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Exactly what teams are using it, on track?

CT03911

Spent yesterday at a highly regarded New England race supply shop and today at a Grand Am, World Challenge and NASCAR Nationwide race shop asking brake questions.
My caliper rebuild kit is arriving tomorrow and I was scanning past brake posts. This one got colorful as many do.
The race supply shop told me to only use the highest temp fluid you need. Going for the "best" fluid means a more hygroscopic fluid and therefor the highest temp fluids need replacement the most frequently.

This is the reverse of what is usually preached here.

I posted HERE a few days back soliciting brake temps from GT3 users. I got few responses and no temps at all.
Obviously, the temps fluctuate wildly but if this group was checking the actual caliper and rotor temps we would know exactly what fluid would work.
The Pro team I talked to does this as a matter of course.
Guys in this forum seem to prefer to just throw the best fluid out there at the problem and are in a sense blind to what the problem, or temp, actually is.
I include myself in this group.
I intend to be more informed this season and am going to use caliper temp strips and rotor temp paint during my rebuild to see what my max temps are.
What the experts tell me is this:
If you use a really high temp fluid it attracts water even more and so the best fluids need replacement the most.
This is counter to what most folks say here and what we all try to get away from- the continual fluid flushes/bleeds.
The advice I get is to therefore run only the highest temp fluid you need to counter what your caliper temps max out at. That, and still bleed frequently.
Regarding caliper re-builds, the team I visited today does the NASCAR brakes every 1-2 races, all seals, etc.
The Grand Am and World Challenge cars goes a full season on a caliper.
Us DE guys can go a long time between rebuilds, multiple seasons normally and probably get away with just dust seals only after two years +/-
I use Motul 600 as of last season and bleed every 3-4 days no matter what. I had great brakes all season and see no need to use a "better" and more expensive fluid that experts tell me I need to bleed just as often if not more.
Now, should my caliper temp strips actually tell me I am near 600f I will have to go to SRF or the Prospeed but will plan on just as many bleeds based on what I learned the past few days.
Dennis

LVDell

Dennis, the problem is that the big ones that everybody uses are Super Blue, Motul, and SRF. If you are on track you do NOT want a fluid that you will boil. If you brake with any sort of zeal, then Super Blue is toast which is why most use Motul or SRF. What's more important (if you have a good fluid) is that you are matching your brake pad with your braking temps. Run some caliper paint to tell you what temp your are generating and match accordingly. All the brake pad manufacturers highlight the optimal temp range for the pads.

Not sure you are quite understanding the logic about bleeding the fluid and using a higher end fluid. In reality though it's not the higher end fluids that need replacement the most unless you are strictly running them for the street. Then you are wasting your money. But if you run the super blue's of the world then you are bleeding so damn much that it actually costs you more and you are bleeding more.

I have run caliper paint to indicate my brake temps and run the appropriate fluid (SRF) and pads (PFC01 and 06). I bleed after EVERY event when I do my pad changes.

TrackDays247.com

I'm even worse, LV: I do a caliper bleed after each track day. I'm no Mr. Expert Driver, but I've done 115 track days and the damn car has 514HP, each track day includes at least 3 1/2 hours of track time for me. "Cheap insurance" plus I've seen firsthand what happens to a car when brake go bye bye...mucho sobering.
So I'm paranoid ;-)

LVDell

Nothing wrong with paranoid! I'd rather bleed too much and know I have pedal that risk it. I just know I have never had to bleed with SRF but with Super Blue once I started getting to speed I was boiling after one session.

CT03911

Actually Dell, I think you missed the point of my post. Until yesterday I was in the camp of "better fluid equals less bleeding" which is what you are saying.

What I wrote as a result of my visit with experts is very DIFFERENT and contrary to popular practice and doctrine here.

They all told me the higher the temp brake fluid, the more hygroscopic it is. Therefore, you actually need to bleed a higher temp fluid more often.

I agree, they are less likely to boil which obviously would require a full bleed but I was not discussing that or confused with that.

Pick a fluid that is good enough to not boil. To do that you need to know the caliper temps or you are guessing.

