Well now that Jack & Rod have come out, I'll come out of the closet too and
admit I've been using silicone fluid for 10 years of racing in my MGA.
Never, never had a single problem. I sort of quit telling people this a
while ago because everyone looks at me like I'm nuts. Now I'll just tell
them "talk to Jack & Rod, they're nuts too".
Yes, silicone fluid does have a lower DRY boiling point than glycol-based
fluids. But, going from memory, the silicone dry boiling point is higher
than the wet boiling point of glycol. So if you replace your AP550
frequently, that's great ... but if you stick some old DOT 3 fluid in the
racecar and leave it in there all summer, you probably have a lower boiling
point than silicone fluid (silicone doesn't absorb moisture so it has no
"wet" boiling point).
That said, my MGA has 4-wheel drum brakes (yes, some of us keep the front
drums and they actually work pretty well for most vintage drivers of limited
braking ability). I would be more cautious of silicone in a disc-braked
car, because I think they probably transfer more heat into the brake fluid
(large piston area/lots of fluid volume very near the disc). Also cars with
more top speed capability, which might put more heat into the brake fluid.
Or cars with wider tires, which may be able to brake harder (I'm
contact-patch limited with 5.00-15 Dunlops).
So all I can say for certain, is that silicone doesn't boil in a 4-wheel
drum-braked skinny-tired MGA, even at circuits with heavy braking, albeit
with an amateur foot on the brake pedal. BTW, the pedal is NOT rock-hard,
but that never bothered me.
Your results may vary ... but I have certainly never had any seal swelling,
leaks, brake hang-up, etc etc that some people have ascribed to silicone
fluid. I will go back in the silicone closet now.
Mark Palmer
>From: JWoesvra@aol.com
>Reply-To: JWoesvra@aol.com
>To: RodsINTOMG@aol.com, roger.j.karnopp@lmco.com,
>vintage-race@autox.team.net, Bakeryoung@aol.com
>Subject: Re: Datsun 510
>Date: Mon, 18 Jun 2001 20:33:54 EDT
>
>In a message dated 06/18/2001 7:49:44 PM Eastern Daylight Time,
>RodsINTOMG@aol.com writes:
>
><<
> I have heard all the excuses for why silicone brake fluid won't work on
> _________ fill in the blank kind of car. In just about every case,
>something
> else is wrong, not the brake fluid. >>
>
>Take it to the bank!
>
><<, Any car
> worth keeping is worth changing over to silicone brake fluid.
>
> I have never had a piece of rubber swell up. In fact silicone is a
>rubber
> preservative, so your rubber parts should last longer. If the rubber
>came
>into
> contact with hydrocarbons like: oil, solvent etc, that is what caused the
> swelling.>>
>
>Silicone WORKS. If it doesn't then, like Rod says "something else is
>wrong".
>
>It has work for me in all kinds of "vintage" race cars. Formula cars,
>Minis,
>various small-medium bore production cars.
>
>Most people with big, fast cars use AP550 or 650 and swear by it. They
>bleed
>every day or every session. But.... I still swear by silicone in my race
>cars.
>
>With silicone, once you get the air out you don't bleed until you sense a
>problem. We get nice hard pedals with real nice feel. If you don't get that
>then don't blame the fluid.
>
>
><<Rod Schweiger
> MGB #119>>
>
>
>Ditto, Jack Woehrle
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