brake fluid

[coyled]

I was running motil brake fluid. I am flushing it today and putting in the castrol srf. I am going to heat shield the masters(2 masters) and vent the front brakes. I can run the venting from the area in front of the radiator(allready a fresh air vent there on both sides to draw air from) or from the oblong ducts at the front of the cobra. Does it matter which way I go and where do you vent the air to? does it matter? the easiest way looks to be on the front top aimed at the inside of the rotor/vents. Any advice? scott

[a427sc]

Coyled,

I would use the intakes infront of the radiator, since they are already there. Maybe even make a small scoop. Check out the picture of Jim Holdens FIA radiator inlet on the ERA site. 3" hose tied to the upper A-arm, as far inside as you can to avoid tire contact. On my ERA, I used the swaybar link with 2 flat washers and a locknut thru the hose, pinching the wire reinforcement. Simple and light. Get the hose as close to the center of the rotor as you can, and be careful if you use plastic dryer venting, it will melt(!) if too close. If you want to get fancy, you can fab up some aluminum nozzles to direct the air the last 3-4". The hot air will vent itself out thru the wheel and put brakedust all over your pretty knock-offs.

[BT SNAKE]

Scott , I hope this ain't too late . I found these on the ERA site and they look like what you need to cool those rotors.

BT SNAKE

[coyled]

BT snake, thanks for the picture. I may go from in front of the radiator as there are allready holes there plus I have the 3 1/2 inch tubes. Any good pictures of the tube to the rotor area? I am still a bit unsure, not a lot of room on mine as far as a big area to aim the air into the rotor. scott

[MIKE KENNEY]

Scott,

If you want I can loan you some rotor paint it will tell you what temp. you are running and then you can judge what to do. Also water is the big killer even here in the AZ summer we find it in the cup cars. As for bleeding at the track we do it every mourning. Ducts are a must for road racing and I have a set coming from California we can pull molds from. If they don't make it in time we can make some in aluminum like the first comp cars.



Mike

[coyled]

Mike, I am glad to see that you are posting. I think I have the duct problem solved. I may be interested in the brake paint at road america to see where I'm at. I have changed to the castrol SRF fluid. scott

[Excaliber]

I changed and flushed all the silicone out and went with Wilwood 570. My main problem was header heat boiling the MASTER CYLINDER fluid. So why did I switch? Because water WILL eventually get in your brake system, it's only a matter of time. Bleeding EVERY race, etc. etc. will help.

IF water IS in the system (and humidity is very high in Hawaii) and that water is NOT absorbed by the silicone fluid the water will boil and cause an air gap in the lines, calipers or master cyl. when it does. This could lead to catastrophic and sudden brake failure. The water actually wouldn't "boil" I think it would "flash" (from liquid directly to steam).

Not taking any chances. I believe Wilwood has a valid point about NOT using silicone. Willing to risk paint damage over fractures (car body and MY body).

Ernie

[BT SNAKE]

Originally posted by 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.

No kidding ! I still use silicone in all my cars and not once have I had any problems. I even have it in my GT40.

I'm sticking to my original statement.

hersh

PS...
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.

[Andy Dunn]

Brake Systems: Oem & Racing Brake Technology
by Mike Mavrig1An, Mike Mavrigian, Larry W. Carley



Page 180
"We need to talk about DOT 5 silicone fluid to resolve some questions. DON'T USE IT FOR RACING. The only advantages of silicone fluid is the fact that it won't harm a painted surface, and that the fluid itself is non hydroscopic. That is why it is popular with restoration, show car and street rod folks. However, in terms of performance, this stuff can cause real problems. Silicone fluid can become very unstable at temperature, resulting in a low or ever changing pedal feel. On the race track, this is obviously not a good thing.

Engineer to Win: The Essential Guide to Racing Car MaterialsTechnology or How to Build Winners Which Don't Break
by Carroll Smith



Page 189
"the silicone brake fluids have made progress since PREPARE TO WIN. Some of them are now almost useable in racing cars - but not quite. They still have high frequency vibration frothing problems and they are still compressible at high temperatures, which it is why it takes a few laps for the pedal to get spongy when gullible people try to use silicones to race with. We replace all out brake fluid long before it has a chance to collect moisture so I have never understood why anyone would spend money for the silicone ones anyway."

[Mike Braddock]

Scott,

What was the verdict on your brake updates? I just happened across this thread when Andy posted those two links and I wanted to add to all the good advice here that it's important to duct the air equally to both sides of the rotor to prevent warping them under severe braking. So the brake duct must be aimed directly at the front of the rotor, not to the inside swept surface only...

Mike

[bmalone]

Scott, I boiled my fluid at SAAC-27. Not a pretty picture--first had severe brake drag, then no pedal, then a fireball (fluid surged out of MC onto header).

Came to the conclusion that this was due to under-hood ambient temperature being too high. My MC is wedged under the fender well where heat would be trapped and one of my lines runs perilously close to a header.

