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Brake Fluid - DOT3, DOT4 or DOT5.1

Hijinx

Hijinx

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Wondering what everyone is using for brake fluid. Rebuilding my system with stainless steel lines, dual diaphragm 8" booster and Wilwood Tandem M/C Kit with Bracket and Proportioning Valve ...

Was thinking of using DOT 5.1, would there be any issues?
 
If you've been using DOT 3 or 4, then 5.1 will not be an issue. They're compatible with each other, with 5.1 having a higher boiling point similar to DOT 5 silicone fluid.
 
Well not using anything right now, rebuilding all of it (booster, master, calipers, etc) so it's empty... thinking DOT 5.1...
 
Wilwood voids warranty on DOT5... most likely going to go with DOT5.1...
 
Hijinx said:
Wilwood voids warranty on DOT5... most likely going to go with DOT5.1...
Click to expand...
Wonder why? There's that theory that dot will swell rubber that had been in dot 3.

I put a old rubber cup out of one of my chargers for 3 months, no change

I have converted 3 cars over 5 years with no issues I have yet to.meet someone that has had an issue, but you never know
 
Dot 5 silicone won’t eat paint, yes, however it can be known to make the pedal feel a bit spongy. Yes it doesn’t absorb water, but condensate will still occur and instead of being absorbed by the fluid one would think trapped little droplets of water could be strewn randomly throughout the system...?

I use 4. Higher boiling point than 3, and also compatible with 3 and 5.1
 
4mulas said:
Dot 5 silicone won’t eat paint, yes, however it can be known to make the pedal feel a bit spongy. Yes it doesn’t absorb water, but condensate will still occur and instead of being absorbed by the fluid one would think trapped little droplets of water could be strewn randomly throughout the system...?

I use 4. Higher boiling point than 3, and also compatible with 3 and 5.1
Click to expand...
It's worse than that. The water which isn't absorbed will trickle down to the lowest point, often being the calipers. Since water has a much lower boiling point than brake fluid, it's more likely to flash into steam and cause a vapor lock. Bleeding the low points every few weeks will take care of the problem though.
 
Unless i hear otherwise that 5.1 is bad... think i'm going with that one... i have no fluid in the system at all... everything is new... so it should work out well...

This is what Wilwood says about DOT5
"... Wilwood does not recommend using DOT 5 fluid in any racing applications. DOT 5 fluid is not hygroscopic, so as moisture enters the system, it is not absorbed by the fluid, and results in beads of moisture moving through the brake line, collecting in the calipers. It is not uncommon to have caliper temperatures exceed 200 degrees F, and at 212 degrees F, this collected moisture will boil causing vapor lock and system failure. Additionally, DOT 5 fluid is highly compressible due to aeration and foaming under normal braking conditions, providing a spongy brake feel..."

But you have to wonder because they sell it on their website... go figure.
 
Here goes: Wildwood makes parts for racing applications. In racing applications
the calipers can reach these temps but in your street driver you will never reach
those temps. If you feel like using other fluid, I understand, but 5 is the only
one that does not have an affinity for moisture.
 
Been running DOT5 in my Car for a couple years with no problems at all - ran it in my clutch and brake system with my hydroboost... no problems --
 
I just bought a whole new brake system for my current project from Dr. Diff and asked him what he uses. Dot 4 was his recommendation.
 
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