Overview
ISO 7629:1987 - Road vehicles - Brake linings - Disc brake pads - Evaluation of surface and material flaws after testing - defines a standardized, visual and dimensional method for identifying and reporting post-test surface and material defects on disc brake pads. The standard describes four flaw types (cracks, edge flaking, blistering/pitting, and material or lamina separation), prescribes simple measurement procedures using a transparent millimetric grid, and specifies how to express results for quality assessment and comparison.
Key topics and requirements
- Scope: Applies to disc brake pads for road vehicles; focuses on post-test evaluation of surface and material flaws.
- Flaw classification: Four types are defined:
- Type I - Cracks (measure individual crack lengths; count cracks in the densest 10 mm × 10 mm area).
- Type II - Edge flaking (area measurement; may be approximated as a × b).
- Type III - Blistering and pitting (measure and sum flaw areas).
- Type IV - Material or lamina separation (measure separation length L and sum of lengths).
- Preliminary measurements:
- Measure and record lining height H (median line or maximum for asymmetric shapes).
- Measure and record friction surface area A0.
- Establish a reference point A at the middle of height H for grid placement.
- Measurement method:
- Use a transparent millimetric grid to locate and size defects.
- Place grid on point A (for cracks) or on the working surface (for area defects).
- Only include flaws detectable with the naked eye.
- Expression of results:
- Cracks: report longest crack and sum of all crack lengths (also number per 100 mm).
- Edge flaking/blistering/pitting: report total area as a percentage of surface area A0; record biggest flaw area and the sum of all flaw areas.
- Separations: report longest separation and sum of separation lengths as percentage of lining height H.
Practical applications
- Quality control and acceptance testing of disc brake pads after laboratory or vehicle tests.
- Comparative evaluation in product development and brake component R&D.
- Failure analysis and forensic assessment following in-service incidents.
- Input to conformity assessment, supplier audits, and production inspection procedures.
Who uses this standard
- Automotive OEMs and Tier 1 brake suppliers
- Materials and brake testing laboratories
- Quality engineers and product validation teams
- Regulatory and certification bodies concerned with braking component durability
Related standards
- Prepared by ISO/TC 22 (Road vehicles). ISO 7629 is complementary to performance and endurance test standards for braking systems and material test methods; users should consult current ISO braking and material testing standards for test procedures and acceptance criteria.
Keywords: ISO 7629:1987, disc brake pads, brake linings, surface defects, cracks, edge flaking, blistering, pitting, material separation, millimetric grid, brake pad testing.
Open preview (PDF)Road vehicles — Brake linings — Disc brake pads — Evaluation of surface and material flaws after testing
