A Way to Find the Truth about Caliper O-rings and DOT-5 Brake Fluid - NCRS Discussion Boards

A Way to Find the Truth about Caliper O-rings and DOT-5 Brake Fluid

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  • Patrick B.
    Extremely Frequent Poster
    • August 31, 1985
    • 1994

    A Way to Find the Truth about Caliper O-rings and DOT-5 Brake Fluid

    The Federal standard (FMVSS 116) for brake fluid cites a 1971 SAE test (J1703b) for compatibility with rubber brake parts. However the only type of rubber tested is SBR rubber which was ubiquitous at that time for brake seals. Versions of SAE J1703 starting about 1990 included EPDM rubber as well as SBR rubber in the compatibility test. However, updates to SAE standards do not automatically update the Federal standards that cite them. There has to be a formal public rulemaking procedure which invites everly kind of objection including objections to government regulation in general. In 2010, NHTSA proposed updating FMVSS 116 with the later 2008 version of SAE J1703 which included the EPDM rubber compatibility test. But, the proposal was withdrawn in 2018.

    That leaves FMVSS 116 without a test for compatibility with the currently most common brake seal material, EPDM. It is not just DOT-5 that is not certified for compatibility with EPDM. The same SBR compatibility test is all that is required of DOT 3, DOT 4, and DOT5.1 brake fluid as well. From a material compatibility standpoint, a FMVSS 116 certification is now pretty meaningless. To complicate things a little further, there is no requirement that vehicle manufacturers use either SBR or EPRM. They are not going to do anything really stupid with brake seals, but the owner's manual is the only source of information about the correct brake fluid for a modern car.

    For aftermarket brake parts other than fluid, the only restraint is the possibility of a safety recall. If the parts are Chinesium, a maker in China does not fear a recall, but the American seller will be stuck with the bad stuff and maybe sued.

    That brings me to the question we have discussed here. The sellers of restoration brake parts warn against using DOT-5 brake fluid. Is it just legal talk or do they know the seals will fail?

    With many brake seals we don't know what the rubber is, and maybe the seller doesn't know for sure either. But with the O-ring type pistons we can buy our own O-rings and know the material if the piston seller cannot identify the material.

    My own experience with Lone Star O-ring calipers is that I bought some for my 67 Corvette and ignored the DOT-5 warning. My silicone fluid has been in them about 5 years with no apparent problem, but I have not taken them apart for inspection. I also used my silicone fluid in another 65 Corvette with Lone Star O-ring calipers with similar good results.

    Recently, just to look at it, I bought from ZIP an O-ring conversion kit (made by SS Corvette Brake Co.) with Silicone rubber O-rings for higher temperature performance. I thought maybe these red silicone rubber O-rings would be compatible for sure with silicone brake fluid, but now believe the opposite is true. I found an O-ring supplier with a huge selection and lots of technical information on their website. The red silicone O-rings they sold were rated as compatible with glycol based brake fluid but not silicone oil or grease. They had two types of EPDM rubber O-rings and both were rated compatible with glycol based brake fluid as well as silicone oil and grease. They had a compatibility chart for a very large number of liquids but silicone brake fluid was not included.

    I bought both kinds of the EPDM O-rings and I intend to perform the SAE J1703 test on them and on the silicone O-rings from ZIP. The test calls for heating the rubber samples in a jar of brake fluid at 158 degrees and at 248 degrees for 72 hours, and evaluating the swelling and change or hardness. The O-ring performance chart rated excellent compatibility as less than 10% swelling in service. I still have to research the SAE criteria.

    They silicone brake fluid I have been using has been an Dow Corning preproduction fluid from 1977 that I was given to test on a Corvette SCCA car that I pit crewed for. I will also do the material test on silicone fluid I just bought at Advance Auto Parts, so maybe the idea that DOT-5 fluid has changed over the years can be tested too.

    My guess is that the EPDM O-rings will pass the test in both kinds of silicone fluid, and that they are the same type used by Lone Star. But that is just a guess until confirmed. Other curious NCRS members may want to do this test also. Good luck fellow scientists.
    Last edited by Patrick B.; September 27, 2023, 09:28 PM.
  • Gary S.
    Super Moderator
    • February 1, 1984
    • 457

    #2
    Re: A Way to Find the Truth about Caliper O-rings and DOT-5 Brake Fluid

    Great post Pat. I bought a 66 vette in 2017 that sat 41 years and use as my driver. I did a complete brake job then with new brakes lines, new dual master cylinder and new O-ring brake calipers all from Lone Star. I pressure bled all with Cartel Dot 5. I now have over 5,000 miles on the car and nothing leaks. The car has a rock hard pedal and stops awesome good.
    Avatar--My first ever vette, owned 3X since 1977, restored 1993-2024. Top Flight Award 9/14/24