Changed out to a superior fluid and the problem ceased.

[a427sc]

Mike

You are correct that both sides of the rotor should receive cooling air equally. But unless you are using solid rotors, you NEED to duct the air to the CENTER. Assuming the rotor was assembled on the correct side, the vanes act as a directional fan, moving air thru the rotor and out the outer edge. Equal cooling is the reason rotors are vented. Don't forget that the hot air has to have a place to go also, the reason wheels have vent holes. Air flow past the wheel and wheel rotation create a low pressure area in the center, pulling air (and brake dust) out.

Don

[Mike Braddock]

Don,

You are absolutely correct about ducting the air to the middle of the rotors and that the rotors pump the air radially outwards. My choice of the word 'front' was very poor and after rereading my last post, I was even giving myself the look . So we are now in agreement, the air must be ducted directly to the middle of a vented rotor. And as you also pointed out, the ducts would be aimed at the FRONT of the rotors ( ) for a car that uses solid rotors. I'm going to quit here while I'm ahead . Have a great evening!

Mike

[RACER X #99]

Got to agree with McFez on the brake ducting, goes to the center of the disc. And I will agree on this also when it comes to brakes, bigger is definately better.

Have a safe trip Don,
RD

[James Neal]

Some of you folks seem to be pretty well versed on the subject of brake fluid,my knowledge iss from hard knocks. I owned and crewchiefed a Top Alcohol Dragster in the late 80's and early 90's mostly U.D.R.A. and a few N.H.R.A. events. The car ran steady 6.20's and ran as fast as a 5.95 in 91' qualifying for the U.S. Nationals,We occasionally had inconsistent braking problems pressure changes and in turn some interesting problems. We were told by one of the leading brake manufacturers that silicone was the only way to go. But from the moment we started using it we experienced pressure problems.These brakes were frequently bled and maintained,we carried rebuild kits for the master as well as replacement masters and calipers. Dragsters dont have any flex lines in them solid all the way to the rear so no line expansion. Handbrake required three pumps to ready for stop just to be sure there was pressure there. Several racers during this time were experiecing these problems, Our solution given to us by a very wise fuel tuner. Get the silicone out and go back to old faithfull end of our problems! I really don't think this applies much to the street crowd but I believe competitive events you have to go with what works. Silicone has its merits , I'll let everybody else mess with it .See ya at the track, I'll be the guy with the leg that isn't shakin' from the lack a brakin. WHAT! THESE THINGS DON'T HAVE CHUTES.

[Richard Hudgins]

Hi Folks,

I will have say that I have never had any luck with silicone brake fluid.

The problems were mostly that we could never get the air out of the systems, therefore a good pedal could not be achieved. Also, had big temp problems with pressure spikes and seal failures, etc.

It would be nice if this stuff really worked as it is not hydroscopic. But that in itself does not offset the problems.

[Tommy]

What do you pros think about ATE Super Blue brake fluid (536 dry / 392 wet boiling points) for about $10/ quart?

[niles]

Coyled:
Lot of good dicussion. Don't think you've have got to the root cause of going spongy on the track.
It is caused by one of two things; your changing a drop of water to gas at about 212 deg or your exceeding the boiling point of the fluid somewhere(400-500 deg).

First: BTSnake is right you can have NO!!! water is the system. This is the most common cause. Everyone has experinced a soft pedal and upon bleeding found "one" 1/8 in bubble, bleeding that out fixes the pedal. One drop of water, when flashed to steam, becomes and stays a bubble abut 1/2 in long totally destroying the brakes.

1. The MC should be shrouded from the header with a heat shield, this stops the radiate energy from getting too and heating up the MC; low problablity. MC is big and has a lots of mass and it's 8- 12 in from headers.

2. Overheating the front calibre, exceeding the 500 deg and boiling the fluid in the piston. This is common when you really use brakes hard with race tires. Solution- ducts; everyone was concentrating on rotor cooling, who cares! rotors go to 1500 deg and glow but cool rapidly when brakes are released. The key is that you cant have the caliber get over the boiling point of the fluid inside; thats the priority of the cooling duct; most race cars duct to both. But, the spongy system is caused by the caliber overheating and flashing a bubble inside the caliber.

3. The most likely, your rear line probably turns up from your floor pan and passed within 1-2 in of a header pipe. On the track the radiate energy from the pipe is 10-20 times that of street driving. The most likey is that you are exceeding 400 degs locally in that region and flashing a bubble in the brake line.
My solution: run the line in a mesh/alum/silicon tube designed for that purpose, attach the line right agaisnt the glass foot box, then put a standoff heat shield between the line and header. My heat shield is stood off by a thick nut that attaches the heat shield. Leave the shield open at the top and bottom so the hot air can raise and cool the area behind the shield

gn

[BT SNAKE]

Here are some FAQ's about silicone. It fits my needs well however, if you are in competitive motorsport then I do believe the "racing type fluids" are the way to go.

