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Brake Fluid

Discussion in 'Norton Commando Motorcycles (Classic)' started by Onder, Dec 5, 2018.

  1. Onder

    Onder

    Joined:
    May 11, 2010
    From Andover's monthly newsletter:

    Brake Fluids: A warning from Ashley

    This is what happens when you use a ‘’DOT 4 Compatible brake fluid’’ the master cylinder diaphragm does not fit the cap! The fluid from Fuchs Silkolene is no longer available – did they know something?
    We advise against modern brake fluids because the seals in 1970s brake systems generally do not bear modern type (DOT 5 etc) brake fluids.

    Well any comments on this? Do I risk 5.1 instead of 4? I assume he means 5.1 as
    5 is totally incompatible.
     
  2. jaydee75

    jaydee75

    Joined:
    Jul 2, 2012
    I go against the grain and use all Dot5, silicone based, should not be a problem with elastomers. I like it because it does not attract moisture and corrode stuff. Got it in all my bikes.
    Flame on?
    Jaydee
     
  3. Onder

    Onder

    Joined:
    May 11, 2010
    I too use 5 in one of my bikes but now Im doing a flush and refill on one that was filled with 3 or 4 and so that precludes 5. Im wondering
    if I can go to 5.1 or am I courting disaster?
     
  4. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
    "DOT 4 Compatible brake fluid".
     
    MexicoMike likes this.
  5. Onder

    Onder

    Joined:
    May 11, 2010
    AN says that compatible isnt the thing or so it seems to my reading of it. My question is are they correct or is it compatible as manufacturers claim. It would
    seem to me that the fluids may well be compatible but the seals, due to age etc
    would not be.
     
  6. Deets55

    Deets55 VIP MEMBER

    Joined:
    Oct 3, 2013
    DOT 3, 4, and 5.1 are shown to be forward and backward compatible. I have been using Motul 5.1 for at least 3 seasons in both my Norton and Honda with out any problems. Prior to that I would use and mix 3 and 4 depending on what I had around the garage and never had an issue. Replacing the fluid every year is the best practice, only takes a couple of minutes to do on a property functioning system, and moisture shouldn’t be an issue anymore.

    Does anyone still have original seals from the 70’s in their systems anyway?
    Pete
     
  7. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
    To be "DOT 4 compatible" would suggest it must be something other than DOT4?

    Unless we are only getting half the story?
     
  8. Madnorton

    Madnorton

    Joined:
    Jun 9, 2008
    The photos were in the news letter emailed out, Dot 4 brake fluid is exactly that, DOT 4 Compatible is not, there have been a few cases where DOT 4 compatible fluid has been used, it causes the seals to swell to over a third normal size. The person that found this out had bought our seals thinking that the competitors offerings he originally bought were faulty, ours reacted the same. Not sure where the likes of Fuchs Silkolene were going with this product, but with DOT 4 being so cheap it seemed a pointless offering. If anyone wants to see the photos, to contact me at work.
     
    NortonMKIIA850 likes this.
  9. cliffa

    cliffa

    Joined:
    May 26, 2013
    Madnorton, Thanks for clarifying. I received the newsletter too, and to be honest couldn't understand what was being said.


    Cheers,

    cliffa.
     
    NortonMKIIA850 likes this.
  10. kommando

    kommando

    Joined:
    May 7, 2005
    Dot 5.1 is backward compatible with Dot 4 and 3, is Dot 5.1 an issue.
     
  11. Madnorton

    Madnorton

    Joined:
    Jun 9, 2008
    No, not that I have heard, because I assume it is DOT 5.1.

    I still have some fluid here at home, I will soak a diaphragm and just see how big it gets.

    I tried to query what exactly DOT 4 Compatible fluid compared to DOT 4 was and met with cagey responses. The container only says 'DOT 4 compatible' not 'DOT 5.1 also compatible with DOT 4' like some of the above have stocks of, ie what you actually have and what it is compatible with as a description.

    When someone rings and says the diaphragm seal does not fit, I imagined someone trying to fit it to a Grimeca or other M/C, considering how many are sold and then suddenly one does not fit, seemed really strange. There were a couple more cases outside the UK that Norton owners experienced, and some in other non Norton motorcycle applications that had noticed it, I also queried some other brake part manufacturers, their reply was they could not see what a 'DOT 4 Compatible' description would mean other than it is not the correct DOT 4.

    At the time, I looked around for the product and it was still available from OPIE, but not Fuchs Silkolene directly (who did not reply) so must have been leftover stock, there were other manufacturers listing 'DOT 4 Compatible' with no other DOT X.X etc on the container other than the company mentioned here. Even worse I could not find any in the 4 wheel world, just ordinary DOT 4. It seems this stuff was targeted for some strange reason at motorcyclists. There was a considerable price difference on it to, make your own minds up on that one.

