BRAKE FLUID / 4.0 / 5.0 / 5.1 what to use ? WHY

Discussion in 'Touring Models' started by joeythecheez, Aug 24, 2009.

  1. joeythecheez

    joeythecheez Account Removed

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    Why use 5.1, Why not ??
    I was told "stay away from 5.0 Why ??
    like I said, What and why, ( and be convincing )
     
  2. glider

    glider Veteran Member

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    DOT 5.1 is glycol base as is the DOT 3&4 while DOT 5 is silicone. They do not mix and will cause gel like pellets in the brake system that will render it inop. Dot 5 is paint friendly while the others will do damage to the paint.

    You should ONLY use what is specified on the cap or in the manual for your system.

    If you need any more on the subject or need to be "convinced" , look through the self help forum under brakes or try a search on the subject.

    Brakes, Tires and Wheels - Harley Davidson Community
     
    Last edited: Aug 24, 2009
  3. joeythecheez

    joeythecheez Account Removed

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    Thank you Sir
     
  4. fin_676

    fin_676 Experienced Member Staff Member Moderator Contributor

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    The dot rating on brake fluid i think refers to the boiling point of the brake fluid the higher the number the higher the boiling point
    for many years silicon based brake fluid had a higher temperature rating than glycol based fluid and was used in many racing applications and was also specified for HD motorcycles
    but with the introduction of dot 5.1 brought glycol based fluids to the same temp rating as silicon fluids
    glycol fluid compresses less than silicon and is required for abs systems

    but your service manual/brake reservoir cover will specify the correct fluid for your bike

    Brian
     
  5. Caper

    Caper Active Member

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    I don't know why someone would say "stay away from dot5" your 04 bike uses dot 5, it's paint friendly and works well, unless you want to do a complete purge and clean of the entire brake system, I'd stick with what the bike came from the factory with, sudden brake failure is not something I'd want to gamble with.
     
  6. NEWHD74FAN

    NEWHD74FAN Experienced Member Retired Moderators

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    Quite simply use the proper fluid recommended for your specific year and model bike. Yes you can go from DOT3 to DOT 4 and take advantage of the higher boiling point, but that is about it for interchangeability.

    If you use the wrong stuff, latent defect means piston seals, hoses or o-rings are contaminated and brake failure may not occur immediately but very likely fail while your on the road. Read what the brake reservoir cover AND the service manual recommends. Be Safe Out There!
     
  7. dhorne

    dhorne Active Member

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    Good to know all this info and I mixed 5.0 and 5.1 , now do I have to take the whole system apart and clean it or can i flush it a few times with 5.0
    thanks in advance
     
  8. fin_676

    fin_676 Experienced Member Staff Member Moderator Contributor

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    If it were my brakes and my life at stake id strip the whole brake system and thoroughly clean the lot before rebuilding and filling with the appropriate fluid

    Brian
     
  9. dhorne

    dhorne Active Member

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    Good point and i think I will do that
     
  10. rancid

    rancid Active Member

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    dot 5 fluid must be compatable with dot 3/4 system to get its rating, it wont affect the seal, but 3/4 dont mix into dot 5 so any 3/4 left in the system will still absorb moisture in little pockets. 5.1 is similar to dot 4 but the boiling point is much higher. if you have used 5.1, pull a bottle of 5 through to avoid any problems its cheap enough.