Question
What is so special about DoT5 Silicone Brake Fluid? What does the DoT reference signify? Will it catch fire? Will it damage paintwork? At what point will it boil? How long can I keep it?

Answer
Brake Fluids and the rubber components in braking systems will usually be "DoT" rated. This is an abbreviation for the US Dept. of Transportation who have in fact defined the standards most producers adhere to. Most brake fluids are DoT3, DoT4 & 5.1 Polyglcol fluids ('glycol for short) though some Citroens use Mineral fluid. Our Silicone Brake Fluid is DoT5 and unlike 'glycols, it never needs replacing because it repels moisture. Because it repels moisture it lasts indefinitely - reduces corrosion and ensures the boiling point remains 'high' at 260c (500f) Unlike 'glycol fluid, Silicone will not damage paint. It will not catch fire easily and it's non toxic with no known harmful affects.

Question
Will it improve the performance of my brakes? Will I feel a spongy pedal?

Answer
No, except insofar as the benefits described above. If in fact you do feel a spongy pedal or in fact any other peculiar effects then it would suggest the bleeding process has not been carried out properly, or some other problem exits. AP Lockheed and Girling list many reasons for "spongy pedals" and none of them relate to the use of Silicone Brake Fluid.

Question
Who uses it as original equipment?

Answer
Nobody that we know of except Harley-Davidson in their bikes. It is more expensive than normal fluids and probably because of this no Vehicle Manufacturer seems ready to use it. The US Army use it exclusively in all their lighter vehicles as does the US Post Office. Silicone Fluid has a viscosity which is virtually stable, which in practice means it performs well through most temperature extremes - and that can make a lot of difference in very hot or very cold climates.

Question
Does it mix with other Dot rated fluids? Is it compatible with grease used in the system?

Answer
Silicone DoT5 Fluid will work safely in a system with other DoT rated 'glycol fluids should they become mixed, in fact it is compatible with all other DoT rated products. But be warned - if other non-rated products such as petrol, oil or greases are in contact with the fluid - who knows? The message is clear. Avoid using not approved i.e.. non-DoT rated products.

Question
Will water collect in pockets in the system? How do I bleed the system?

Answer
Water can only collect in the system if it has not been 'bled' properly. Do the job again following the Vehicle Maker's instructions.

Question
Do I need to rebuild my braking system before I use SBF? Do I have to change the Hoses or seals? How do I flush the system? Can I reuse fluid that has been through the system?

Answer
No you do not have to rebuild your brakes before using Silicone Brake Fluid - We never have - and we have had two vehicles go to 250,000 miles on it without needing a replacement cylinder or calliper. Of course it makes sense to ensure your hoses and other components are in good order - change them if you are in doubt - but best of all get the Silicone in early in the life of the vehicle. Do not be tempted to use any 'flushing agent' None that we know of are DoT rated (item above) and DO NOT be tempted to reuse fluid which has already been through a system no matter how clean it may seem.

Question
Can I use it in an ABS System?

Answer
We have used Silicone in a BMW 728i and a Rover 820si for more than three years. Both vehicles are equipped with ABS and both have now done around 100,000 miles without any problems and without the need for the 'expensive' regular fluid changes. Some dealers charge as much as £100 for this work

Question
Can I use it for racing?

Answer
Silicone Brake Fluid is not a racing fluid and we certainly would discourage it's use for serious racing service. However some owners use it for amateur club events in vehicles they drive to the track and for rallying and they report good results. There are special 'racing fluids' optimised for that application - but they are not Silicone.

Question
Why is it purple or why has mine gone Green/Yellow?

Answer
Silicone DoT5 is dyed Purple and that is part of the DoT rating requirements to differentiate it from other fluids. Sometimes after exposure to air, the purple dye might bleach out and the fluid will look green or yellow. This change is purely cosmetic and it in no way affects the performance of the fluid.


Question
How much will I need to fill the system?

Answer
A litre will be sufficient for most vehicle brake and clutch systems.


I hope this helps resolve some of the mysteries about silicone.


Hersh

[M. Farcus]

a427sc (aka Cheeks) is correct with the ducting and fluid recomendations.....anything that will stop that boat anchor he drives will work on anything.

Road racing an itsy bitsy 289 I use PFC Z rated stuff...fairly cheap and PF pads which are very easy on the rotors.

When I had a boat anchor like he drives I had to use AP-600 and still boiled fluid near the end of a 20 minute vintage race, even using cooling ducts to the center of the rotor.

The FIA cars don't require as much brake......and have outboard vented rears which help with the cooling.

Make sure you are braking correctly....have plenty of air ducted to the center of the rotor....if the fluid still boils (petal goes to floor)....try a small "Y" with a branch hose going to the caliper..this helped when I rowed my old boat anchor.

Cheeks mentioned Morty's FIA car with the ducting....did he mention that the ducts face to the rear?.......catches more air when backing the car out of the trailer.......that Morty, he's one smart son of a gun......

MF