    Personally, I use cheapo DOT 4 stuff from Comma Oils, feel free to use what you like but it must be compatible with the seals, if you use a mix of components, Grimeca, AP or Brembo, then they may all have different oil specs, it would be rare as DOT 4 is still widely specified by most manufacturers.
     
  12. cliffa

    cliffa

    Joined:
    May 26, 2013
    Personally I think the main thing is to change it annually, or more often. This was a caliper I recently overhauled...



    As you can see It was totally blocked with emulsified brake fluid. I had to boil it and use drill bits to clear the passageways.

    Cheers,

    cliffa.
     
  13. batrider

    batrider

    Joined:
    Aug 9, 2008
    Nonsense. Dot 4 is fine. You don't want the Dot 5 silicone fluid.
     
  14. Fast Eddie

    Fast Eddie VIP MEMBER

    Joined:
    Oct 4, 2013
    Why not?
     
  15. MexicoMike

    MexicoMike

    Joined:
    Jan 31, 2010
    Per recent research, I found this (summarized) info in multiple sites concerning brake fluid:

    Dot 5 does not mix well with Dot 3, 4, or 5.1 and it can aerate when used in ABS system so it is not recommended for ABS systems - though that has no impact on our Nortons. It has different characteristics than 3, 4, or 5.1 as far as the "feel" of the brakes. Many reports of it feeling spongy compared to 3/4/5.1 The only time DOT 5 should be used is if the entire (non-ABS) brake system is new and has never been filled with DOT 3 ,4, or 5.1, OR you can thoroughly and completely clean out any Dot 3/4 brake fluid that is in the system.
     
  16. RoadScholar

    RoadScholar VIP MEMBER

    Joined:
    Dec 28, 2008
    DOT 5.1 is backward compatible with DOT 3 and DOT 4. It provides no real benefit for non-ABS braking systems; it has a lower viscosity than 3 or 4 and was developed for ABS systems that could be called upon, in cold climates, to function in ABS pumps that are at ambient temp. DOT 4 is less hygroscopic than DOT 3. Flushing your brake fluid annually is excellent maintenance, exercising your calipers and changing out pads/pucks when they wear to 50% and scrubbing the disk(s) with Scotch Bright (I use the dark red) will insure the friction material gets a good shot at breaking-in without glazing.

    I am not a proponent of DOT 5 silicone based brake fluid. Yes, it in non hygroscopic. Yes, it has a much higher boiling point. But, it also comes with a much greater viscosity, it is NOT compatible with any glycol based fluids, it is harder to bleed and it will become mushy, which, in the early stages, can actually enhance brake modulation. AND, don't even think you can just bleed it in; a complete disassembly of existing glycol based systems and flushing with alcohol is required before you can install DOT 5. I have met knowledgeable riders/mechanics that swear by DOT 5, and, as most of you know, Harley specifies it in older models, and it ain't inexpensive. I believe that DOT 5 represents the extreme of "you get what you pay for".
     
  17. Atlas Commando

    Atlas Commando VIP MEMBER

    Joined:
    Feb 27, 2018
    I have a bike that specifies Dot 5 and discovered that it was actually fitted with Dot 4. I decided to put it back on spec and went through a lengthy alcohol flush (hmm, matching bike and liver...) and took it back to Dot 5. It was a Harley and most modern years call for Dot 4 so no doubt the PO or a shop made the mistake. No discernable difference in performance but then, it's an HD so what has performance got to do with anything?
     
  18. eskasteve

    eskasteve VIP MEMBER

    Joined:
    Sep 24, 2012
    Not to get off track too much but my guess on why Harley specifies DOT 5 is because the master cylinder for the rear brake is right under the front header pipe. Any moisture that would be trapped in the brake fluid could turn to steam from the heat generated by the exhaust header. Since gas wont compress your rear brake is now useless.
     
  19. MexicoMike

    MexicoMike

    Joined:
    Jan 31, 2010
    Yeah, but it's a Harley and the brakes suck anyway! ;) OTOH, I guess brakes that suck are still better than 'useless' brakes! :)
     
  20. RoadScholar

    RoadScholar VIP MEMBER

    Joined:
    Dec 28, 2008
    I think you hit real close to the 10 ring here. Harley brakes, up until recently--now Brembro, have provided some of the poorest stopping power of any device that can be called a brake. Norton OE clam shell calipers and OE masters are almost as poor, and I suspect that if Norton used cast iron they would have specified DOT 5 fluid. I believe that the Harley and Norton braking systems generated more heat than stopping power; add poor maintenance and with a DOT 3 or 4 fluid soaked with water a prolonged braking action would easily boil the fluid and could cause high pressure steam to render the system completely useless; with DOT 5 there is no water infusion, so you are left with only poor braking performance.

    Using DOT 5 in a good braking system is a user choice.