brake fluid

[coyled]

What kind of brake fluid are you guys useing? My brake pedal seems to get spongey after or during road racing. I think the fluid is cooking. This is even after I went to a dot 5 I think, silicone based fluid. This still seems to go away. Which kind is the best? scott

[BJGreen]

Silicone brake fluid is very popular with vintage Corvette owners becasue it does not harm paint and does not absorb water, which could damage valuable original equipment brake system parts. It is also useful for cars in collections which are not driven. It is not recommended for much else.

This quoted from the Wilwood web site:
"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° F, and at 212° 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. DOT 5 fluid is best suited for show car applications where its anti-corrosion and paint friendly characteristics are important. "

[coyled]

Yes, I know it is the wrong fluid, clearly. My question is what are the race guys running in cobras for brake fluid?I am being told castrol is the best, at least thats what the cup guys are running. Any comments? scott

[RACER X #99]

Scott,
That Castrol brake fluid the pro's use costs $75.00 a qt.
Most of us part time wannabe racers use Wilwood Hitemp brake fluid or SS Brakes Hitemp fluid. Their are others not as expensive as the Castrol at around $7.00 a pt.
Cranky
BTW be careful with the non silicone fluid. A leak on my master cyl. spilled over to my fender. Result, no more paint on fender.

[coyled]

Cranky, I am far from a pro, just a rookie at best. I am going to check into the price of the castrol or I may go with the willwood. Wilwood has 2 types, like 500 degree and 600 degree, I think. Which one are you useing? If this pedal gets as sponge as it did again, I will not have a straight enough body left to worry about the paint damage from brake fluid. Thanks for your show car(wink,wink) cocerns. scott

[Andy Dunn]

Pegasus Auto Racing
http://www.pegasusautoracing.com
carries one of the biggest lines of fluid and has an interesting comparison chart

BRAND - wet boil - dry boil - dot

Castrol LMA.....311/446 dot 4
PFC z-rated.....284/550 dot 3
Wilwood 570...284/570 dot 3
AP-551............284/540 dot 3
AP-600............284/572 dot 3
and the liquid gold of brake fluid...
Castrol SRF.....518/590 dot 4

I am trying
http://www.thebrakeman.com
Brake Man Racing Fluid
BrakeMan.....300/577

[Cobra20646]

If you have the DOT5 synthetic stuff in the car now, what precautions are to be heeded when swapping out that stuff for DOT 3 or 4? I guess a complete flush would do it right? Does changing over cause any problems with the seals and other rubber parts?
- Jim -

[RACER X #99]

Scott,
No matter which brand you use you MUST bleed before every weekend of track time. Some guys will bleed their brakes every day of track time.
Cranky

BTW, If you have a hydraulic clutch, bleed that also. The engine heat gets to the clutch system too.

[coyled]

Jim, willwood just told me to replace the seals in the calipers and masters. If you just flush the system and have any dot 5 left, when it combines with dot 3 or 4 the seals can expand a lot. Cranky, its been 4 race days since I bled my brakes. I'm not going to short cut on this one; a flush, new seals and castrol, also bleed before every race weekend. I am always worried about running out of driver let alone brakes or tires. Thanks for the advice guys. scott

[BT SNAKE]

It seems that silicone brake fluid is taking a bad rap
here . Just where is a good applicable place for the
stuff? It hasn't been on the shelf for twenty years
because its pretty and saves your paint. I have the
stuff in my cobra and it has been in there for 11yrs
No problems. I also have a 34 Ford street rod I
built in 1984. I have it in that as well. Not one time
have I experienced a problem with it. I have little
track time on the cobra, but it has seen its share of
autocross. I also have it in the slave cylinder. As far
as I can tell it has gone beyond the call of duty. I
will continue to use it until something subsantial
comes along and says its really really Bad!!
Hence, no recalls as I know of as yet!
I do bleed the brakes when new pads are installed.
Properly maintained brakes will not acquire moisture.
Brake fluid does not absorb water. when water is present it will mix when agitated but it will then
seperate over time. It causes the same damage in
any other system thats suseptible to moisture.
The stuff has a 500 degree wet boiling point. Unless
you're running Sebring or Le Mans you shouldn't
need more than that. Water in any system boils at
212 degrees. Hygroscopic or not, water should not
get in the system period.If it is then you got a bigger
problem.
BT SNAKE
Hersh

PS. Scott, I think you may have to rap the header thats
under the master cylinder as thats what is causing
the extra heat and the spongy brakes. I believe
you will have the same problem with the Castrol SRF.

[coyled]

Bt snake, My brakes would get spongey very fast with your standard off the shelf brake fluid. That is after a 20 minute session at PIR. We then changed to this high temp silicone and it lasted longer, with more sessions before that spongeness. If it were header heat related, it would do it every session. If you road race at least in my car, it sees some severe braking and brakes very well when the pedal is not sponge. When I let Gordon Levy drive the car the spongeness gets worse as he drives it deeper than I do. Wilwood, RDI in N.C. and Borris Said told me that silicone is not good at all for road racing. But for auto crossing or street driving I would, like you be satisfied with silicone. scott

[BT SNAKE]

Scott all you did when you went to silicone was
raise the dry boil to 350 degrees, there for it took
a little longer for the heat to take effect. I experienced
the same problem of mushy brakes when I first
built the car. I had no protection around the
master cylinder from header heat. A good friend
of mine who happens to have been a crew chief
on a nascar team, looked at my problem and told
me to wrap the headers with two layers. I did and
I never experienced the problem again. Also I found this
on the russell brake fluid bottle.

