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Old 09-20-2003, 10:44 AM
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How do you pevent brake fluid from boiling?

Looks like I boiled my brake fluid at the track the other day.

Related thread:
https://www.bimmerfest.com/forums/showthread.php?t=41020

I now notice that even at stop signs, I can push the brake pedal down farther than before. OK, maybe I boiled the fluid and I have to change it now. No big deal. But how can you PREVENT the fluid from boiling?

I put this fluid in there in June for a track day then. Kept it in there since, with maybe 2,000 street miles driven. Then did this track day earlier this week that boiled the fluid. It's the version of ATE Super Blue that is the amber color, which made it nice and easy to change because I had the blue version in there before. So I'm using high boiling fluid. It was fresh from the can (i.e., not wet). I'm using OEM brake pads and rotor. I've got BBS RK wheels, so they have an open structure for cooling.

Just curious as to how you folks prevent boiling your fluid each time you go to the track. Thanks.
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Old 09-20-2003, 11:41 AM
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Several ways

1) Learn how to brake better. Harder braking seems to transfer less heat to the calipers.

2) Use a higher boiling point fluid. There are higher ones than Super Blue/Type 200, but that should be good enough.

3) Add brake cooling ducts.

4) Add bigger brakes, larger rotors mean more mass to absorb heat instead of transferring it to the calipers.
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Old 09-20-2003, 06:01 PM
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Hi Terry,

Thanks for the tips. I think suggestion #1 seems to be the best idea for me. I noticed that I was not breaking as hard as I should early in the day. So I was much harder on them for the second half of the day.

I would imagine that most people here are tracking mostly stock cars. So I should be OK without needing extra brake ducting, bigger brakes, or higher boiling fluid than ATE super blue. Although maybe that's not the case.
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Old 09-20-2003, 07:48 PM
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Quote:
Originally Posted by JonW
Hi Terry,

Thanks for the tips. I think suggestion #1 seems to be the best idea for me. I noticed that I was not breaking as hard as I should early in the day. So I was much harder on them for the second half of the day.

I would imagine that most people here are tracking mostly stock cars. So I should be OK without needing extra brake ducting, bigger brakes, or higher boiling fluid than ATE super blue. Although maybe that's not the case.
I think the general wisdom is that one should change brake fluid before each track event...

And yeah, braking harder, later seems to help one hell of a lot. On my first day at the track, I seriously toasted my brakes, but on the second they had no issues. (Other than the fact that the pads just couldn't keep up with the grip levels of the Azeni.)
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Old 09-20-2003, 09:23 PM
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Quote:
Originally Posted by Nick325xiT 5spd
I think the general wisdom is that one should change brake fluid before each track event...

And yeah, braking harder, later seems to help one hell of a lot. On my first day at the track, I seriously toasted my brakes, but on the second they had no issues. (Other than the fact that the pads just couldn't keep up with the grip levels of the Azeni.)
I don't know about that...

You certainly don't want OLD fluid in there, but a few months (even some DEs) should not be an issue with the ATE stuff.
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Old 09-21-2003, 01:11 PM
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In addition to the advice given by the other posters, the stock pads are inadequate for track use and transmit a lot of heat into the calipers/fluid. I suggest some track pads for the front. Also, the thickness of the pads makes a major difference in the heat transferred to the caliper/fluid as well. I'd suggest having at least 60% of pad material remaining before starting a track day.
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Old 09-22-2003, 09:10 AM
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What I've learned to do when in the braking zone is apply more braking at the beginning of the braking zone then to taper off my braking. Some people do the opposite and it's harder on both your brakes and your driving.

If you initially give allot of braking power, say a good 70-95% of your braking capacity early on, you can gradually ease off the brakes by the time you are at your turn in point.

I find this helps keep my brake temps down because greater heat is created at speed and of course at speed there's more air circulating around the brakes to keep them cooler.

Using this braking 'philosophy' also helps get your braking done and over with and lets you concentrate solely on the turn. Having to deal with turn-in, and braking, etc. all at the same time can be allot to deal with. Plus, as an average, you're only braking for about 5% of the entire track.
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Old 09-22-2003, 05:28 PM
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Quote:
Originally Posted by StahlGrauM3
In addition to the advice given by the other posters, the stock pads are inadequate for track use and transmit a lot of heat into the calipers/fluid. I suggest some track pads for the front. Also, the thickness of the pads makes a major difference in the heat transferred to the caliper/fluid as well. I'd suggest having at least 60% of pad material remaining before starting a track day.
I had fresh front pads this time. In the past, I didn't cook the brakes. And I was using stock/OEM pads which seemed to work fine. But I also had instructors with me. This was my first time out without an instructor. (Basically an open track day) Half way through the day I realized I needed to use the brakes harder, for shorter periods. And I kept to that for the rest of the day. Maybe I cooked them earlier in the day.
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Old 09-22-2003, 05:30 PM
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Quote:
Originally Posted by sergiok
What I've learned to do when in the braking zone is apply more braking at the beginning of the braking zone then to taper off my braking. Some people do the opposite and it's harder on both your brakes and your driving.

If you initially give allot of braking power, say a good 70-95% of your braking capacity early on, you can gradually ease off the brakes by the time you are at your turn in point.

I find this helps keep my brake temps down because greater heat is created at speed and of course at speed there's more air circulating around the brakes to keep them cooler.

Using this braking 'philosophy' also helps get your braking done and over with and lets you concentrate solely on the turn. Having to deal with turn-in, and braking, etc. all at the same time can be allot to deal with. Plus, as an average, you're only braking for about 5% of the entire track.
Sounds like good advice. Makes sense.
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Old 09-22-2003, 07:04 PM
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Quote:
Originally Posted by JonW
I had fresh front pads this time. In the past, I didn't cook the brakes. And I was using stock/OEM pads which seemed to work fine. But I also had instructors with me. This was my first time out without an instructor. (Basically an open track day) Half way through the day I realized I needed to use the brakes harder, for shorter periods. And I kept to that for the rest of the day. Maybe I cooked them earlier in the day.
What you are describing is pad fade not fluid fade, which is not surprising since you are using the stock pads. As you get more experience, you start driving faster and using your brakes more intensely, which perhaps explains why you had no problems previously.
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Old 09-22-2003, 09:01 PM
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Quote:
Originally Posted by StahlGrauM3
What you are describing is pad fade not fluid fade, which is not surprising since you are using the stock pads. As you get more experience, you start driving faster and using your brakes more intensely, which perhaps explains why you had no problems previously.
I think he may be experiencing both.

Brake fade is when the brake pad material has exceeded its maximum operating temperature(MOT). Every pad has a MOT. When you exceed this temperature rating, you'll get brake fade. You hit the brakes and the car simply keeps going. Your braking capacity just isn't what it normally is. For this reason, most people that run frequently on a track use 'track pads' that have higher a MOT rating. I'm sure you can do a search and find lots of info on good pads for track use.

Boiled brake fluid is different from brake fade simply because with brake fade, after the pads and rotors have cooled down, your braking power gets 'restored'. If you've boiled the fluid you'll have small air bubbles inside the hydraulic lines of the braking system. These bubbles will compress when you hit the brake pedal, thus causing that mushy pedal feel. You definitely need to replace that fluid.

Again, most people that track their cars switch to high temp (600F) Ate Super Blue brake fluid or equivelant. Also, since this fluid is quite anhydrous it is highly recommended to change it once every year if not sooner.
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