ISO 7308:1987

Overview

ISO 7308:1987 specifies the requirements and testing methods for petroleum-based brake fluid designed for stored-energy hydraulic brake systems in road vehicles. This international standard, developed by ISO Technical Committee 22 on Road Vehicles, ensures that such brake fluids meet strict performance and material compatibility criteria, especially in systems using synthetic rubber cups and seals based on butadiene-acrylonitrile copolymer or equivalent. The fluid is suitable for both systems with and without pumps but is not recommended for arctic operating conditions.

Key Topics

ISO 7308:1987 addresses several essential aspects to guarantee safety, reliability, and compatibility:

• Fluid Characteristics: The brake fluid must be green, visually clear, and free from suspended matter or sediment.
• Performance Requirements:
  • High boiling point to resist vaporization during extreme braking.
  • Specific viscosity at both high (100°C) and low (-40°C) temperatures for consistent system response.
  • Low water content and controlled hygroscopicity to minimize corrosion and fluid degradation.
  • Controlled foaming tendency and stability.
• Compatibility and Safety:
  • Compatible with polymer-based rubber seals commonly used in hydraulic brake systems.
  • Maintains physical and chemical stability without causing rubber degradation or excessive swelling.
  • Prevents corrosion in metal brake system components.
• Testing and Compliance:
  • Detailed testing procedures for boiling point, viscosity, water content, low-temperature operation, compatibility, and simulated service performance.
  • Requirements for corrosion resistance, anti-wear properties, and shear stability.

Applications

ISO 7308:1987 provides tangible benefits for manufacturers, suppliers, and vehicle operators:

• Automotive Industry: Ensures that petroleum-based brake fluids are compatible with the latest materials in vehicle brake systems, promoting consistent braking performance.
• Brake System Manufacturing: Offers standardized criteria for selecting and approving brake fluids during design and production of hydraulic brake systems with stored-energy mechanisms.
• Aftermarket and Maintenance: Serves as a reference for workshops and service centers to choose compliant brake fluids for optimal safety, particularly in vehicles using synthetic rubber seals.
• Regulatory Compliance: Used globally to establish regulatory frameworks and industry best practices regarding automotive brake fluids, supporting vehicle safety and reliability.

Not for Arctic Use

The standard explicitly excludes use in arctic conditions, emphasizing the importance of selecting fluids tailored to environmental requirements.

Related Standards

ISO 7308:1987 is closely linked to several other international standards for quality assurance and compatibility:

• ISO 1817: Rubber, vulcanized - Determination of the effect of liquids
• ISO 3104: Petroleum products - Determination of kinematic viscosity
• ISO 3405: Petroleum products - Determination of distillation characteristics
• ISO 48: Vulcanized rubbers - Hardness determination
• ISO 7309: Road vehicles - Hydraulic braking systems - Reference petroleum base fluid
• ASTM D 892: Foaming characteristics of lubricating oils
• ASTM D 2266: Wear preventive characteristics of lubricating greases
• ASTM D 1744: Water in petroleum products (Karl Fischer reagent)

Using these related standards together with ISO 7308:1987 enables comprehensive testing and assessment for brake fluid qualification, ensuring all regulatory, performance, and compatibility requirements are satisfied.

Keywords: ISO 7308:1987, petroleum-based brake fluid, hydraulic brakes, stored-energy systems, road vehicles, brake fluid compatibility, brake system performance, international automotive standards, safety, rubber seal compatibility, viscosity, corrosion resistance, brake fluid testing.