Sean F

How important is wet boiling point? I get dry boiling point, but how often does wet boiling point come into play. I'm curious because so many of the top fluids have similar or identical dry boiling points but SRF has considerably better wet. Is that why people say SRF is so much better? Is wet the more important measure?

ATE blue 536F dry 396F wet
Motul 600 593F dry 423F wet
SRF 590F dry 518F wet

ltc

Dry boiling point exists only in the can..unopened.
Once it's in the car, wet boiling point is the governing specification

chrisp

ltc, although you are technically correct I would tweak that by saying the longer it sits in the car the more the boiling point gravitates towards the wet b.p.. If you change your fluid just before every event then you can pretty much go by the dry boiling point numbers.

The advantage to SRF (I've read...I'm not a user) is that you don't need to change as often, once a year perhaps, because the wet b.p. is so high. Reportedly, it's not a worry to leave it in the car for several months.

ltc

Agreed.

Another cited advantage of SRF is not needing to bleed between runs/between days.

FWIW, SRF is the only brake fluid I'll use. My son will be competing at the US Kart Grand Prix in December at VIR ( they are using the Full Course ) and I will probably put SRF in his kart just for this event.

ltc

FWIW, SRF and boiling points, have been discussed many times in this forum. A search will likely answer any question that you could possibly have.

kurt M

Not true from what I have observed and tested. I live in Amazon like super muggy Wash DC area and I have a true boil point tester. Over a long soggy summer I run my fluid for 6 months and the boil points drop very little in that time. By “little” I mean at the most 5 or 8 deg total of almost 600. Some fluids are less susceptible to moisture absorption and or react less to the moisture. None of the super DOT 4 fluids are prone to rapid drop off of boil points. Leave it in for 3 years and you will see a marked drop off.
It is not a worry to leave Super blue or gold in your car for that time frame ether. It too will be at or near the dry points by a small fraction. If your braking system is so close to limits that a 2 or 4% drop in boil point is enough to fry the fluid you need to rethink the brakes
Not doing a full flush and only bleeding the brakes without not removing the contents of the reservoir first is not a good idea. The moisture contamination is highest in the reservoir. When you remove a small amount from each caliper you are also moving the most contaminated fluid towards and into the hottest components. After testing the condition of fluid at each component I now only perform a full flush to improve the condition of the fluid in the calipers.

Storage of opened cans. I have a partially filled can of super blue stores outside in an unconditioned space. It is now well over 4 years old and I test it once a year. So far it has lost something like 8 deg in boil point if I recall. (don’t have my notes in front of me) Metal cans with the lid on are a surprisingly good storage container. I don’t recommend that you use 4 year old stuff.
The point to this is that there are a lot of quotes and absolutes that might be only slightly founded. Is it good to change your fluid? Yes, does not hurt at all when done right. Does it go bad in short order? For the most part no and not at the rates than many would lead you to believe. Based on my own small # of sample test set I would not go more than 6 months in a track car and one year in all cars with a super DOT and one year with SRF in track cars.

ltc

OK, so if your 4 yrs old Super Blue has only lost ~ 8 deg boiling point, then why would you not recommend using it?

chrisp

CYA maybe?

kurt M

CMA Because storage and care might vary from person and place. Guy leaves cap off and can under a tree and thinks that it is still OK after 3 years cuz kurt m said so. Extreme example yes but there are good reasons to replace fluid in addition to the moisture issue. Brake fluids have corrosion inhibitors that are consumed after time and stress just as they are in coolants. Brake fluid contamination from internal points is a factor as well but this often is well less a factor than moisture. Live in an arid climate and other buildups might be a factor before water is. As I said I have a tester and use testing and evaluation to signal when to replace the fluid. I also use it to tell what the condition of the replacement fluid is when using a previously open can. Baring using a true boil point tester you have to use rules of thumb or the rules of the group you are driving with. I think some of the rules of thumb have gone a bit overboard. Again nothing wrong with replacing the fluid before each event. My point is the time money and effort might be better spent working on another aspect of the car and systems. As a former tech chair I spent much time talking nOObs into changing the brake fluid. “My 9XX is only 2 years old, the fluid has to be good as I never had a problem on the street” Once some track time was done I never had to remind them.
I also think we spend too much time blaming fluid when we are using under sized or under cooled braking systems. Increasing cooling pays back over many aspects over only increasing the resistance of the fluid

ltc

Could you please explain what a super DOT4 fluid is? I have never seen that adjective used in front of DOT4 previously.

George A

Kurt,

I'm not refuting your testing but my experience, especially with ATE Blue, has been that it will boil way before SRF after one month of use. Let's take the cooling away from the analysis (yes, my car did not have adequate brake cooling way back when I was going through this). What I found was that if I did not bleed the Blue before every event, I would eventually boil the fluid that weekend. I never did boil a fresh flush of Blue but have boiled month old Blue several times. Mind you, I live in a place hotter than hell, Texas. Now with the same pads under the same conditions, this never happened when I switched to SRF (even after I didn't bleed/flush for a year). So, based on my simple test, that shows me that the ATE does lose its dry rating fairly fast.

Is there something I'm not accounting for? I know that having the right sized and cooled brakes go a long way toward not boiling the fluid but what do you recommend to those that want to keep their cars stock or within a class (can only do cooling)?

George

kurt M

I don't doubt anyones experence. As I said my testing is 99% only from my own experence and 1% a few other cars fluids when I had drawn some off from the calipers. I found that the fluid in the cailpers was for the most part the dryest in the system. My data is presented as a single point. I am suprised that there are not more boil point testers in use. Mine was not real expensive considering what it does.

There might be some other factor at play with your car than true boil point that I / we don't know about. Resistance fatuge or something. It could also be that the fluid is drawing in moisture faster than in my test samples too.

What would I recomend? Same as most anyone else would I guess add more cooling. cooling that works. Some of the hose and duct setups look fancy but I bet there is little air movment after it makes it into the small ducts and down the long corrigated and convoluted flex tubes. Knock a hose loose (not uncommon) and you just might have much less as the duct ends and blocker plates can block the air.
Don't get me wrong here. I am not saying that folks are doing things wrong. I am pointing out that it seems like many folks do lots of things without knowing just why. I have always felt it good form to question and test when it is your own butt on the line.

George A

Kurt, just curious but did you test the fluid in reservoir or in the container? I wonder if heat (in the caliper) makes the fluid more susceptible to moisture. I've eyed some of the testers you are talking about, even the strips, but since I no longer have any brake issues, I've always passed.

You are right, cooling does make a big difference. And yes, I do knock off the tubes once in a while.

George

kurt M

All of the above. I pull and test fluid from the top, the calipers and the cans when they have been opened. I have been testing all the fluid I use and some of other folks as I help then do a flush ( as a former tech chair I used to do a lot of flush demos).
The test is distructive so I pull samples. I can test samples for anyone if they feel the desire enough to send me a small sample of about 3 tablespoons.

What is nice about the SRF is the high dry and wet points and very slow uptake of moisture. The only down side I see is the cost.

ronbo56

Here's my data point: cooling makes a huge difference. Before I installed my duct kit I needed a full flush after every event. With the ducting, I get much less fade and I can flush every other event if I want to (I may stay on the every event schedule anyway, not sure).

I use Super Blue bc it seems like the best compromise between quality and cost.