Re: <Misc> Brake Fluid

[Richard Welty <rwelty@xxxxxxxxxxxxxxxxxxxxxx>]

At 02:19 PM 8/11/98 -0400, Anthony Dusovic wrote:
>Everything that I have heard about Silicon fluid is exactly opposite in
>regards to pedal feel and compatibility with brake systems where standard
>fluid was used.  Does anyone have more information either way.  I agree that
>it does not absorb moisture and does have a higher boiling point, but I have
>heard that the brake pedal actually gets softer and it sometimes goes to the
>floor at the most inopportune times???

well, let's see...

it doesn't absorb moisture. however, moisture still gets into braking
systems; the next question is -- if it doesn't adsorb into the brake fluid,
where does it go? the answer is that it pools up in low spots, and
continues to boil at 212 degrees F, which is only an issue if it manages to
pool inside a caliper.

dry boiling point is another issue. traditionally we focus on boiling point
because traditional brake fluids turn compressible when they boil. silicone
fluids have higher boiling points, but they turn compressible at lower
temps than they boil at. thus, you can't use dry boiling point as a measure
of when the fluid turns compressible if you use silicone.

finally, silicone fluids are hard to pour without getting bubbles in them.
this is not much help at getting good pedal feel.

i'm using motul racing fluid in my race car; i've always used the ate or
castrol lma in street cars. if the car was dual purpose (street/track),
then i used one of these two and changed it out several times a year (back
when i did a lot of track events, this could approach monthly.)

richard

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