nsxtasy

A couple of months ago, the question was asked on this forum how fast brake fluid absorbs moisture. (I did a search but I can't seem to find the topic.) At the time, no one knew the answer for sure.

On Friday, on my way to Road America, I stopped at Acura of Brookfield (suburban Milwaukee) for some service. This particular dealer does a lot of track car prep, including some full-blown race cars as well as many folks doing HPDE events in street cars. (How many dealers do you know that stock Motul RBF 600 fluid, camber kits, and brake applications with two-piece rotors? ) They have the tool that measures the boiling point of brake fluid. I asked their service director how fast the boiling temperature of brake fluid drops over time. He said that, with normal street cars using DOT 3 or DOT 4 fluid, the boiling temperature typically drops around 20 degrees F in a year. With cars being tracked a lot and using high-temp brake fluid like Motul, the boiling temperature can drop as much as 100 degrees F in a year.

So that's the answer to the question...

descartesfool

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nsxtasy &raquo;</TD></TR><TR><TD CLASS="quote"> With cars being tracked a lot and using high-temp brake fluid like Motul, the boiling temperature can drop as much as 100 degrees F in a year.
</TD></TR></TABLE>

Good reason to use Castrol SRF!

nsxtasy

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by descartesfool &raquo;</TD></TR><TR><TD CLASS="quote">Good reason to use Castrol SRF!</TD></TR></TABLE>

Well, that still leaves the boiling point of Motul RBF 600 around 500 degrees F after a full year of heavy racing, which is still pretty high...

dvp

I believe it. I use Castrol. After bleeding my system two weeks before, my vacuum brake bleeding system was covered with beads of water. It is pretty moist up here and the vacuum system was exposed more than the fluid in the car but still, it was eye opening. And the vacuum system has it's own case.


Modified by dvp at 12:45 PM 5/2/2006

descartesfool

Motul is good, but Castrol is better!

DRY:590F -- WET:518F --- CASTROL SRF
DRY:593F -- WET:420F --- MOTUL RBF600

Lose 100F from 593 and you have 493, which is still not full wet spec of 420 F for the Motul. Even at full wet spec, Castrol SRF is 518F. I assume that is why many race teams use it. Brake fluid is a really minor cost on a per year basis. Last time I added up most items for an event cost for me a little out of town, it was over $600/day. Do 10 days like that and you have spent $6000. Buy 2 half litres of Motul for about $24 or one litre of Castrol for $64, and you are out $40, which is not much of a dent in $6000. Some days I feel cheap and I buy Motul, then other times I buy Castrol. Brake pads cost me a whole ton more than fluid per year. I went through 2 sets of XP10's in 3-4 days each. That is expensive.

nsxtasy

Hey, I'm not knocking Castrol SRF. It's good stuff. But it does cost more. If you're changing your brake fluid at least once every six months before going on the track, the boiling point of Motul probably isn't going to be much different from Castrol. Except maybe if you live in an unusually humid area.

I have yet to boil Motul, and I've been using it for the past 15 years or so...

Evan55

sure, you can spend a little more $$ on better brake fluid. There are a hundred things on a racecar that you can spend a little more $$ on. The question is why would you fix something that isnt broken. Unless you are boiling your fluid frequently and hate bleeding every few weekends, it still doesnt make any sense to pay $70 for brake fluid

descartesfool

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nsxtasy &raquo;</TD></TR><TR><TD CLASS="quote">Hey, I'm not knocking Castrol SRF. It's good stuff. But it does cost more. </TD></TR></TABLE>

And I am certainly not knocking Motul, since I use it and have said many times that Motul is the "Best Buy" track brake fluid for max performance vs. cost. Many people also compare cost per can of brake fluids but forget that some cans are 1/2 litre and some cans are 1 litre. Here is a link to pricing http://www.raceshopper.com/cas...shtml that shows SRF at $63/can or $31.50 per 1/2 litre. Same site has Motul at $15 per 1/2 litre. That shows SRF to be about twice the cost of Motul, not four times as one might think by not considering can size. So yes, it is expensive, just not that expensive. I think brake fluid is like insurance, you sometimes by more coverage than you need.

About the 100 F drop in boiling point, is that for fluid taken in the reservoir or from the caliper, and does it vary from where you sample it or is it all the same?

Here is a chart of boiling point reduction for DOT3 and DOT4 standards. Scale on botom axis is shifted over bit


http://www.raceshopper.com/brake_fluid_faq.shtml

nsxtasy

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by descartesfool &raquo;</TD></TR><TR><TD CLASS="quote">About the 100 F drop in boiling point, is that for fluid taken in the reservoir or from the caliper, and does it vary from where you sample it or is it all the same?</TD></TR></TABLE>

Don't know, sorry...

blulude92

someone told me dot 4 gets contaminated quicker than dot 3. is this true?

