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Discussion Starter #1
Here's what I've got now: '65 factory disks/10" x 2" rear drums, R4S porterfield pads and shoes, 3" ducting in front blowing on rotors ala R-Model pic's I've seen, Race tires mounted on 15 x 7 Magnum 500s, Motol high-temp fluid

Performance this year has been improved over last year's stock everything, no ducting set-up, but at the end of 20 minute session I had brake fluid puked out from Master cylinder. Brake performance started good, got a little soft towards end but not terrible (still had pedal about 1" from floor). Take off MC cover, and still show plenty of fluid.

Am I keeping the MC too full? I keep it about 1/4" down from the top, may be should be less?

I've read past posts regarding ducting to the rotor center. I'm not seeing enough room to fit the duct onto the spindle and blowing toward the rotor center - most of the air will bounce off the spindle?? Maybe I'm missing something?

Has anyone else been running Mag 500 wheels on track? I think cooling the rotor isn't as much of the problem as cooling the caliper - that big hunk of steel is a great heat sink. I'm thinking I maybe the small slots in the Mag500 are negating the cooling of the ductwork, because the hot air isn't escaping the wheel /caliper area?

Any thoughts/ideas will be greatly appreciated... Thanks
 

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Send a PM to Dinosawnj. Bob has a 66 fb that he uses in open track events. Bob is very knowlegable in this area. He should be able to help.
 

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Your fluids boiling due to brake heat. There are two high temperature fluids I'm aware of: DOT 5 and theres a special DOT 3 fluid made by ??? DOT 5 is silicone based and does not mix with other fluids. If you use it, your system has to be totally flushed of old fluid before use.

Note: Fluids other than silicone based are hygroscopic meaning they attract and combine with water. This encourages rust formation in the system and turns the fluid black. If water is in your system it decreases the boiling point rapidly so you lose braking efficiency and the pedal becomes spongy. My advice first is to totally drain your system and refill with fresh DOT 3 fluid. Be very careful not to get water anywhere near the master cylinder (dripping off the hood for example). Fill it as you have been doing, about 1/4" from the top. Close it immediately after filling and never open it again unless you have brake problems. Each exposure to the air brings some water. If this fails try DOT 5. This will mean a complete flush. Heres some more info. Since silicone fluids are non-hygroscopic, if water enters the system it will sink to the bottom and occupy your wheel calipers/cylinders. This is bad news because the water will boil easily and will also corrode the calipers/cylinders quickly. Well tended, DOT 5 is great but you need to bleed off a small amount of it about every six months to ensure no water accumulates. DOT 3 is easier to maintain but does collect and combine with water. It needs to be replaced if it becomes dark colored indicating contamination. Hope this helps.
 

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First, a caveat. I have not done this yet. Braking in simple physics terms is taking forward motion and turning it into heat. Your brakes generate this heat via friction. Generally speaking, the more mass that the rotor contains, the more heat it is able to absorbed and displace. Stock 10 inch rotors do not contain enough mass to absorbed and displace the amount of heat the your 2800 lbs car can generate at a track event. Please note that this is different than a one-time stop. If you are serious about track events then you should consider installing larger front rotors. You 15-inch wheels should easily hold 11 inch and may be even 12 inch. A cheaper solution is to make sure your stock sized rotors are fresh (have a lot of mass); the vents are clear and direct your venting towards the centre of the rotor. Something that I have thought about doing but have not done yet on my track car is to install a small pump to spray a water mist at the rotor during braking. I think I might have this problems with class rules if I do that though. Good luck and hope this helps.
 

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I've run that setup before. The only difference between my current setup is I now run rear discs (I have a set of 2 1/2 drums I will be installing someday in the future). I have not had this happen, but some of the 5.0 guys I know have. They flush and bleed the brakes between every session and spin the wheels frequently until the rotors cooldown (they have warpage problems, are you experiencing this).

I flush my complete brake system before every event. I use Castrol Lima GT Dot3/4. My dusting is to the center of the spindle pin without a dust shield. My rotors are slotted (not drill) and I use a steel American Racing wheel with plently of cooling holes.

I assue you where running at NHI. I haven't been their since they changed their name from Loudon. Fairly tight course with elevation changes. Tuff on a heavy cars brakes. Lastly, do people comment that you use the brakes too much.

Bob.
 
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On the race car we had the ducts pointing at the leading edge of the rotor so that the air would be directed through the cooling slots. This seemed to work best for us(dirt track modified). By the end of a 10 lap heat race we would still have rotors so hot they glowed red. We used at that time,large remote reservoir masters with Castrol GT LMA fluid with the fluid level aprrx 1/2 from the top, yes the fluid expanded but it never puked out. Today there are better fluids for racing apps.
The Motul 600 is one of the best but it absorbs moisture rapidly, this is no problem on a race car just flush the system often.
Silicone fluid NEVER should be used in a race car.!!!!!!!
Silicone fluid is for show cars that are not driven. If it were that good it would be used by a major manufactuer as standard fill. Its not
NO manufacturer uses it or recommends it.
Every major brake manufacturer states it should not be used in High Performance apps.
 

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On speed Vision, there are European events where there is a lot of steam coming out of the front brakes. They use a water misting system on the brakes to help dissipate the heat faster. Seems to work great for them.
 

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Discussion Starter #12
Thanks for your help. The Motul stuff is Dot3/4, and fresh this spring, I don't think that was the problem, though I will flush and replace before next track day next month.
 

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Discussion Starter #13
I'm trying to avoid replacement right now, but will probably go to The Cobra Automotive big-brakes set-up in the next year, So I can keep the 15" wheels/tires and stay legal for any future vintage -events. Rotors are new '65 stock ones, Ductwork may need some re-direction I guess

Thanks
 

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Discussion Starter #14
Hi Bob, was hoping you'd weigh in...

I hope a flush between sessions isn't needed- between doing corner-work and checking everything else, the day is already busy!

I was trying to get the duct to the center , but it looks like it'll just blow at the back of the spindle, not thru the rotor. are you kind of wedged in the space behind the spindle, pointing at the rotor center? That's the only way I could see, but it looked like the hose would get scrunched when the wheels turned...

NHIS is just that, uses the front straight of the NASCAR track and then a bunch of turns inside and outside the main track. Lots of fun. Haven't had either instructor that's been inthe car with me say I use them too much- Though I was getting chided for coasting too much at first...They both complained about too much brake effort, but they both drive late model cars regularly with them new-fangled "power brakes"... One of the benefits of driving a dinosaur racer I guess!

Are the AR wheels the AR767 ones? Jegs has them $ 35 each, probably worth swapping them for the Mag 500s.

Thanks
 

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Discussion Starter #16
I considered the R4 pads , but the car is driven 95% on the street, 5% on the track, I didn't want to have to drag the pedal for the first mile on the way to work, cruise nights, etc to get them to work. Maybe I should get them anyway and just put them in for track days...?

Thanks
 

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My ducting blows thru the back of the spindle. I think I have a picture somewhere I can send you. My track wheels are the AR767's for now (I'd like a set of mini lities someday). If your going to flush the brake fluids before every event, then swaping brake pads to a track compound would make sense and is pretty easy. I have dedicated track wheels/tires, so before and after every event, I'm only 2 small bolts away from swapping pads.

Check with the vintage sanctioning body you plan to race with before you go the the Cobra Auto big brakes. Some of them don't allow the setup because of the aftermarket aluminum hat and rotor setup.

How far is Watkins Glen for you. I'm planning on going to an event in late October there.

Good Luck,

Bob.
 
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