DOT 5 Silicone Brake Fluid was developed for severe service and competition applications. Complies with Federal Motor Vehicle Safety Standard #116, and will not boil at temperatures up to 500° F. Russell Silicone Brake Fluid is not hygroscopic (it will not absorb moisture from the air) and will not damage paint or chrome. Not compatible with DOT 3 and DOT 4 brake fluids.
So go figure. Who's right? I say show me that it is
definetly the silicone and I will change. Until then
I'm sticking with it. In this climate I seriously
dought that moisture will be a problem.
Your Friend,
BT SNAKE
Hersh

[a427sc]

I agree that a good race brake fluid is required (I use wilwood550). But you should also check out better air flow to and out of each brake rotor/wheel.

I use the oblong air intakes either side of the rad opening, ducted directly to the center of the rotor in front. Extra air can be taken with a small scoop through the side wall inside the rad inlet and piped to the same place. Do the wheels you use have enough opening to pass the air flow out?

And in the rear, inboard or outboard brakes? Until I got a strong flow to the Jag inboards, 5-6 laps was all there was. I set up a snorkle, ducted to the rears, as my car has no windshield (the blackbox next to my head in the picture). When I had the windshield on, there are 2 high pressure areas to draw from. One is alongside (protruding forward about 1" ) the passinger side of the w/s. The other is on the cowl just behind the door, where the body curves up.

good luck

Don

[BT SNAKE]

Don, You are one smart cookie!
The biggest enemy to brake systems on race cars
is heat . By doing things like you did to your cobra
you improved the performance emminsly. I
would bet that you notice a radical difference in the
brake performance with the new ducting.
I.m surprised that someone hasn't made fiberglas
tunnels that would fit behind those small vents on the
front of the cobra. Aimed properly at the brakes they
would really do the trick for road racers.
Your Friend,
BT SNAKE
Hersh

[coyled]

Don, I originally had a medium compound pad but was not happy with the brakes when they were really hot on a road course. I then went to porterfields r4's, I think. When they are cold they do not work great, just o.k. But once they warm up(2 corners) they work really well. I have never been completely thrilled with the pedal and now the spongeness. I have not vented the pads, I have the original pin drive rims. I don't think I am cooking the pads at this point, just the fluid. Hersh, I see your point about the master and its closeness to header heat. I still think I am going to change the seals and go to willwood or castol nonsynthetic fluid. I just thought of something; at willow it was the first time on the goodyear bias ply slicks, they probably generate a lot more heat than the hoosiers, maybe some of it went thru to the calipers to help cook the fluid. Maybe this is overkill, but I had rather be as sure as I can be when dealing with the braking system. Thanks, Scott

[a427sc]

Cooking the pads will give you no braking effect (fade), but the pedal will stay up. Boiling the fluid will drop the pedal, but pumping will restore braking effect.

Routing air into and out of the rotor (via the internal vanes) helps disipate the heat that transfers from the rotor/pad interface into the caliper and boils the fluid.

New seals, wilwood 550 or the new 600 should suffice if you do some basic air ducting, and save a few bucks in the process. Not familiar with the Castrol high $ fluid, but am sure it brings it's own problems to the party, such as corrosivness to the system etc.

Of course, you could always just tighten the belts, dump some ice in your pants and go for it...

Don

[coyled]

Don, actually last night while pulling my tremec(won't down shift into second or first, noisy 5th gear), the master is close too the headers. The pedal sinks a little than pums up, so I think its fluid/air/boiling related, not pad fade. Maybe I'll heat shield the master or wrap the headers as suggested, then run venting to the rotors. Just getting in this thing takes some nerve, at least for me. scott

[RACER X #99]

Scott I agree with Don about venting the rotors. I have a flexible 3" hose that runs from the air cutout in front to
the center of the front rotors. I have no fade with front brakes. I also installed a Stainless steel deflector just above the headers and below the master cyl. this seems to help with the problem of cooking the brake fluid out of the master cyl. I have not had to do any venting of the rear brakes like Don has,but you and I don't have that heavy FE engine to slow lown.
Cranky,
BTW I would be interested in hearing what happend to your Tremec as I an running the same.

[BT SNAKE]

Scott,
I thing you are on the right track. Racer X brings in a
good point about the stainless deflector. Make sure
you put some header wrap on the bottom of that
deflector as well as wrap the headers. I gaurantee
you will notice the difference and the problem should
cease. The synthetic brake fluid should be OK. I
have no experience with it and I don't know anyone
that does.
The next best thing you can do is duct the brakes.
this really helps alot. Most every Hi performance
racer out there has a brake ducting system.
I hope this helps you out
Your Friend,
BT SNAKE
Hersh

[BT SNAKE]

Hey Scott,
How about an update on your brake situation.
Did you get it together and tested? What did you do
for the cooling aspect?

BT SNAKE