333pg333

Just want to get an impression of everyones brakes. What I'm looking for is what sort of pedal pressure you guys experience? Does your pedal go halfway down before you get solid retardation? I'm talking more on the track, but road is also good to know.
The reason that I ask is that I have always felt that I have a soft pedal and I've got all the right stuff on mine at the moment. Big Reds, s/s braideds, 3" ducting, Dot 5 fluid, PFC pads. The fluid has been changed and bled many times and I have a new stock master cylinder.
I find that I have to press the pedal once before my first hard application as if I'm filling up the brake booster. It just seems to firm up the pedal a little. Lindsey describe that they have only 1" pedal travel on their race car which I've not heard other people say they have? Sam Lin also said that once you even go up to BReds that you should change out to a larger master cylinder to keep up the pedal pressure and he's the only other person I've seen mention this apart from myself. Does anyone have any idea what other, larger m/c would fit our cars? I thought the 993tt could work but they are not a vacuum system. Does anyone know how large our stock m/c's are? Apparently a BMW 7 series from the 1990's works with our cars but I'm not sure how to find out which one.
Any ideas, clues, experience is appreciated.
T.I.A.

DanR

must say that I am running my stock turbo S brakes with some race pads from performance friction brakes and they are AMAZING. They are by far the sharpest brakes I have ever used. I got back into my 997 after a weekend track session and almost hit the wall at the end of our road as in comparrison they feel like jelly. pedal only needs a quarter travel and they bite hard!!!

Just wish I knew how to adjust my brake pedal height???

shiners780

Ding!

It's silicone based, allows more space between molecules for air to reside, making it more compressible (ie. spongy brake pedal feel) than the Glycol DOT 4 fluids.

333pg333

Ok that's the first time I've heard that. What brands would you suggest or use?
thx

goldminer

I'm running standard turbo S brakes and I have a "lot" of pedal travel before I get some pressure. It's certainly more travel than on my 930. My mechanic said that it is because of the different linkages required to convert our cars to RHD. That may explain why our cousins across the pond report firm pedals and ours are soft.

shiners780

Are you sure you are using DOT 5 and not DOT 5.1? There is a big difference.


Brake Fluid Dry Boiling Point Wet Boiling Point

AP SUPER 600 590°F 410°F
CASTROL SRF 590°F 518°F
NEO SUPER DOT 610 610°F 421°F
MOTUL RACING 600 593°F 420°F
MOTUL DOT 5.1 509°F 365°F
ATE SUPER BLUE 536°F 392°F
VALVOLINE SYNPOWER 503°F 343°F
ATE SL 500°F 329°F
CASTROL LMA 450°F 311°F
AP 551 528°F 288°F

Close your eyes and pick one. Ask 10 people for their favorite and you'll get 10 different answers. Ate is popular because it's cheap at $10/liter.

333pg333

Yes I've also considered that, but I have heard of guys in the US with softer pedals too. I really want to get a larger m/c in view of going up again in caliper size in the future anyway, however this is to learn what all you guys are experiencing and finding out new info like the DOT 4 stuff.
thx

333pg333

But these are DOT5's? Wouldn't you suggest using a DOT 4 on what you were saying? I use the Castrol SRF at the moment.

PorscheDoc

I've got a customer's F class turbo S that does the same thing. I have yet to figure it out. He runs the same pads, fluids, etc that the rest of us do (both S and non S), and no one else has the issue. Only thing I can think of is that a caliper pot is hanging up somewhere.

Geneqco

Didn't realise you were using Dot 5 Patrick... I thought you used Castrol SRF. I've also heard the Dot 5 (Silicon) issues.

Here's a quote that perhaps explains the issues with Dot 5 for racing applications:

We do not recommend using DOT 5 fluid in any racing applications. DOT 5 fluid is not hygroscopic, so as moisture enters the system, it is not absorbed by the fluid, and results in beads of moisture moving through the brake line, collecting in the calipers . It is not uncommon to have caliper temperatures exceed 200 F, and at 212 F, this collected moisture will boil causing vapor lock and system failure. Additionally, DOT 5 fluid is highly compressible due to aeration and foaming under normal braking conditions, providing a spongy brake feel. DOT 5 fluid is best suited for show car applications where its anti-corrosion and paint friendly characteristics are important.

Here's a link with further information:

http://www.gs610.com.au/html/quad/Si...ake_Fluid.html

You will also not that Dot 5 should not be used with ABS systems.

As for the linkages - there'd have to be a fair bit of play to be causing the problem.

Bri Bro

I have been using Valvoline Synpower Brake fluid for three years. I used several other brands but grew tired of the cost and lack of availability. I found that VALVOLINE is available at many Auto parts store making it easy to get a fresh bottle anytime or anyplace, and is under $7 a bottle. I always do a large brake bleed the night before running the car. I get very good brake pedal with little travel and good modulation.
So, what did they go and do, they discontinued the product last month. DOT 5 carries too many problems with it, I will be lloking at a DOT 4 that doesn't cost a arm and a leg.

Geneqco

Sorry, I see there's been a few posts while I was finding some links.

Castrol SRF uses a patented silicon ester technology but is quite different in its characteristics to Dot 5 from what I understand and is not really considered a Dot 5.

Here is another link:

http://www.titanmotorsports.com/casrfbrfl1li.html

xsboost90

have you ever adjusted the travel in your brake pedal? Mine is pretty stiff- only about 1" travel and when i get on the brakes hard they stop perfect-no pumping etc. I would try doing a vac test on your booster-or unplug the check valve and see if it holds pressure- could have a blown diaphram- or maybe the mc is bad somehow. I've dealt w/ mushy pedals before and then found out later that it was not "how it is" but rather something was up.

333pg333

Ok Scott, I thought that the SFR was a DOT5 but it seems as if it's not quite the same, so digressing to what Jim was saying would I be better off trying a DOT4?
Dan, yes you could be right. I did replace my m/c with a new one and nothing changed. As for my travel, I have a feeling that the pedal is adj. down as I actually had the brake pedal itself built thicker for better H&T'ing. So I would assume that in doing this I have reduced the travel to the lowest setting. I should follow up on the booster though you'd think that a leak would be pretty obvious. I can get decent retardation if I really squeeze the pedal down on the track, but I'd really like one of these mythical 1" travel models lol.

Geneqco

I would not expect the SRF has anything to do with your problem... it is rated as a DOT 4 but the minimum requirement for DOT 4 is much lower so I would not use just any DOT 4.

I have not personally used the SRF but have used MOTUL RBF 600 and Nulon Super DOT 4 both with good results. The MOTUL is around $25 per 500ml bottle locally and the Nulon is only $5 from TLC... it's only slightly below the MOTUL... from memory very similar to ATE Blue... maybe a little higher in boiling points.