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Jul 8, 2005 10:29:04 AM

xyz: Newbie; Loc:; Posts: 29, Gallery; Registered on: Dec 16, 2003

GT3 Brake Issue

I have had my first replacement of a standard set of GT3 brakes and -fluid at a London Porsche dealer. The result was awful. Having usually been out on track days for 25-30 mins (with the first set of discs and pads) with no fading at all, constant and good feeling brake pad (and this at 6 track days!) I have now had my third track day with the following result: chewing gum like pedal, early anti-lock effects, 8-10 mins of no fading on hot laps, followed by horrible brake fading with even taking straight exits instead of turning in into a corner. Even at travelling speed (I have been on vacation in Wales before that track and drove some 2000 kilometers) I had the feeling that the brake performance is somewhat disturbed. Would like to hear your opinions what the reasons could be. I am definitely going for other (probably Parr) pads soon, but anyway I do not think that standard Porsche brakes can be so bad after maybe 5000km and three track days.

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Jul 8, 2005 2:57:52 PM

W8MM: Rennteam Master; Loc: Cincinnati, OH , United States; Posts: 3995, Gallery; Registered on: Aug 8, 2003; Reply to: xyz

Re: GT3 Brake Issue

My barely-founded speculation is water absorption by the brake fluid. It's important to get ALL the old fluid out when changing brake fluid.

Most brake fluid is hygroscopic to some degree or other. When the caliper temperatures rise during heavy use, ANY moisture that has found its way into the brake fluid (however tiny) lowers the boiling point of the fluid. That's my favorite speculation as to the excessive fade you experience.

The chewing-gum pedal feel is probably caused by incorrect, or incomplete, purging of trapped air bubbles (or some other compressible ingredient) in the brake system when the fluid was changed - notoriously in the ABS valve body in some brake designs.

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Jul 11, 2005 9:16:00 PM

Ferdie: Rennteam VIP; Loc: Europe , Germany; Posts: 8234, Gallery; Registered on: Jul 2, 2004; Reply to: W8MM

Re: GT3 Brake Issue

That sounds pretty weird and albeit I wouldn't declare Mike's comments as erroneous I would be really surprised if this would be the case.

If it IS than it must have been caused by a peripherical problem, this should not be due to brake pad or rotor wear-out.

Did the brakes feel very hot after your track session? Unusually hot?

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Jul 13, 2005 5:37:00 PM

xyz: Newbie; Loc:; Posts: 29, Gallery; Registered on: Dec 16, 2003; Reply to: Ferdie

Re: GT3 Brake Issue

Ferdie and Mike, thanks a lot for your ideas. Brakes have been hot but I would not describe them as having being extraordinarily hot... it is weird indeed. I will try to fix an appointment with an expert here in London and will keep you updated.

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Jul 13, 2005 5:50:44 PM

fritz: Rennteam VIP; Loc: BaWü , Germany; Posts: 10248, Gallery; Registered on: Jul 23, 2003; Reply to: xyz

Re: GT3 Brake Issue

Came late to the party, but is there any chance that you had racing brake fluid in the circuit before the brake pad and fluid change, and do not since the fluid change?

If that is not the explanation, I'd check that the shop installed the right pads. They are color coded.

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Jul 14, 2005 12:52:15 PM

xyz: Newbie; Loc:; Posts: 29, Gallery; Registered on: Dec 16, 2003; Reply to: fritz

Re: GT3 Brake Issue

Fritz, the pad thing was an idea I have had as well... although I doubt that a Porsche dealer puts wrong pads to such a car. However, you never now...

As to my knowledge the old brake fluid was standard fluid, same as the new one. Camtune will pick up my car Monday morning to check.

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Jul 19, 2005 9:45:10 AM

xyz: Newbie; Loc:; Posts: 29, Gallery; Registered on: Dec 16, 2003; Reply to: xyz

Re: GT3 Brake Issue

Apparently it was more or less my fault - the guy from the garage told me the brakes and brake fluid went far too hot at certain point in time which killed the pads and the fluid. Strange anyway because I gave the car the same breaks during the trackdays as I did before. I will now have race pads and synthetic fluid fitted. I hope it is going to be much better as many people in the forum (in other topics) already indicated. Only concern is about noise...

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Jul 19, 2005 8:58:24 PM

fritz: Rennteam VIP; Loc: BaWü , Germany; Posts: 10248, Gallery; Registered on: Jul 23, 2003; Reply to: xyz

Re: GT3 Brake Issue

Quote:
xyz said:
Apparently it was more or less my fault - the guy from the garage told me the brakes and brake fluid went far too hot at certain point in time which killed the pads and the fluid. Strange anyway because I gave the car the same breaks during the trackdays as I did before. I will now have race pads and synthetic fluid fitted. I hope it is going to be much better as many people in the forum (in other topics) already indicated. Only concern is about noise...