No one has written a response yet to what the max temp was they have actually recorded on a GT3 caliper and under what circumstances. That includes the few responses I got from drivers who say they use caliper temp strips. No data.

Just throwing out highly regarded race shop advice. The Grand Am team incidentally uses AP600 fluid. They have found they do not need a higher temp fluid on any race car they have. Of course, they all have better cooling than a street GT3 but obviously push the cars more too.

It sounds like if someone likes SRF or Prospeed fluid for the high temp or pedal feel and don't mind the price- go for it. If you are using it because you think you can go a season between bleeds that may not be true.

LVDell

Actually you missed my point. But regardless, it's no big deal. I know what temps I run and I know what fluid and pads I run are appropriate for my application based on hours and hours of testing.

And, just to make sure you understand, everybody is DIFFERENT so you really don't need other people's temps. Cooling, braking characteristics, etc, all come in to play.

My shop takes very good care of me, has never let me astray, and just happens to be well respected in the Grand-Am/ALMS/etc pits so I'm not worried about it.

ps. I don't think ANYBODY has ever bought SRF because they thought they didn't have to bleed but once a season.

CT03911

Dell my friend, I am missing your point a bit I'm afraid
Look, I'm not trying to argue with someone as knowlegable as you and many others on here. I hate threads where guys seem to go back and forth over their opinions behind the shield of a forum. Not my style.

Look, I was trying to make a few points that seemed different than what I have been hearing here and on track.

First, no one on this forum has said a word about brake temps they have actually recorded. I find that curious. Race teams know that data is important. Of course we would all have different temps even on the same day and same car. We are all different. I still am surprised that a bunch of guys haven't thrown out some of the max temps they see under certain situations.
I am pretty sure that is because we as a group don't really do that.

I was suggesting it might be a good thing to know. It only costs the few dollars for a temp strip on the caliper. I never did it but intend to going forward.
I mean, if a bunch of guys were seeing 600F on their calipers then we better all be running SRF.
If NO ONE here has seen north of say 550F on a caliper than we can't be boiling the fluid unless your brake lines lay up close to a rotor. We would be experiencing soft pedals from air or water in the fluid. In this example anyone running fluid higher than say Motul 600 would be in the overkill category. I have nothing against overkill either. I just want to know where I am on that temp line.

The second point is simply that higher temp fluids are more hygroscopic. That's it. The higher the temp on the bottle the more it attracts water. Therefore, a higher temp fluid would need to be bled more in an apples to apples scenario. I suppose the better performance of the fluid may mask the true decrease in it's boiling point as it attracts water but it will attract water more. I don't want to speculate in that direction anyways.

I agree, ATE has no place in a GT3.

In closing, I know many people who have actually said they run SRF because they can go a whole season without bleeding and tons of guys on here say it. That is a practice a race supply and Grand Am team from here were trying to discourage.

I hope this clarifies what I was saying for everyone.

LVDell

Not argument at all. Just a healthy debate to try and understand. With that said, I'm not sure it's relevant or even needed for guys to post brake temps. FYI...I take my temps with paint specialized to record the temps my rotors emit. That helps determine the proper pad for me. As far as fluid, overkill works for me if in fact I am using a fluid that is overkill. And for most of us here, overkill is the norm. Take a look at our oil changes, gearbox oil changes, fluid changes, etc, etc, etc.. They are some crazy OCD intervals!

I don't see how you can go a whole season without a bleed when you are changing pads. You should ALWAYS bleed your brakes when you change pads.

I'm beginning to think this thread is running the course, don't you?

CT03911

It pretty much has for me.

I'd still love to know what the max caliper temp is that any Rennlister running a GT3 has actually recorded.
I am interested in that. Not an IR gun after a run and in the pits. A real temp strip.
Anyone out there that actually has recorded caliper temps feel free to PM me.
I am far less concerned with rotor temps personally.

LVDell

I'd have to go back through my GT3 logs to see what my temps were. I have a feeling all that is on file with the race shop and not in my personal log books.

ace996

I'll jump in here a bit, but only as a friendly...

The above is true, with MOST fluids. It is not true with SRF.

