Overview
ISO 11157:2005 - "Road vehicles - Brake lining assemblies - Inertia dynamometer test method" - defines a laboratory dynamometer procedure to homologate alternative brake lining types (including pads) mounted on original equipment. The standard is used to demonstrate equivalence to the linings fitted at the vehicle’s original approval, in accordance with UN‑ECE Regulation No. 13‑09 (Annex 15). It applies to road vehicle categories M, N and O (passenger cars, goods vehicles and trailers) and is intended for vehicle, axle or brake manufacturers and their accredited representatives.
Key topics and technical requirements
- Scope of testing: Comparison-based homologation of alternative brake linings using an inertia dynamometer to represent the part of vehicle inertia braked by the wheel(s) under test.
- Test types: Defined procedures include:
- Type‑0 (cold performance) - cold MFDD (mean fully developed deceleration) vs. input; establishes the Type‑0 reference value.
- Type‑I (fade test) - heating procedure with repeated braking to evaluate fade behaviour.
- Type‑II (downhill behaviour) - assesses downhill braking performance.
- Type‑III (additional fade) - further fade characterization as required.
- Instrumentation & equipment: Continuous recording of rotational speed, stopping time, temperature at lining or disc mid‑thickness, control line pressure/force, and brake output torque. The same dynamometer must be used for all tests.
- Test conditions:
- Brake linings shall be at least 80% bedded before testing.
- Initial lining temperature ranges specified (typically 50 °C to 100 °C for initial snubs).
- Dynamometer rotational inertia and test speeds are set to represent vehicle conditions (tolerances apply).
- Cooling air, if used, must follow the standard’s prescribed velocity relation to vehicle test speed.
- Performance limits & evaluation:
- Comparison limits: e.g., Type‑0 MFDD for the alternative lining shall be within ±15% of the original equipment MFDD for the same input.
- Data assessment procedures, stopping-distance measurement accuracy and MFDD calculation rules are specified.
Applications and users
- Vehicle manufacturers seeking approval for alternative brake linings on an already-approved vehicle type.
- Axle and brake manufacturers (especially for category O trailers) applying for component approval.
- Technical services and homologation authorities performing conformity and comparative testing.
- Brake component suppliers and independent testing laboratories conducting QA, R&D, or aftermarket lining validation to UN‑ECE requirements.
Related standards
- Normative references cited in ISO 11157: ISO 611, ISO 1176, ISO 3833, and UN‑ECE Regulation No. 13 (09 series) - these define related terminology, vehicle categories and braking approval framework.
Keywords: ISO 11157, inertia dynamometer, brake lining assemblies, MFDD, brake pad homologation, UN‑ECE Regulation No.13, brake fade test, vehicle brake testing.