This recommended practice was prepared by the Motor Vehicle Brake Fluids Subcommittee of the SAE Hydraulic Brake Systems Actuating Committee to provide engineers, designers, and manufacturers of motor vehicles with a set of minimum performance standards in order to assess the suitability of silicone and other low water tolerant type brake fluids (LWTF) for use in motor vehicle brake systems. These fluids are designed for use in braking systems fitted with rubber cups and seals made from natural rubber (NR), styrene-butadiene rubber (SBR), or a terpolymer of ethylene, propylene, and a diene (EPDM).
In the development of the recommended requirements and test procedures contained herein, it is concluded that the LWTF’s must be functionally compatible with existing motor vehicle brake fluids conforming to SAE Standard J1703 and with braking systems designed for such fluids. To utilize LWTF’s to the fullest advantage, they should not be mixed with other brake fluids. Inadvertent mixtures of LWTF’s with fluids meeting SAE J1703 are not known to have any adverse effects on performance, but all combinations have not been tested. Vehicle manufacturer’s recommendations should be followed where indicated. These fluids are not necessarily suitable for use in central hydraulic or pumped systems and are not intended for use below temperatures of –50°C (–58°F). Brake fluids covered under this recommended practice are not required to tolerate water and extreme caution should be exercised to prevent accidental entry of water which might lead to brake failure. Other performance characteristics of these LWTF’s not covered in this recommended practice are discussed in the Appendix.