ISO 4927:2005

Overview

ISO 4927:2005 - Road vehicles - Elastomeric boots for cylinders for drum type hydraulic brake wheel cylinders using a non-petroleum base hydraulic brake fluid (service temperature 120 °C max.) - specifies performance tests for moulded rubber (elastomeric) boots used as end closures on drum‑type wheel brake cylinders. The standard ensures boots prevent ingress of dirt and moisture that can cause corrosion or impair brake operation. It applies to both plain and reinforcement‑insert boot types intended for use with brake fluids conforming to ISO 4925. The rubber shall be suitable for operation from −40 °C to +120 °C.

Key topics and technical requirements

• Scope & exclusions: Covers workmanship, marking, packaging and performance tests. Does not specify chemical composition, tensile strength, elongation at break, or adhesion strength of rubber-to‑reinforcement.
• Workmanship and marking: Boots must be free of defects (blisters, pin‑holes, cracks) and bear manufacturer identification; may be marked “ISO 4927”.
• Performance tests included:
  • Resistance to fluid at elevated temperature (using ISO 4926 reference fluid): volume change within −15% to +15%; hardness change within −10 to +10 IRHD; inspect for disintegration.
  • High‑temperature stroking: 70 h cycling at 120 °C; no through‑wall flexure cracks; must fit tightly.
  • Low‑temperature stroking: operation at −40 °C to −43 °C; boots must not crack or loosen.
  • Tension set: aged at 120 °C for 70 h; max average tension set ≤ 75%.
  • Heat resistance (static): 70 h at 120 °C; no cracking, hardness change −5 to +10 IRHD, no tackiness.
  • Ozone resistance (per ISO 1431): exposure (~50 × 10‑8 by volume ozone at 40 °C) for 70 h; no surface cracking under 2× magnification.
• Test methods & references: Normative references include ISO 48 (hardness), ISO 188 (aging), ISO 1431‑1 (ozone), ISO 4925/4926 (brake fluids), and ISO 4928 (stroking fixtures).

Applications and who uses it

ISO 4927:2005 is used by:

• Brake component manufacturers and molders for design verification and production qualification.
• OEMs and suppliers specifying acceptance criteria for wheel cylinder boots.
• Quality engineers and test laboratories performing durability and compatibility testing.
• Procurement/specification writers who require standardized performance evidence for elastomeric boots used with non‑petroleum base hydraulic brake fluids.

Practical uses include material selection validation, production lot testing, supplier audits, and ensuring long‑term serviceability of drum‑type hydraulic brake systems.

Related standards

• ISO 4925 / ISO 4926 - non‑petroleum brake fluids and reference fluids
• ISO 4928 - related stroking fixtures and test apparatus
• ISO 6117, ISO 7633 - related elastomeric boot standards for other fluids or service temperatures

Keywords: ISO 4927, elastomeric boots, drum type hydraulic brake wheel cylinders, non‑petroleum brake fluid, performance tests, ozone resistance, high/low temperature stroking.