Max -
Q. Any brake fluid commercially available that is DOT 5 rated and not
silicone?
A. For things on the market as we speak, it depends on who you talk to
at DOT. If you talk to the safety standards people, then yes, if you
talk to the chemists, then no. As far as the safety standards people
are concerned DOT 5.1 is a subset of DOT 5.
Since the standards for DOT 5 include things like pH, they had to create
the 5.1 standard to allow for the fact that companies were making
non-silicone fluids (with a different pH) that otherwise met DOT 5
specs. (Keeps the chemists happy.)
Talk to them in a month, and the answer may be different still. There
are always new products going through the approval process and going
commercial
I didn't mean to get huffy about it, just trying to be clear. (You
should SEE me when I get huffy!) <grin>
As for compression of liquids, Bill Loubiere sent this reference to
refute my statement. I think it makes my point.
http://www.chem.lsu.edu/lucid/subjectinfo/liquids.html
About a third of the way down the page, it lists the "Properties of
Liquids". It shows the compressibility of Liquids as "Almost Zero".
Note that this is the same as for Solids. As an engineer would say, for
all practical purposes, liquids don't compress. They certainly don't
compress at the pressures developed in a brake system. If your pedal
feels spongy, it's either air, or your hoses are ballooning, or some
other mechanical factor is creating "give". It isn't SBBF compressing.
On the condensation of water, particularly Stuart MacMillan's
experience, I've put 5 years on my system with SBBF with no problems.
I'm seriously interested in exploring the different experiences to
determine what's going on. I'm wondering if there is an issue regarding
the specific gravity of different brands. (Specific gravity is not part
of the specification for DOT 3, 4, 5, or 5.1 that I can find, so it may
vary between brands.) If one brand has a specific gravity slightly
greater than water, and another slightly less, that could make all the
difference in the world.
Chris K.
P.S. I'm on the Digest, so there's a bit of a "lag" on my end of the
conversation. Bear with me.
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