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Replacing brake fluid

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  • wildchild
    wildchild
    yesterday
    I have always used HD Dot 4 Brake fluid and looking at a change in brand, Penrite Super Dot 4.
    For those tech guys in the know will there be any issues with the ABS system and non ABS using the Penrite Super Dot 4. 

    I can do a compatibility test but this will not rule out any long term issues, interested to know if anybody has had issues with Super Dot 4.
  • B0nes
    B0nes
    23 hours ago
    Dot 4 good. Dot 5 bad, as a silly mate found out the expensive way. He thought Dot 5 would be better because the higher number and add it without a good flush of the system. Bet he won't do that again
  • tussuck
    tussuck
    22 hours ago
    Depends.... DOT4 bad in the old FXR while DOT5 is good.  DOT5 being silicone based is for older systems.  

    I think you can use DOT4 or DOT5.1 interchangeably (curses to the dickhead that thought up the 5.1 the prick) 
  • speedzter
    speedzter
    19 hours ago
    We really shouldn't confuse the topic that is about DOT4 , but what the hell.

    I am running late model Brembo touring Calipers/Master on my 2000, and I'm running Dot5 Silicone .
    I'm sure years from now when it is sold, someone will get a surprise 😁
  • Retroman
    Retroman
    18 hours ago
    DOT 5, and DOT 5 ONLY, up to 2005 ( Silicone based brake fluid, doesn't damage paint etc)

    2006 and on , DOT 4 ( or as mentioned DOT5.1) ONLY (Damages paint, just look at all the 2006 and up black front master cylinders).

    The "official" reason for why for ? DOT5 not compatible with ABS systems, even tho' it was maybe 2013 before all HD's had ABS)

    General consensus is don't mix , and don't try to change.

    I changed my own 2008, and any bikes I service for mates, to DOT 5.1 from Supercheap, bought on "specials" days.
    Mixes fine with residual DOT 4, and supposedly has advantages over DOT 4, less water absorption and more temperature tolerant.

    I use a wee vacuum pump setup, and it can be handy to have a steady handed mate to gently top off the master cylinder as you go.
  • wildchild
    wildchild
    17 hours ago
    Quoting tussuck on 08 Oct 2025 10:16 PM

    Depends.... DOT4 bad in the old FXR while DOT5 is good.  DOT5 being silicone based is for older systems.  


    I think you can use DOT4 or DOT5.1 interchangeably (curses to the dickhead that thought up the 5.1 the prick) 

    Yeah 5.1 seems a bit odd when its compatible with Dot3 and Dot4, should have been Dot4.1 which would make more sense all being compatible fluid.

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