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Re: Silicone brake fluid revisited
Posted by: 4carbcorvair ()
Date: December 17, 2017 06:27PM

I've been experimenting with DOT3 SYNTHETIC. Not much of a pedal feel difference with Napa brand DOT3/4. The Prestone synthetic DOT3/4 seems to give a better pedal feel. I did a complete flush with it after replacing a one year old wheel cylinder that stuck on me. It's been in the truck for about a month now, ABS activation seems a little smoother and ABS motor sound a bit quieter. I also sucked out the master on wifeys 2000 SSei and filled with the Prestone, better pedal feel already. I'll have to do a flush on that too with the yellow bottle.

Southern Maine.
66 Corsa Convertible, 140, 4sp.
65 Monza Convertible, 110, PG.

It doesn't leak, it's marking it's territory.

A mirror is a reflection of the miles travelled.

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Re: Silicone brake fluid revisited
Posted by: jmaechtlen ()
Date: December 17, 2017 09:13PM

The Toy sat for 25 years with Dot 3 in it. I just cleaned out the M/C and continued using it. I think I gave the front wheel cyls new cups and boots.
So nothing terribly devastating. I may have done the brakes a few years before parking it - pretty sure I'd done the M/C anyway.
I did give the M/C new innards a couple of years ago - the stuff from 1977 finally gave up.

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Re: Silicone brake fluid revisited
Posted by: jmaechtlen ()
Date: December 17, 2017 09:23PM

from the linked article:
The original DOT 5 fluid specification was expected to be fulfilled by silicone based (SSBF) composition. It was designed for use in applications where its resistance to water absorption (and therefore low corrosion) was desired - like in military equipment. .... unfortunately, these characteristics were only achieved by unacceptably high compressibility. As such, the DOT 5 grade SSBF is of little value to any conventional automotive or high performance application.

It goes on to describe DOT 5.1 which doesn't have the compressibility problem.

"There are no DOT 5.1 brake fluids that exceed the dry and wet boiling points of the best of currently available DOT 4 racing brake formulas. They do meet the lower viscosity specifications, however. "

Does not sound like it is worth the trouble, unless you need racing temp performance with low viscosity?

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Re: Silicone brake fluid revisited
Posted by: jastranc ()
Date: December 18, 2017 07:37AM

In answer to Jim Stukenborg question of how my 69 ran at top of Pikes Peak Ok going up and after being at top for say hour it didn't start at turn of key.Took a little to start but let say my 69 Monza?Corsa is a 180 turbo.So they are a little harder to start in conditons like that.I might add I only run an electric fuel pump and nothing else
Coming down I used the brakes fair amount BUT also downshifted to lower gears.Like I said not issues for me.
I would have tried race up but got behind a camper so that took care of that.
Jim Stranc

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Re: Silicone brake fluid revisited
Posted by: MtnVairMike ()
Date: December 18, 2017 08:50AM

vairmech Wrote:
> BorondaFarmRacing Wrote:
> --------------------------------------------------
> -----
> > Looks like a good test, but I do have a couple
> of
> > questions. What is the vapor pressure of
> silicone
> > fluid? If you did the same thing with
> gasoline,
> > wouldn't you get bubbles even though there was
> no
> > air trapped in the gasoline? Could the bubbles
> be
> > vaporized silicone, rather than entrapped air?
> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
> Without looking it up I can tell you that the
> vapor pressure of DOT 5 brake fluid is WAY higher
> than any gasoline, other than aviation fuel
> maybe.
> For those of you out there that swear the DOT 5 is
> what you use, good for you. Personally I don't
> like the feel of the pedal after installing it.
> Yes there is a difference in pedal feel. With the
> DOT 5 fluid I cannot control the amount of braking
> modulation in the race car.
> Now the question, does moisture get into the brake
> system when using DOT 5 fluid? The answer is STILL
> yes. It just doesn't mix with the fluid.

The water just falls to the lowest point in the system, the cylinders/calipers and hangs out there. No chance of any damage...eye rolling smiley

1966 Monza Convertible, 140HP-4 speed, Ermine White

Others in the menagerie...
72 Corvette Stingray, 58K miles, owned since 86
72 MGB, 112K miles, bought from original owner in 09
78 Chevy pickup, 124K miles, bought new in 78
93 Corvette, LT1/6spd, 210K miles, daily driver since 96

Edited 1 time(s). Last edit at 12/18/2017 08:51AM by MtnVairMike.

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Re: Silicone brake fluid revisited
Posted by: Jim Stukenborg ()
Date: December 19, 2017 03:40PM

Jim Stranc, Thanks for the reply. Good to know. I wonder how a non turbo would do? Jim

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