First things first. I said silicone brake fluid is hydroscopic. Why?
Who knows, it's non-hydroscopic. I was talking about a racing spec
brake fluid, not Dot 5 (a silicone based fluid, not quite the same
thing), which I had completely forgot existed since it has no real
advantages for passenger car use. The problem is that moisture is
introduced into the system around seals. Since it doesn't blend with
the fluid, it stays along the walls of components and initially
corrodes the surfaces. Under racing conditions, high fluid
temperatures break it down adding air bubbles to the system. Not
pleasant when braking for a hairpin at 150+. Dot 5 is better for
racing due to it's higher boiler point, but needs to be bled
frequently. I doubt autocrossing and I know street driving won't get
Dot 5 hot enough for aeration, but I'm surprised corrosion hasn't
been a problem. Dot 4 really is the best fluid for street use.
GM
-----Original Message-----
>Greg
>I am not sure why one would need to bleed brakes all the time with
Silicone.
>Although I have heard that under flat out racing silicone doesnt
seem to work
>as well as regular fluid. I havent bled my Spitfire in over 8 years
and it
>sits a lot. I believe silicone is dot 5. Pugs
>
>Also our autocrosser has not needed brake bleeding in 2 years.
>
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