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Thread: Brake Fluid??

  1. #1
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    Brake Fluid??

    Okay, so not in the garage under the car, but doing some shopping.

    What brake fluid is the preference? The Dot 5 silicone has a higher boiling point and does not draw moisture better for cars that set a lot (winter). Most of the literature still says to use Dot 3 or 4.

    New system, Wilwood cylinders and front calipers, Ford OE rear.

    Mark

  2. #2
    Senior Member dallas_'s Avatar
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    Street only?
    I use the Wilwood 570 degree fluid but do track the car so I like the higher heat fluid.

    I can't remember why, but I've heard NOT to use the Dot 5. Hopefully someone will chime in.
    Last edited by dallas_; 02-18-2014 at 06:06 PM.
    FFR 7123. Tilt front, BOSS 427w, Webers, 5 link, PS

  3. #3
    Moderator Funding Member Kevins's Avatar
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    Not sure there is one single answer to this. I went with ERA's recommendation and used ATE Super Blue Racing brake fluid. It is DOT 4 and has a higher boiling point than most other DOT 4 fluids. The blue color also made it easier to see air bubbles when bleeding the system and finding leaks when I was buttoning it all down. You can order it from Amazon or find it at most BMW dealerships.

    Kevin

  4. #4
    Senior Member dallas_'s Avatar
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    Directly off the Wilwood website:

    Due to the extreme operating temperatures of a high-performance brake system, standard off-the-shelf brake fluids are not recommended. Of critical importance in determining a fluids ability to handle high temperature applications is the Dry Boiling Point and compressibility.

    The Dry Boiling Point is the temperature at which a brake fluid will boil in its virgin non-contaminated state. The highest temperature Dry Boiling Point available in a DOT 3 fluid is 572 degrees F.

    The Wet Boiling Point is the temperature a brake fluid will boil after it has been fully saturated with moisture. The DOT 3 requirement for wet boiling point is a minimum temperature of 284 degrees F.

    There are many ways for moisture to enter your brake system. Condensation from regular use, washing the vehicle and humidity are the most common, with little hope of prevention. Glycol based DOT 3 & 4 fluids are hygroscopic; they absorb brake system moisture, and over time the boiling point is gradually reduced.

    Wilwood does not recommend using DOT 5 fluid in any racing applications. DOT 5 fluid is not hygroscopic, so as moisture enters the system, it is not absorbed by the fluid, and results in beads of moisture moving through the brake line, collecting in the calipers. It is not uncommon to have caliper temperatures exceed 200 degrees F, and at 212 degrees F, this collected moisture will boil causing vapor lock and system failure. Additionally, DOT 5 fluid is highly compressible due to aeration and foaming under normal braking conditions, providing a spongy brake feel.

    Whenever you add fresh fluid to your existing system (never mix fluids of different DOT classifications), it immediately becomes contaminated, lowering the boiling point of the new fluid. For maximum performance, start with the highest Dry Boiling Point available (try Wilwood Hi-Temp 570 Racing Brake Fluid), flush the system completely, and flush it regularly, especially after severe temperatures have been experienced.
    FFR 7123. Tilt front, BOSS 427w, Webers, 5 link, PS

  5. #5
    Senior Member KING Nomad Funding Member nomad's Avatar
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    Interesting Post Dallas.
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    I thought I would see more of an even split. I have only heard from one who used the Dot 5 in a Cobra.
    The info I read says the Dot 5 was developed for racing and keeps moisture from entering the system ideal for cars that set a lot. Dot 3 or 4 suggest replacement every year or two.

    " Silicone fluid does not allow moisture to enter the system, but does not disperse any that is already there, either. A system filled from dry with silicone fluid does not require the fluid to be changed at intervals, only when the system has been disturbed for a component repair or renewal. The United States armed forces have standardized on silicone brake fluid since the 1990s."

    I don't intend to track the car much, and understand it will sit more than I think. The Dot 5 seems the better choice since the system is new and dry. I did read it was not recommended in some anti-lock systems which I take to mean also some boosted system neither of which I have.

    still confused

    Mark

  7. #7
    Senior Member tarrensmith's Avatar
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    From what I can see the DOT 3 and 4 are water soluble so any moisture gets mixed into the substance while DOT 5 will not dilute the water droplets therefore areas of 100% concentration of water will form causing potential local boiling points or areas of steam.

    I would also think the droplets will cause corrosion in spots is left for some time.

    I would vote for DOT 4 and renew the fluid regularly.... but then I am not a racer.

    Tarren.

  8. #8
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    Dallas, "Wilwood does not recommend using DOT 5 fluid in any racing applications. " agree but:
    Wilwood sells high performance Dot 5 under their own label? So if not racing is it better?

    If water will not absorb and will collect in the low part of the system, all the better to get the water out with a quick bleed at the wheels. Which it does not absorb out of the air and therefore should not be any in the system anyway.

  9. #9
    Senior Member Funding Member Morris's Avatar
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    Only use Dot 3 or Dot 4 brake fluid...NO Dot 5......

  10. #10
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    Okay, I will acquiesce and return the Dot 5 I bought and get the high per Dot 3 stuff.

    Mark.

  11. #11
    Senior Member Funding Member Al G's Avatar
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    So how often do you guys change your brake fluid? I'm coming up on two years with the Cobra and wondering if I need to do this.

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