Brake Fluid

[chjort]

Does anyone have recommendations on a brand of brake fluid to use? I'm going to be filling and bleeding this weekend. Also, how much is usually required? I have the FFR stock brakes front and rear and am using the CNC dual reservoirs. Thanks!

[Tree]

I just did this last night and this morning and went through 3 bottles, though I kept trying to bleed a system that had a bad master cylinder that we letting in air. I think that two bottles should be enough unless you run into issues. It is certainly worth the time to go around every connection you have and really tighten it down now.

As for fluid, that depends on how you intend to drive the car. If you plan to do any track days, go with a high temp fluid. Multiple fluid options that should all be fine as long as you change your fluid regularly. If you are just planning to drive it on the street, any DOT 3 fluid should work fine. No need for a high temp fluid unless you plan to track the car or ride the brakes down a mountain.

[edwardb]

For street driving, I've always used Valvoline DOT 3/4 Synthetic. Common item at most parts stores and not particularly expensive.

[NAZ]

Agree with Tree -- street car or any use that does not cause extreme heating of the calipers does not need the expensive high temp fluid. I'm not tied to a particular brand (except for my race car) but if there is one you like stay with it.

[chjort]

Tree raises an interesting point I had not considered. I'm in Denver, and definitely plan on having some mountain fun with this car. Should I go with hi-temp fluid in anticipation of mountain driving?

[Railroad]

Wilwood

[Tree]

Sorry, I was more trying to point out the extreme with my comment about ridding the brakes down a mountain. I would think you should still be fine with regular fluid as long as you are not a fool about it. Yes, you could possibly overhead your brakes if you stay on the brake pedal for long periods but with the low weight of the car, I think you would need to be pretty hard on the brakes in the mountains to boil a normal brake fluid. If you downshift going down hill and use some engine braking or if you take your foot off the brake pedal every once in a while, I doubt you would over heat a normal fluid.

The run away truck ramps in the mountains are for semi trucks that cook their brakes but that only happens when they fail to keep the truck under control by being in the correct gear and using some engine braking. The amount of weight that those semi trucks can be trying to slow down can create a lot of heat very fast and can actually glaze the brake pads and drums. Braking at it's core is transferring a car's momentum into heat. The amount of momentum that our 2500lbs cars have compared to a loaded up trailer is on another scale and standard cars don't boil their fluid going down mountains, so I think you will be okay.

There are a lot of "I think" and "should" used in there as I have never actually driven one of these cars and I have no experience other then the build process that I am still completing. I am sure some others will be able to add experience and more certainty to the answer but I wanted to respond after my initial response may have made you feel high temp fluid would be needed.

[NAZ]

Again, I agree with Tree's assessment and conclusion.

[BEAR-AvHistory]

Also am running Valvoline DOT 3/4 Synthetic.

[davekp]

All brake fluid is synthetic.
Do not use DOT 5 (silicone).

[Jeff Kleiner]

Do not use DOT 5 (silicone).

Dave,
That's what was in your chassis when it arrived. I saw the purple in the master cylinder and said "Fudge"...or something like that ;) All lines & hoses got replaced then a full gallon of denatured alcohol was flushed through followed with 2 or 3 quarts of fresh DOT3/4 before bleeding. That fluid along with a couple more items quickly told me all I needed to know about the guy who started the build and was why it got torn all the way down to the bare frame for a complete do-over!

Cheers,
Jeff

[KenWilkinson]

Why is DOT 5 Silicone not recommended?

[Jeff Kleiner]

Why is DOT 5 Silicone not recommended?

It can be and has been discussed ad nauseum. Here's a cut & paste of a response I made to the same question a few years ago:

...trust me on this---DO NOT USE DOT5. In a nutshell it is a silicone fluid and retains millions of tiny air bubbles making it compressible meaning you will never get a firm pedal. Additionally it is non-hygroscopic (does not mix with water) so any moisture will stay separated and since H2O is heavier than the silicone it will settle in the low points; i.e. calipers. Get the brakes hot, the water boils and you have no brakes! Stick with glycol based DOT3, 4 or 5.1 fluid.

Jeff

[Papa]

Chjort,

I'm near Denver and for my car I'm using simple DOT 3 fluid in my Wilwoods. Even in the mountains, you're not going to heat your brakes up to race temps unless you ride them all the way down the mountain.

Gear down and enjoy the scenery!

Dave

[NAZ]

chjort, like you and Papa, I live in the mountains (7,000' ASL) and travel in any direction is downhill. Think about it -- most of your neighbors daily drivers are quite a bit heavier than any FFR car and they don't come from the factory with high-temp racing brake fluid. They travel the same roads as you.

But if it makes you feel better to spend more of your hard earned $$ on high-temp brake fluid, I use Wilwood EXP 600 Plus Super Hi-Temp racing brake fluid in my race car. It's way more expensive than the generic parts store brand that meets the same federal standards as the all the name brands. It's your $$, spend it like you desire.

[Avalanche325]

I use Wilwood fluid also, but I do autocross regularly, and occasionally the track. My daily driver has Valvoline.

I change my fluid every year. Every other is good for a street car. Yes, you should change your fluid in your daily driver too.

Isn't it nice how DOT 5 is silicone and DOT 5.1 isn't? Just to keep it confusing.

[davekp]

Oddly, my 1990 Harley used DOT 5 (silicone) but my '08 used DOT 3. Maybe they decided the DOT 5 wasn't so good- or maybe it was just a cost saver to go back to DOT 3.

[chjort]

Thanks for all the input, guys. You're right that my daily driver doesn't require anything special to handle mountain roads, so this shouldn't either. No need to waste $$ on something that's unnecessary. Thanks again!

[boat737]

Question....

If I remember right, I read somewhere that DOT3 handled moisture better than the others. (i.e., absorbs less moisture). Anyone have any input on that?

[NAZ]

Boat, DOT-3 brake fluid is made from pure Glycol Ether and has a dry boiling point of 401F & wet boiling point of 284F. DOT-4 is a blend of Glycol Ether & Borate Ester and boiling points are: Dry 446F, Wet 311F. DOT-5.1 is also a mix of Glycol Ether & Borate Ester and boiling points are the same as the DOT-5 silicone fluid: 500F Dry and 356F Wet.

So I'd say that DOT-4 handles water a bit better than DOT-3 if wet boiling point is a critical factor. DOT-5.1 is just a bit better than DOT-4.

[Duke]

I use Motul 660 in all my performance cars, including the cobra.

[Avalanche325]

Oddly, my 1990 Harley used DOT 5 (silicone) but my '08 used DOT 3. Maybe they decided the DOT 5 wasn't so good- or maybe it was just a cost saver to go back to DOT 3.

When DOT 5 came out it sounded like the perfect brake fluid.
1. Won't hurt your paint.
2. High boiling point.
3. Hydrophobic.

Brake fluid that won't absorb water? It does't get any better than that! However, as with everything in life, nothing is free. Hydrophobic turned out to be a bad thing. A ruin your entire brake system bad thing. Everyone thought that water would just not get into the system. It turns out that it gets in there, stays undiluted, and the corrosion starts. One of those it had to get into real world use to see what didn't work situations.

[toadster]

https://blog.amsoil.com/dot-3-and-dot-4-brake-fluid-whats-the-difference/