Overview
ISO 9987:1990 - Motorcycles: Measurement of variation of dipped beam inclination as a function of load specifies a laboratory method to measure how a motorcycle’s dipped (low‑) beam direction changes when the vehicle attitude varies because of different loading conditions. The standard applies to two‑wheeled motorcycles and gives repeatable procedures, loading scenarios and measurement methods (visual, photometric, laser/inclinometer, vehicle‑attitude measurement) so manufacturers and test laboratories can quantify headlamp aim variation under real‑world loads.
Key topics and requirements
- Scope and units: Variation of dipped beam inclination is expressed in milliradians (mrad) or percent inclination (1% = 10 mrad), with sign convention for upward/downward deflection.
- Reference conditions: Initial inclination is measured on a motorcycle that has travelled at least 1 000 km and under specified tyre pressures and “vehicle kerb mass” conditions.
- Loading conditions (Annex A):
- Condition No. 1 - Rider alone (mass 75 kg ± 1 kg on seat).
- Condition No. 2 - Manufacturer’s maximum total mass simulated by added masses to reproduce declared axle loads.
- Measurement accuracy and reproducibility: Ground and screen positioning must allow reproducibility to ±0.5 mrad. Typical test protocol calls for three measurements (or 10 if spread > 2 mrad) and standardized rocking of the vehicle to settle suspension before readings. Ambient temperature for testing: 10 °C to 30 °C.
- Headlamp classes and methods (Annex B): Defines three classes of headlamp installations and acceptable measurement methods: direct projection on screen (visual or photometric), headlamp orientation using laser and mirror, and vehicle attitude measurement using inclinometers or direct height references.
- Photometric method (Annex C): Provides a procedure for locating the conventional cut‑off photometrically (photoelectric cells, light ratios, stabilized lamp voltage).
Applications and who uses it
- Motorcycle manufacturers - validate headlamp performance and design headlamp mounting/levelling systems.
- Certification and homologation bodies - verify compliance with national/regional lighting requirements and safety standards.
- Test laboratories and R&D teams - perform repeatable measurements of beam shift under defined payloads for product development and quality control.
- Safety engineers and lighting system suppliers - assess need for automatic or manual headlamp levelling and to optimize optical alignment under varying loads.
Related standards
- ISO 3833:1977 - Road vehicles: Terms and definitions (vehicle types).
- ISO 6726:1988 - Mopeds and motorcycles: Masses vocabulary.
- ISO 7227:1987 - Road vehicles: Lighting and light signalling vocabulary.
Keywords: ISO 9987:1990, motorcycle dipped beam, headlamp inclination, measurement method, loading conditions, photometric method, headlamp levelling, vehicle attitude, test procedure.