Hi,
My wife (who is a professional Chemist) explained the likely problems
with Silicone brake fluid to me some time ago, so this is not based on
personal experience but on scientific principle. Not being a scientist
myself, it is explained to you (as it was to me) in layman's terms!
When new rubber components are fitted into a braking system, they are
always soaked in brake fluid first. This is partly to provide
lubrication for insertion, but the fluid also causes the rubber to
swell, giving an improved seal to the cylinder bore. In theory, there is
no problem when the same fluid is used to swell the rubber as is
eventually used in the complete system, ie, if you're going to use DOT3
in your system, use DOT3 to expand the seals, if you're going to use
Silicone in your system, use Silicone to expand the seals.
The problem arises when the type of fluid is changed between expanding
the seals and filling the system. Different fluids have different
characteristics when it comes to swelling rubber. The actual Chemical
Mechanism which causes the rubber to swell in DOT3 is not necessarily
the same as that which makes it swell in Silicone. The net result of
mixing fluids in this way is that the rubber components MIGHT expand
TWICE, by the two different mechanisms. This double expansion is what
can cause the brakes to seize, effectively reducing the clearances
between seal and cylinder bore.
This is a theoretical situation, not one I have experienced myself. But
bearing this in mind, I will not be using Silicone unless I fully
rebuild a system.
I hope this is of some interest,
Cheers,
` Bill.
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/ \ William Davies
/ \ Total Triumph Enthusiast
__ __________________ __
/ \ ______ ______ / \ 1959 Herald 948 Coupe Y128
\__/ \ || / \__/ 1959 Herald 948 Coupe
| A \____||____/ A | 1960 Herald 948 Saloon Export
| = H H = | 1961 Herald S
=====U==============U===== 1964 Herald 1200 Saloon
\________________________/ 1966 Herald 1200 Convertible
| | | | 1973 Spitfire MkIV
|_| |_| 1959 Standard Atlas Pickup
|