Thanks for the feedback, xyz.

It's always good to hear about it when a problem is resolved, or at least fully diagnosed, because other people can benefit.

Sounds like the second set of brake pads was not sufficiently "tempered" before you went to the track for the first time.

Tempering involves curing "green" pads by hard - but not excessive - braking before they are more heavily (thermally) loaded for the first on the track.

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Jul 20, 2005 9:26:18 AM

xyz: Newbie; Loc:; Posts: 29, Gallery; Registered on: Dec 16, 2003; Reply to: fritz

Re: GT3 Brake Issue

Fritz, thanks for that tip - I was giving very weak instructions when I picked up the car the last time. They only said that I have to be "smooth" to the brakes for 100km. Could you please expand a bit on how you would ideally use new brakes for the first kilometers?

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Jul 21, 2005 8:57:33 AM

alexpez: Newbie; Loc: newport wales; Posts: 7, Gallery; Registered on: Jul 19, 2005; Reply to: xyz

Re: GT3 Brake Issue

Not sure its exactly what you guys are after, but check out this link about brakes, lots of stuff in there about correct initial use and pad and disc brake-in http://www.stoptech.com/whitepapers/warped_rotors_myth.htm

pez

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Jul 21, 2005 7:15:23 PM

fritz: Rennteam VIP; Loc: BaWü , Germany; Posts: 10248, Gallery; Registered on: Jul 23, 2003; Reply to: alexpez

Re: GT3 Brake Issue

Quote:
alexpez said:
Not sure its exactly what you guys are after, but check out this link about brakes, lots of stuff in there about correct initial use and pad and disc brake-in http://www.stoptech.com/whitepapers/warped_rotors_myth.htm
pez

Thanks for that excellent link!

Good stuff; worth adding to your favorites. I'm looking forward to browsing the rest of that site.
For German rennteamers: the relevant article has also been translated, so you do not necessarily have to plough thru it in English!

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Aug 10, 2005 12:38:46 AM

FixedWing: Veteran; Loc:; Posts: 870, Gallery; Registered on: May 25, 2002; Reply to: xyz

Re: GT3 Brake Issue

Quote:
xyz said:
Apparently it was more or less my fault - the guy from the garage told me the brakes and brake fluid went far too hot at certain point in time which killed the pads and the fluid. Strange anyway because I gave the car the same breaks during the trackdays as I did before. I will now have race pads and synthetic fluid fitted. I hope it is going to be much better as many people in the forum (in other topics) already indicated. Only concern is about noise...

My experience was that it took a lot longer to properly bed in the pads with the PCCB system and that during that process they could be quite scary on the track.

Stephen

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Aug 16, 2005 12:02:40 PM

xyz: Newbie; Loc:; Posts: 29, Gallery; Registered on: Dec 16, 2003; Reply to: FixedWing

Re: GT3 Brake Issue

I was told by the guys who fitted the pads that they do not really need a special treatment to induce them. I was only told to be careful with them during the first 50 miles - that's what I did. Afterwards, I started taking them a bit harder everytime I braked. The race pads do need much more time to warm up, but then - they are a LOT different to the standard pads. Much more initial deceleration, much cleaner braking point. I am going to be on the track on Saturday and will report. What kind of problems did you experience?

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Aug 25, 2005 2:15:09 AM

Krlo: Newbie; Loc: Arizona / French Riviera; Posts: 12, Gallery; Registered on: Aug 25, 2005; Reply to: xyz

Re: GT3 Brake Issue

Sometime non OEM pads used to works at a higher temperature ... who's normally a good point ... but not when driving with OEM brake line. Steel braided brake lines could be an easy solution ... with rubber hose, the fluid under pressure flexes the hose, cause loss in firmness and reaction. With the steel braided lines (with teflon ?

), the response is firmer.

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Aug 25, 2005 12:54:31 PM

964C2: Expert; Loc: Dallas, TX , United States; Posts: 1825, Gallery; Registered on: May 11, 2004; Reply to: xyz

Re: GT3 Brake Issue

A soft, mushy pedal is almost ALWAYS air in the system. Your dealer may have done a bad brake fluid flush. It is best to do it with the engine running....because of ABS and the booster system, air may not get fully purged if you bleed the brakes without running the engine.

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