ISO 7629:1987

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.