Paluce

From the chart above it seams that it the looses it's resistance to boiling quicker than DOT3 given the same amount of water absorption. But It's still better. Was he refering to water absorption as "contamination"?

Tyson

how about just flushing the system more than once a year...

Jaker

Though my car is not a track car (autocross 25-30 events per year and daily driver), I get 18 months (the time limit on the can, no braking degradation) out of a fill of SRF. I was never able to get that much time out of the other brands of brake fluid I used (even with regular bleeding. I don't EVER need to bleed the SRF). That in itself is worth the price of admission.

nsxtasy

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Jaker &raquo;</TD></TR><TR><TD CLASS="quote">Though my car is not a track car (autocross 25-30 events per year and daily driver), I get 18 months (the time limit on the can, no braking degradation) out of a fill of SRF. I was never able to get that much time out of the other brands of brake fluid I used (even with regular bleeding. I don't EVER need to bleed the SRF). That in itself is worth the price of admission.</TD></TR></TABLE>

I'd rather use Motul RBF 600 and change it more often. Motul is a lot less expensive than the SRF (the SRF costs almost three times as much!) and has an even higher dry boiling point (593 vs 590). I don't EVER need to bleed the Motul RBF 600, even with the 10-12 track events I'm driving each year after flushing the fluid at the start of the season. That in itself is worth the price of admission.

nscirocco

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nsxtasy &raquo;</TD></TR><TR><TD CLASS="quote">I don't EVER need to bleed the Motul RBF 600..</TD></TR></TABLE>

really? mine needs changing after a race
this might explain it though



ducting and larger calipers/rotors (heat sink factor) should help fluid life alot

as for moisture .. just change it often, use new sealed fluid bottles, keep everything clean, don't re-use "clean" fluid you just flushed through

-nigel.

nsxtasy

Just to provide another data point...

A year ago I got some Motul RBF 600 to flush my brakes (dry boiling point 593F). I had a half bottle left over, and I left it capped in my basement. I just tested it for this season's brake flush, and the boiling point had dropped to 535F.

Chris F

Odd. Interesting.

slammed_93_hatch

i redid by brake system in 2006, put all new ATE super blue fluid, and haven't touched it since then with the exception of adding fluid when it gets low, and then giving one or two squirts to each bleeder when i change pads.

No fading, no boiling fluid, no problems. Although my car comes off the track at 2220lbs and only has 130hp!!!

beanbag

Theres some wilwood check valve thingie that you put in your brake line system such that the brake fluid circulates every time you press the pedal. Won't this help prevent boiling?

http://www.wilwood.com/Product...x.asp

AW

How do you test it? I have two half opened bottles and it would be a shame to just dump it if it is fine to use...

Crazydave

I suppose you could go in your kitchen, grab your nastiest pot,

dump the fluid in, pop in a termometer, and put in on high... and watch.

But then you would have boiled the fluid.

Which leads me to this idea..

Correct if I am wrong...

1.) A brake systems is a closed system
2.) when moisture is introduced into the system (I am guess from the atmospheric introduction down when the parts are assembled, fluided is added etc), the boiling point of the fluid is lowered due to moisture
3.) Moisture cannot escape becuase of #1... being a closed system


What happens chemically when you boil your fluid?

If you have some clean fluid that is sitting around... can you 'distill' the moisture out of it by heating to slightly above 212 degrees, (which should boil out the water) and then have some good moisture free fluid?

nsxtasy

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Crazydave &raquo;</TD></TR><TR><TD CLASS="quote">I suppose you could go in your kitchen, grab your nastiest pot,

dump the fluid in, pop in a termometer, and put in on high... and watch.

But then you would have boiled the fluid.</TD></TR></TABLE>

That's basically how the tester works. It has a probe that you stick into the fluid, and it heats up. It measures the temperatures, so when it boils, that's the boiling point.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Crazydave &raquo;</TD></TR><TR><TD CLASS="quote">Correct if I am wrong...

1.) A brake systems is a closed system
2.) when moisture is introduced into the system (I am guess from the atmospheric introduction down when the parts are assembled, fluided is added etc), the boiling point of the fluid is lowered due to moisture
3.) Moisture cannot escape becuase of #1... being a closed system</TD></TR></TABLE>

It's not a totally closed system. It can (and does) absorb moisture.