As a side note, boiling points are measured with fresh brake fluid. As DOT3
& 4 fluid sits in your brake system and absorbs moisture, it's boiling point
drops dramatically.
-----Original Message-----
From: James H. Nazarian, Ph.D. <microdoc@apk.net>
To: Max Heim <mvheim@studiolimage.com>
Cc: MG List <mgs@autox.team.net>
Date: Thursday, February 24, 2000 9:26 AM
Subject: Re: Brake light switches AND fluid problems
>Hi Max,
>
>As I have understood, DOT 5 does have a lower boiling point than the other
brake
>fluids. The difference is not great, and falls into the vicinity (I think)
in
>excess of 400 F. Most amateur LBC racers, in their wildest dreams, will
never see
>brake fluid temperatures like that. So be it if Silicone isn't the best for
race
>cars, but it is great for street cars. IMHO it is silly to be changing
brake fluid
>once, twice or more times per year when there is a better solution
available. I
>hate to think where all that DOT 3 & 4 brew gets dumped every year.
Silicone is
>inert, non-irritating, non-toxic and, for the most part, non-allergenic. As
for the
>breast implant controversy, I prefer Coke: "It's the real thing."
>
>Jim
>
>Max Heim wrote:
>
>> Actually, I seem to recall that the knock on silicone is that it had a
>> lower boiling point, and that with hard driving and disk brakes, it could
>> potentially boil. Steam is highly compressible. For this reason it used
>> to be strongly recommended for show cars (safe for paint) and
>> contraindicated for race cars (obviously), with everyone in between free
>> to choose. Haven't heard this lately, perhaps newer formulations have
>> fixed this.
>>
>> James H. Nazarian, Ph.D. had this to say:
>>
>> >Gents,
>> >
>> >> The three problems with silicone are that,
>> >> 1. it does not absorb water. This allows water to pool in the lines
unless
>> >> you bleed it out every year.
>> >
>> >Hydrophobia is not a detraction of DOT 5, but a benefit. Can someone
site an
>> >example of definitive research showing that water will pool in silicone?
I
>> >don't
>> >think so! Try leaving some in an open graduated cylinder for a year or
two
>> >and
>> >see if the volume changes, or any pools of water show up.
>> >
>> >> 2. it is (or was in original formulation) just a bit more compressible
than
>> >> DOT 3 or 4 brake fluid. This may only be in early silicone fluids and
could
>> >> be much better now. Barney, you use that A for some serious
autocrossing.
>> >Did
>> >> you notice any difference in pedal feel between DOT 5 and DOT 4?
>> >
>> >Compressibility? Of a liquid? If such a thing could occur, I seriously
>> >doubt one
>> >could detect it with a foot.
>> >
>> >> And 3. the above seal swelling problem.
>> >
>> >I respectfully suggest this is a myth. If the stuff is no good I'd
appreciate
>> >some proof before I remove what appears to be perfectly performing, 10
>> >year old,
>> >anhydrous brake/clutch fluid, and replace it with rust-worm food.
>> >
>> >Jim
>> >
>> >
>> >
>>
>> --
>>
>> Max Heim
>> '66 MGB GHN3L76149
>> If you're near Mountain View, CA,
>> it's the red one with the silver bootlid.
>
>
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