mark kibort

Yep.... this is very true. But, you are closer into the curve, so there is less distance to travel. a lot of trade offs, with lots of variables and factors.
I know for me to do a single apex with my brake situation, doesnt work. so, your right, i basically am going to fast , im not going to make it for a single apex turn in point ,which is a turn with more angle in it, so, i turn in early as you say, which gets off the brakes earlier and puts more burden on the front tires when turning to slow you down. it works. ive raced man over the years that run both lines during a race depending on the situation. Ive tried both, and didnt see any radical difference. So, experiment. do them both. you need to be able to get though turns a number of ways with out issues.

again, with your set up, weight and speeds (and brake components) ATE is fiine if new, but higher boiling point fluids cant hurt, and certainly if you are having any issues now, that might fix it.

Hatzenbach

OK,

my approach to fixing things is always one thing at a time, otherwise if the issue is fixed and you changed more than one thing, you don't know what fixed it.
So step #1 is that I ordered the GT2 brake ducts.
My next track day in Laguna-Seca is 9/1 (followed by Thunderhill "large track" with PCA the weekend after), then I'll know (hopefully).
If the GT2 ducts won't fix it, then the brake fluid would be the next step.

85Gold

One thing at a time is fine BUT if it doesn't work then your weekend is screwed. Brake fluid upgrade and GT2 brake ducts is the way to go for a start and the $ are minimal compared to the down time. If it was a large $$$$$$ expenditure then I would have a different opinion.

Peter

User 52121

I've got a lot of racing experience (albeit mostly on 2 wheels, not 4) and will say that Super Blue has never impressed me. I'll also second the advice for ducting, especially for Laguna.

Pony up for a bottle of Castol SRF and you'll only have to flush/bleed the system once a season.

Do both before your next event.

Hatzenbach

Point taken, but I don't think I will be screwed:
On my last track day last Monday, I had a soft pedal only in the last lap of session #4 (and this is what started the whole thread), so it was basically "borderline".
I am certain that the GT2 ducts will make some improvement over the stock ducts, so I am optimistic that I will be OK.

jrgordonsenior

..

Why are you so resistant to changing your brake fluid? Changing out your existing ducts isn't going to do squat. Sell your remaining blue bottles to Mather since he thinks it great stuff and buy some real brake fluid.

Oh and I didn't say it was crap, I said it was ****. Similar plumbing, different aperture and pressure (unless you're 65)....

mark kibort

Its a racing type fluid. its not bad, but it can be a band aid just to change the fluid. He bumps up the hp, or gets more agressive and that 100F fluid temp advantage of SRF, goes away pretty quick, and he has the problem again.
i think he has fixed the problem as he bled the system and the problem went a way. As far as experience, i probably have more races at this track than most any one in the world, because SCCA races there more than any organization in the world, and this is over 15 years all on ATE. ive run heavier cars, faster on this track with much smaller brakes and the ATE fluid worked just fine.
Because he is running into issues, and fade issues in the turn 11 area and not into turn 2, I would say this is an general overheating issue, and the cooling ducts might be the best solution. But, as i said before, much of the issue with his car is going to be driving style. Harder and faster on the brakes will help.
changing pads to something better than an endurance pad, might do the trick also. he might be having to press too hard to get the stopping force needed and (which can generate more pad heat, and then boil fluid) a more general race/street pad might do it for him.

I think you are probably fine after that last bleed and it does sound boarder line, so it might just be a combination of a lot of things that wont be there next time. (high track temps, air to start with in the lines).

mark kibort

I was having my issues with brakes and went to the stoptech brand. It did help a little after a long weekend, for just a little bit of that soft pedal you feel, after a race and you go to the next session thinking, " i should have bled them" But, it didnt solve my issue, which was not a soft pedal, but fade. (other topic)
so, i agree with you , it is very easy to change the fluid and the wet boiling point is about 100 F higher with stoptech fluid, which is much better than ATE, but SRF is very expensive, and I dont think his problem is that bad from what he says, and watching his video.. I think with a few changes, the ATE would work just fine. it is a street car btw, and the symptoms is an overheating of the braking system. so, brake ducts cant hurt. (i dont know what the ducts currently look like on a 911, so they might be starved even for deflected air). and sure fluid change might solve it too.

mglobe

Why would you ever want your brake fluid to be "borderline"? The cost of SRF (or Motul, or Prospeed 683) is nominal compared to the potential consequences of having your brake pedal go to the floor at just the wrong moment. What you spend on the most expensive of brake fluids is a drop in the bucket compared to tires, brake pads, hotel rooms, fuel,... Crap I better stop now before I start adding it all up.

Hatzenbach

OK,

I guess the question here is
a) do I want to understand (with a methodical approach) what was the reason
- or -
b) do I simply want the problem to go away?

My current approach is a) but I see everyone's point why b) seems to be the faster approach.
I guess b) it is then...

last question before I order the Motul: somewhere in the back of my head I seem to remember that the Motul had some nasty side effect? My car's a street car (and actually my daily driver) after all.

John's 991

I use Castrol SRF with Pagid pads in my otherwise stock 991 with no problems and am sure Motul will be fine. In case you have not already found this information, here is a table of brake fluid temperature ratings.

Fluid Wet Dry Boiling Point
ATE Super Blue 396 536
Castrol SRF 518 608
Motul RBF 600 421 594


http://www.lelandwest.com/brake-flui...ison-chart.cfm

mark kibort

thanks for the mini -chart! (and by the way, "Wet" means basically when you crack the bottle open)
yep, the good stuff buys you about 100 degrees, but i if you look at this, motul, used by almost everyone, is only 25 deg better. wet boiling point is all you really care about. castol SRF is good stuff, no doubt, and the best part of it, is that it takes on less water, thats why it comands the 70bucks a bottle price vs 20 for ATE.
in the end, sure, you can buy all the best of everything and justify it by saying, what if i get a soft pedal and crash..... if that was the case, no one could ever afford to hit the track. best rule of thumb, have some common sence here. ATE has worked for years on race cars and street cars , and i dont think very many would say they have ever had an incident strictly based on the fluid.
you are well below the temps for the ATE. as you get more power and go even faster, and store up even more of that hotly talked about "KE". sure, upgrade to the better fluid. I use stoptech fluid. i think its about 50-80 degrees better than ATE,and for racing, its nice to have a fluid that never boils in my use, and that means less bleeding of the system that alone in labor savings is worth the extra cost.
So I think you have enough to go on now.
enjoy!

KaiB

My oil is green....

John's 991

Actually, I think wet boiling point is when the brake fluid has 3.7% of water by volume, which is a lot. While I am not a scientist or an engineer, I would suspect that brake fluid that is changed regularly and/or bled frequently would perform closer to the dry boiling point. Maybe figure half way between the two to be safe.

One of the main reasons I chose to go with the Castrol is the significantly higher wet boiling point (about 100 degrees higher than ATE or Motul). That would indicate to me that even if the fluid does get a couple percent of water in it, it will still perform on par with brand new ATE.

Yes, it is much more expensive - about $70 a bottle compared to $15 for ATE, but the total dollars involved are trivial compared to the gas budget for DE's, let alone tires, brake pads, rotors and T&E.

mark kibort

agreed..... probably a good idea to change it to something better. glad i did this season. first time in 14 years, racing on something other than ATE!