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 Post subject: Synthetic Brake fluid?
PostPosted: Sun Nov 24, 2019 4:33 pm 
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Is Synthetic Brake fluid good for our brake systems like synthetic oil is good for the engine? Or are there any pitfalls to using it?

Thanks

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PostPosted: Sun Nov 24, 2019 4:39 pm 
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I have used it before.

I am no expert but i think there are no downsides. It mixes with mineral fluid.

For hard driving etc.. i think that the dot rating is more important rather than synthetic vs mineral based.

Greg

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PostPosted: Sun Nov 24, 2019 5:37 pm 
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I just read that it is all "synthetic" and the 5 or 5.1 is silicone based. Maybe that is what was stuck in my mind. I was thinking one of them was not hard on the paint!

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PostPosted: Sun Nov 24, 2019 6:40 pm 
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The silicone based ones do not eat paint.

The Synthetic Based Dot 3/4 Stuff might still do that. easy enough to try it out on some painted scrap pieces.

Greg

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PostPosted: Mon Nov 25, 2019 5:28 am 
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Rick Covalt wrote:
I just read that it is all "synthetic" and the 5 or 5.1 is silicone based. Maybe that is what was stuck in my mind. I was thinking one of them was not hard on the paint!


Yes, the synthetic is better, but its more expensive.

Seriously, its all synthetic.


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PostPosted: Mon Nov 25, 2019 8:20 am 
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DOT 5 is silicone based and incompatible with DOT 3/4.

DOT 5.1 is glycol based and can be mixed with DOT 3/4.

For a performance application, I just go by the "wet" boiling point. I live in the swamp and don't like throwing away half empty bottles every time I bleed the brakes.

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PostPosted: Mon Nov 25, 2019 9:04 am 
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Quote:
I just go by the "wet" boiling point. I live in the swamp and don't like throwing away half empty bottles every time I bleed the brakes.


Thanks, Can you explain that a bit more?

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PostPosted: Mon Nov 25, 2019 9:33 am 
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Brake fluid is hydroscopic meaning it absorbs water so in theory when you break open a sealed, new container it will absorb moisture from the atmosphere. So frank throws away his 1/2 open bottles of fluid to be sure he has fresh, not moisture contaminated fluid for fighting against the cosmonaut 64 darts at the lemons races.


some additional info for your and my matriculation on the topic...

https://www.wagnerbrake.com/parts-matte ... fluid.html

https://www.wilwood.com/techtip/techbrakefluidtip


Greg

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PostPosted: Mon Nov 25, 2019 9:38 am 
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Well, I actually don't do that because I'm a cheap SOB and our brakes are big enough to never boil the fluid. But that's why I always look at wet boiling point rather than dry when comparing fluids. Wet boiling point is a lower number; it represents the boiling point of the fluid when fully saturated with water (I think).

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PostPosted: Mon Nov 25, 2019 3:57 pm 
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I put the cap back on the brake fluid bottle so I don't have to worry about it absorbing water...……….

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PostPosted: Mon Nov 25, 2019 4:38 pm 
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Sounds like Silicone doesn't harm paint and has a spongy pedal?? :?

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PostPosted: Tue Nov 26, 2019 1:31 am 
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I have always steered clear of silicone DOT 5 because it can allow pockets of pure water that can corrode the system, AND you have to completely bleed out all of the normal brake fluid, AND they do not mix. If I cannot buy it anywhere and have it be easy to use, I will not bother with it. DOT 3 and 4 these days are really good, unless you are doing pro racing or something. Similarly, I once bought a car with Evans coolant, and swapped it out (after quite a bit of it leaked) because you cannot buy it on the road and you cannot mix it with water or regular coolant.

Lou

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PostPosted: Sun Feb 09, 2020 7:42 am 
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Last summer during installation of four wheel disk brakes from DR Diff, the instructions with ether master cylinder or brake calipers, I don't recall which, stated; "do not use synthetic fluid."

The warning on brake fluid not to use previously opened cans I could never understand. Generally when bleeding brakes it is done in a dry garage, cap off of can for a few seconds during MC refill, and replaced until the next top off; last thing I want is engine compartment baptism by Dot-3. If that open container can absorb enough moisture to be unusable, how is it an open master with perhaps 10 sq inches of exposed fluid is still safe to be used? The assumption here is all that exposed surface area of MC in relation to a 5/8" opening in a tightly capped bottle while bleeding would absorb much more moisture.

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