Overview
ISO 7457:1997 specifies standardized methods for determining the turning dimensions of wheeled earth‑moving machinery. The standard defines how to measure and report the turning radius, turning diameter, machine clearance diameter, outer and inner tyre clearance diameters, and the non‑stop 180° turn width for steerable wheeled machines. It applies to all steerable wheeled earth‑moving machinery regardless of steering type, with special provisions for skid‑steer machines (calculated from drawings).
Key topics and technical requirements
- Definitions and geometry: Clear definitions of turning centre, turning diameter/radius, machine clearance diameter and tyre clearance diameters (see figures in the standard).
- Test area: A compacted or paved, visually flat surface (≤ 3% grade), good tyre adhesion and legible markings.
- Test equipment: Basic measuring tools such as a steel tape (readable to 1 cm), plumb line and, where required, pedal‑effort measurement apparatus.
- Preparation and loading state: Tyre sizes and pressures set to manufacturer recommendations; movable equipment in transport position; load states specified (e.g., tractor‑scrapers/dumpers at rated maximum gross mass; wheel loaders, tractors, excavators and graders at empty machine mass plus specified attachments and operator).
- Test procedure:
- Perform full‑lock turns (right and left) at the lowest practicable speed.
- Mark tyre and machine projection points using a plumb line and measure diameters at not less than three equally spaced points; compute averages.
- Repeat each test three times and record the mean turning dimensions.
- Optionally determine diameters by calculation from three measured circumference points.
- Skid‑steer exception: Turning centre and diameters determined by calculation from drawings; some tyre clearance definitions are not applicable.
- Braked test option: Optional tests with inside non‑steered wheel brake applied at 450 N (or wheel‑locking effort if less) - results reported “with brakes”.
- Reporting precision: Linear dimensions reported in metres, correct to two decimal places. Required test report items include manufacturer, model/serial, equipment, tyre sizes/pressures, track widths and all measured diameters.
Applications and users
ISO 7457:1997 is used by:
- Equipment manufacturers for design verification and specification sheets.
- Test labs and OEM validation teams for performance testing and compliance.
- Fleet purchasers and specifiers comparing turning performance of wheel loaders, graders, dumpers, tractors and skid‑steer machines.
- Site planners and transport/logistics teams assessing manoeuvring clearance and road/yard space requirements.
- Regulatory and certification bodies assessing machine dimensional performance.
Related standards
Keywords: ISO 7457:1997, turning radius, turning diameter, machine clearance diameter, tyre clearance diameter, earth‑moving machinery, wheeled machines, turning circle test.
