in construction and road maintenance. Tyre loads are relatively constant during the work cycles. Grader speeds are slower during working periods with typical transportation speeds reaching about 40 km/h. Travel distances vary depending on work situations.
3.2.7 creep: Movement of equipment at a very low speed (commonly not over 120 m In 60 mm). During creep motion, loads on the tyres are usually very lgh and consideration must be given to the type of surface over which the equipment Is travelling. Tyre manufacturers should be consulted for specific conditions.
3.2.8 drIve-away: Movement of a machine from one location to another under non-working conditions. This movement occurs during transportation of a machine from site to site. Tyre manufacturers should be consulted for specific conditions.
NOTE — Load/speed/distance tables In this part of ISO 4250 are not applicable to drive-away conditions.
4 SpecIal conditions
For longer hauls and/or speeds In excess of those indicated in the tables, the lyre manufacturers should be consulted for instructions regarding permissible loads and the required inflation pressures.
5 Selection for new machine design
Selection of size and strength Index of the lyre used on each axle shall be based on the highest individual wheel load (determined by GMM distribution, including load transfer) and the machine application.
Maximum load per tyre shall not be greater than specified In the applicable tables.
The performance of machines fitted with off-road tyres depends on the operating conditions, and more particularly on the specific ground pressure which is governed by the Inflation pressure. It is therefore advisable to select tyre size on the basis of low Inflation pressure.
6 Inflation pressures — General
6.1 RIm and wheel manufacturers should be consulted to determine if the rim and wheel are of sufficient strength for the intended service conditions (Inflation pressure and load).
6.2 Inflation pressures shown in the load inflation tables are reference pressures and do not include any pressure build-up due to vehicle operation.
6.3 In agreement with tyre manufacturers, Inflation pressures may be varied to compensate for extremes of atmospheric temperatures or special operating conditions.
6.4 For all tables the Inflation pressures are given for guidance only; in actual practice they may vary according to the operating conditions, In agreement with the tyre manufacturers.
7 Load/inflation tables
Load/inflation relations for diagonal ply rating tyres are given in tables 1 to 4: those for symbol-marked radial tyres are given in tables 5 and 6.
8 Bibliography
ISO 3877-1, Tyres, valves and tubes — List of equivalent terms — Part 1: Tyres.