I'm trying to figure out where I have had this feeling before. It is like I have been here but I am certain I haven't. So weird...

 

Nah. I know my car.

 

Surprised no one has mentioned this. My recollection is that some of the 600 degree fluids, like AP 600, are a borate ester formulation which is not compatible with glycol ester used in conventional DOT 4 fluids and AP 551. I am not sure of the process for purging glycol from a system before using the borate type. For a street car, I would want to consider the hassle.

For my own use, I've found that AP 551 works just fine at the track, without boiling etc. It is also a lot cheaper than the big boy products. (AP has rebranded their products and so these names have changed.)

 

So, you say you have a better pedal with "Endless". and now you "know your car" so that's your validation that endless is providing the "better pedal".
Ive heard that more than a few times before..... you always know your car, until you don't.
And actually, you might know your car, but you might not know the bleed process error or variability possibilities.... unless you are perfect in that area too.

So, what do you think is causing the different (feeling) or "knowledge" in your case..... do you really think there is a compressibility difference, enough to feel??

 

Im using Wildwood EXP 600. it has a 600 degree dry boiling point and a 400 degree wet boiling point. DOT4 (which is pretty good... near dry boilng point of SRF, but down from its 500 degree wet boiling point)
It wasn't too expensive.. I think 25 bucks a bottle at the track.

I noticed the pedal felt so much better when I changed from Wesson Oil, and before that , Olive Oil.
when I cook my brakes, I don't feel as hungry during the race anymore.

 

Keep in mind that the current DPT 5.1 brake fluids have as high of a boiling point than the silicone-based DOT 5 brake fluid, and, because it is glycol based, it is both hygroscopic (disburses moisture) and provides a firmer brake pedal than silicone. Some 5.1 brake fluids report even higher than silicone boiling points.

Reference: http://en.wikipedia.org/wiki/DOT_5.1

Just make sure the can stays closed on your shelf, and the system on your car stays sealed, because hygroscopic fluids do absorb/draw moisture out of the air.

To that: replace the seal under your brake reservoir cap (which is vented) with a bellows-type seal, so air cannot get to the brake fluid in your reservoir. Here is one:
http://www.928motorsports.com/parts/...er_bellows.php

 

Actually, it seems that the DOT 5 has the same boiling points as some of the DOT 4 fluids, but again, is corrosive to internal DOT 4 designed systems. DOT 5.1 seemed to get rid of the slight compressibility issues (1.5% more compressible, or less than .5mm on a pedal stroke) but lowered the boiling point numbers. Also, don't be misled by dry boiling points. Its well known that once the bottle is opened, you basically need to refer to the wet boiling points as a point of reference. I think that was all covered on one of the links Matt had provided in the beginning.

so the bottom line is there is no need to use a DOT 5 in our systems designed for DOT4 and there are a lot of racing fluids with high boiling points... the only real differences might be in their viscosity, how the fluid acts In the system, and/or how difficult it is to bleed them, as well as how they absorb moisture.

 

We no need no stinking brakes. We drive flat out. but I like speedbleeders & Endless :-)

 

yep, that's how you keep the brake fluid from boiling! I use olive oil now!

Oh, but endless gives you a better pedal!