<VV> Corvair Master cylinder

[jvhroberts at aol.com]

Actually, conventional brake fluid is a decent lubricant, and it's a glycol, not an alcohol. The reason for the silicone grease to assemble parts is purely on the basis of compatibility with the rubber components. 

My only two gripes with silicone brake fluid are:

1. IT has about twice the volume compressibility of glycol fluids, and at least on modern disc brake systems, makes for a noticeably spongier pedal. On?a Corvair stock brake setup, the pressures are relatively low, and more importantly, so is the fluid volume in the lines and cylinders, as compared to a car with disc brakes. 

2. In modern cars with ABS, silicone fluids are notoriously awful metal lubricants, and they WILL destroy ABS pump assemblies. 


-----Original Message-----
From: Chris & Bill Strickland <lechevrier at earthlink.net>
To: virtualvairs at corvair.org
Sent: Fri, 16 May 2008 3:00 pm
Subject: Re: <VV> Corvair Master cylinder



Concerning DOT 5 (silicone) brake fluid:

My big complaint with the non-silicone fluids is that, in spite of 
manufacturers claims to the contrary, they are not a lubricant (since 
when is alcohol a lubricant?).  Especially after they have drawn in some 
moisture.  Those little packets in some overhauls kits -- silicone based 
brake assembly fluid (included because brake fluid is NOT a lubricant), 
ala Raybestos #BAF-12 Hydraulic Brake Cylinder Assembly Fluid (Carquest 
#TBAF 12) -- 
http://www.autoparts2020.com/rsdev/part_detail.jsp?PART_HDR_ID=40378&cat=2,3,4,5,9
Also works well on assembling the fuel filler tube to gas tank hoses.

Now, I am not going to reccomend that you use silicone for racing 
applications -- DOT 5.1 type fluids are superior -- but I have used 
sisicone DOT 5 for a number of years, including in my bug-eye Sprite, 
which sits for years at a time. Previously, with conventional fluids, 
everytime I would want to move / use it, it meant overhauling the clutch 
and brake systems, even though I'd be using "proper" British fluid, and 
sometimes they wouldn't work even while you were actively driving them - 
damned English "rubber".  With the silicone fluid, they work everytime, 
even after long periods of storage.

I also use silicone in my daily driver Fieros, because the aluminum 
stepped master cylinder design is subject to physical wear without the 
improved lubrication of of the silicone fluid. Both in flushed systems 
and in unflushed systems.  Mixing of the two types produces some ugly 
mixtures, but the evidence, to me at least (I haven't had a braking 
failure), is that they work in daily driven scenarios in spite of 
appearences and foreboding naysayers.

I have not experienced the supposed "compressability issues" some have 
mentioned -- maybe they just don't know how to bleed brakes and blame 
the fluid -- I don't know -- but I do not find it an issue in mine or in 
any other car (hot rods with fancy expen$ive paint jobs) I've worked 
on.  Did I mention it won't eat up your paint?  And, although it does 
not absorb moisture like conventional brake fluid, neither does it suck 
it out of the atmosphere to the point of fluid failure due to 
contamination.  Yes, either type of fluid should be changed every couple 
years, and, if you get right down to it the whole system should be 
overhauled at the same interval -- whatever gives you peace of mind ...

And, back to the main topic, yes, I endorse a dual system master 
cylinder -- between us, both my wife and I have had a brake hose failure 
(one once an FC - wife) and they tend to provide more excitement in 
one's life than the most thrilling carnival ride.

Godspeed & goodstopping,

Bill Strickland
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