The dry boiling point is great if you do a full flush before your trackdays. I find this quite expensive with Motul, as I'm going through several bottles. And the fluid comes out like apple cider or worse.

With SRF, it has the highest WET boiling point...518 degrees. No other fluid has such a high WET boiling point. I don't really car if it's more hydroscopic than cheaper fluid (Castrol says it's not due to it's formulation), because when it does absorb some moisture, it's still better than most other dry fluids.

My last two years tracking an E90M3 and a C5Z06 with SRF, I've actually spent less on brake fluid than when I used Motul600. This is because I only need to do a simple bleed of fluid, not a full flush, to rid my system of fluid that's absorbed too much moisture. I'd never go to a trackday without at least a caliper bleed beforehand, just to rid the calipers of any boiled air, but I'm done with the bottles of Motul in my garage. A shot-glass of fluid out of each caliper to clear the air and burnt (if any) fluid and I'm good to go.

And if you run fast, you're hitting some real temps on those calipers. Boil fluid once, have your pedal go to the floor at 100mph once, and that's all the proof you'll need to run the "highest" boiling point fluid you can find. The most important "highest", IMHO, is the WET temp. And it'll take some pretty damn good fluid to make me switch from SRF...


Here's a listing of fluids, dry boiling points and wet boiling points for your review:
Fluid Dry BP Wet BP Est. BP after 6 months
Castrol SRF 590 518 554
NEO Super DOT 585 421 503
Motul Racing 600 585 421 503
Motul DOT 5.1 509 365 437
ATE Type 200/ATE Super Blue 536 392 464
Valvoline High Perf Synpower 503 343 423
ATE SL 500 329 415
Castrol LMA 450 311 381
Gunk DOT 4 Brake Fluid 510 311 411
DOT 5 Spec 500 346 423
DOT 4 Spec 446 311 379
DOT 3 Spec 401 284 343

AudiOn19s

That actually makes alot of sense. I was using the GS610 in early '09.

I'll put the 683 back on my list as a possibility for this season. The M3 is still full weight (nearly 3700lbs with driver and fuel) and is VERY hard on brakes!

CT03911

When I read Ace's and Audi's post, to me, we are back to my original question in this thread and another- what are the temps your calipers hit?
Again gents, I am not arguing SRF is great stuff just as the OP's RS683 fluid undoubtably is too.
If your rotor temps never get over 550 or so and I doubt they do, than you are not boiling your fluid as it came out of the bottle, even if you run Motul 600 or AP 600 like the race teams I visited.
The two professional sources told me high temp fluid attracts water faster than low temp fluid. Ace, you recognize this but as SRF's wet is in the low 500's if you don't change it all season it can be boiled and that is why you may see some "air" or "burnt" fluid that happens to be in there. You cooked it. True, SRF with a little water in it is better than many others and may well stay high enough you don't experience fade. Doesn't mean there is no water in the fluid.

The point is this. Water in your brakes is bad for calipers. So, even if they made a fluid with a 700f wet temp and you could run it for a decade as it got wetter and wetter, it would not be good to do so.
That was my exact point in an earlier writing. The high wet tolerence of SRF may mask the fact it IS WET.

Again, I am just passing along the well intentioned advice of two pro sources. Don't ever let it get wet, which you do by a good bleed program.
Second, just run the highest temp your brake caliper require- which you only know if you have temp strips on them. This, because lower temp fluids don't attract the water as much.

I could never argue running SRF or the RS683 is a good idea, just bleed more often than every pad change (12 days?) which is once or twice a season for most. Who knows, when I get caliper temps this season I may decide SRF or RS683 is better too if I am actually running up closer to the 600f max DRY of Moutul 600, but I will continue to bleed my calipers every 2-4 days as I do now.

One last example if I may. Lets say you put the car away last winter with fresh SRF (or fresh any brand) in it as you should have. This spring after a long winters sit, that fluid needs to be refreshed, however thoroughly you decide to do that.

spare tire

Rotor temps are factual but petal feel is subjective. All the talk of wet vs dry and need to bleed. Just like oil going off to a lab for inspection maybe brake fluid should go off to a lab to look for water content. After all the first rule of fast driving is brake less.