    Comment

    • Gary B.
      Extremely Frequent Poster
      • February 1, 1997
      • 7018

      #3

      Comment

      • Patrick B.
        Extremely Frequent Poster
        • August 31, 1985
        • 1994

        #4

        Comment

        • Gary B.
          Extremely Frequent Poster
          • February 1, 1997
          • 7018

          #5
          Gary Seymour posted this on Dec 30th, 2017:




          After I read that posting, I bought two quarts of Cartel. Still sitting on my shelf, unopened, in their original shipping packaging. Waiting for the day when I dare use it in my all-new, never filled brake system.

          Gary

          Comment

          • Kenneth F.
            Very Frequent User
            • September 30, 1988
            • 282

            #6
            Re: A Way to Find the Truth about Caliper O-rings and DOT-5 Brake Fluid

            Patrick,
            There is an offroad Canadian built recreational vehicle called ARGO that uses DOT5 silicone for the brake system. I called dealers who sell this vehicle but could not get details about the brake fluid or brake seals.
            Perhaps someone would know a source of information about how silicone works in these amphibious vehicles.
            Ken

            Comment

            • Patrick B.
              Extremely Frequent Poster
              • August 31, 1985
              • 1994

              #7

              Comment

              • Larry M.
                Extremely Frequent Poster
                • January 1, 1992
                • 2688

                #8
                Re: A Way to Find the Truth about Caliper O-rings and DOT-5 Brake Fluid

                Pat:

                I have researched and reported on this over the years in both this forum and the Corvette Forum C2 Section. You can search for my posts.

                The PARKER O-ring books that I have show both EPDM and SBR compatibility with DOT 3 and 4 and 5. Parker o-rings were, and probably still are, the industry standard. Parker actually provides the specific EPDM compound that they manufacture specifically for brake o-rings, which meet all DOT 3/4/5 specifications and is compatible with all.

                Military test reports that I have show no issues with DOT 5 and EPDM, but do show the possibility of issues with SBR. See attachment.

                Larry

                EDIT: Here is a link to one of my CF threads/posts..........that also contains links to various support documents and test papers. https://www.corvetteforum.com/forums...ake-fluid.html. I am retired now and have been for years, but in my earlier life I designed and built and operated chemical plants here and abroad. I used the Parker O-ring Manual constantly......as well as their o-rings in our plants. The company I worked for also made Silicone Fluids.
                Attached Files

                Comment

                • Patrick B.
                  Extremely Frequent Poster
                  • August 31, 1985
                  • 1994

                  #9
                  Re: A Way to Find the Truth about Caliper O-rings and DOT-5 Brake Fluid

                  Larry - I knew you had written about your experiments with silicone fluid, but I could not find your threads here. Could you give the date of the last post to your thread. Maybe I can find them using the date.

                  Thanks for the very good SAE paper from Aberdeen Proving Ground. That is a 1981 paper so I know people will be concerned about the possibility of a change in silicone fluid. You say the Parker handbook shows compatibility for a specific O-ring with DOT-5 fluid compatibility. Can you give us the Parker name for that material and the date of the Parker handbook.

                  Comment

                  • Larry M.
                    Extremely Frequent Poster
                    • January 1, 1992
                    • 2688

                    #10
                    Re: A Way to Find the Truth about Caliper O-rings and DOT-5 Brake Fluid

                    Pat:

                    I added a link to my post above for CF thread/post on brake fluid. There are MANY..........but the one I linked has a lot of good info.

                    Here is a link to the Parker O-ring Manual. https://www.parker.com/content/dam/P...e/ORD-5700.pdf. This manual is 2021 version.............but the ones I used over the years went back to 1970........and showed essentially the same info on brake fluids and elastomers.

                    Don't let the size of the manual scare you. See Pages 2.4, 3.16, and 7.9-7.10 for info on EPDM. Note that there are two recommended EPDM compounds: E 0540-80 and E 0667-70. You will see on Page 7.10 that SBR is listed as "insufficient data" for compatibility with DOT 5.

                    Pages 2.4 and 7.46 show you that silicone rubber is not generally compatible with silicone fluid.

                    Hope this helps and provides you with more information. If I was still working, I could probably get the company I worked for to do the compatibility tests. .

                    Larry

                    Comment

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