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Discussion Starter #1
Bought a '09 CS in '12 and have been to the track on stock pads/rotors and it held up pretty well. People here were saying once the pads get down to sub 40% remaining, change them out. I swapped the pads for stock ones, but put the sport version up front (Cayman R). Initial bite on these around town isn't as good and a bit of sqeak/squeel, though on the track they seemed fine. After the last session I was getting a pretty discernible pulse at the pedal, which is continuing. Still have the stock rotors and no cracking between any of the holes. There isn't much of a "lip" where the pads ride, so normally I wouldn't think to replace the rotors. Without putting a run-out dial gauge on it, what do people think is happening? I've heard I might just need to clean the rotors as the sport material likes a fresh surface and I may have contaminated them?

On my first few track days, the car felt like it had awesome brakes, but either I'm getting better and running out of brake performance, or something is amiss. I've added the GT3 front brake ducts and I guess there is something similar available for the rear but requires more work than just snapping them onto some lower control arms? Dealer flushed brake fluid last summer.

New rotor and pad time?

Thoughts? Opinions? Bueller?
 

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I had a similar experience with my 07.. when I swapped from OEM to Pagid "Orange" pads. Seems that the Orange pads left something on the rotors that grabbed/pulsed when the OEMs went on and vice versa.. I made sure that I "cleaned" the rotors with brake cleaning solvent and a scotch-brite pad... That seemed to keep this in check. Wrapped disc's would also explain the pulsing.

D
 

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About the squeal: my new car--OEM brakes--squealed for a long time, maybe six months. Read it was normal here. Hard stops would fix it for a while.
 

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I had similar issues when I changed from OEM to track pads on my Audi a few years ago - after a couple of sessions at the track I got the dreaded "brake judder," which is the pulsing sensation you describe. It's due to uneven deposits of brake pad material on the rotors, either because the pads weren't properly bedded to the rotors when you swapped then out, or incompatibility of brake pad material between the old and new. You may be able to fix the problem by scrubbing the rotors, though I never had any luck with that approach. If it doesn't fix the problem then you'll just have to get a new set of rotors, and this time be sure to properly bed the brakes. On my CS I switch between Hawk HPS pads for street duty and Pagid Yellows for track and have had no problems at all with brake judder.

BTW, although people often used the term "warped" rotors it's very rare for rotors to actually warp.

One other suggestion: you should consider using brake fluid that can withstand the higher temps encountered on the track than the standard fluid that the dealership uses, and you should bleed the brakes before each track event. Motul RBF-600 or RBF-660 work quite well, with dry boiling points significantly higher than OEM fluid. The downside is that you must flush the brakes about every 6 months (certainly no less than once/year) because it is more hygroscopic than standard brake fluid, meaning it absorbs water out of the air and then its boiling point gets lowered dramatically. The wet boiling point of these fluids is actually lower than the wet boiling point of standard brake fluids. But it's worth it for the improved performance at the track.
 

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Excellent white paper. Don't agree with not topping up the reservoir but that's another story.

Bofus, I'd suggest that you use the same type of pad on all 4 corners assuming that I read your post correctly. CR pads in front and standard pads in the rear. If the friction characteristics are different enough you can upset the brake balance. Pretty sure the practice isn't recommended for this reason.

I believe that Porsche uses the ABS system to do the automatic brake differential (Don't remember the acronym but I suspect it starts with P) to bias the front/rear brake balance to accommodate changes in this from the way the car is loaded, new vs used tires front to rear etc. though I suppose they could have used a variable pressure regulator also. If this is the case the pulsing you feel might maybe be the system in operation.

Try matching pads and see if it goes away.
 

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Discussion Starter #8
Update-a-go-go:

Decided to do something about it. Ordered some Sebro slotted rotors, GT3 master cylinder, cayman R pads, Torque fluid, and ECS stainless lines. I had all the stuff ready to go and took the day off to do it; alas, I'm not finished due to mail-order issues.

1) Ordered a rear "set" of rotors. The box says "set" on them, but there is only a left rear. Mail-order joint not open until Monday. Drat.
2) ECS stainless lines in the rear are advertised as being exactly the same length as stock, but they are a smidge shorter.

Here's an install shot of the rear with the suspension unloaded:



Here's a shot showing the length difference (new on the left, stock on the right)



So, couldn't finish what I started or I'd be out trying out the new pedal feel. Had to make a run to the store to buy a T55 socket for the calipers and a 7/16" flare wrench. Nobody had an 11mm and the 7/16" one fit pretty well. Weird that they aren't all just 10mm. Master cylinder install was cake, but of course I haven't bled the system yet due to not being able to assemble the right rear corner. Not sure what to do about the brake lines in the rear. Seems like too much tension that could lead to premature failure.
 

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More than likely you have pad DEPOSITS on your rotors...do yourself a huge favor and get a set of proper track pads - either Pagid or PFC.
Of course we have BOTH, in stock.
 

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Discussion Starter #10
I had pulled the rotors and cleaned them with some sand paper and the pads too, I still had a pretty bad brake shimmy. I think a rotor was warped. The last time at the track, I would have to pump the brakes once or I'd have a lot of pedal travel. Reading up on this phenomenon, I was apparently experiencing pad knockback: a warped rotor pushes the pads away from the pistons and then you have excess travel upon first application.

Ok, so here's the last update.

I got the GT3 (cheap version) master cylinder installed and ECS sent new rear SS lines that happened to be a SKOSH longer. They still seem a little tight to me, but they assured me they were normal. I am using stock pads at the moment, but will be running pagid yellows for any track day. The 987.2 is so easy to change pads that running around town with noisy pads isn't necessary. I ordered all new pad sensors too so I can just pull the stock pads/harness out, then plug in the dummy ones for track use so I won't throw any warning lights. Got the system bled this morning and went out for a test drive. I would certainly recommend the GT3 master cylinder. The pedal is way up high and is rock hard. Modulation is still easy (no on/off pedal) and just gives a higher overall sense of confidence in your brakes.

A note about those that might take on the GT3 master cylinder install. There are lots of posts out there on how to bleed the system once you have the whole system open. Here's what I did and I can't imagine the pedal being any more firm. Here's my bleed procedure that worked and can be done 100% solo, though I do have the Motive Speed Bleeder and Durametric. Clutch seems unchanged, so I didn't bleed that system.

1) Fill up your reservoir
2) Attach the Motive speed bleeder
3) Pump it up to 23-24 psi
4) Go to right rear caliper
5) Loosen INSIDE nipple so that fluid is just starting to come out slowly with a clear tube into a clear jar/bottle
6) Go inside the car and press the brake pedal slowly to the floor
7) Engage the right rear durametric ABS bleed (I have the pro version)
8) Continue to slowly pump the brake pedal until bubbles stop
9) I used a spare iphone/ipad pointed at the clear caliper hose so I could "Facetime" and watch for bubbles whilst inside the car
10) Once done, exit the car and close the nipple
11) Do the same for the outside nipple
12) Re-do the inside nipple, just one or two pedal presses should be enough

Stop if the "low brake fluid warning"" comes on. Top up the fluid and keep going around the car: rr, lr, lf, then lr. The use of Facetime means you can watch the fluid for bubbles and you'll know when to stop. Just bleeding with Motive and NOT operating the brake pedal won't expel all the air from the master cylinder. Bench bleeding MIGHT help, but you'll have to pull the lines to connect to the car, only allowing air in anyhow, so skip the bench.

I went through just under 2.0 liters of brake fluid for the whole job: new master cylinder, new flexible lines, and new pads. I went with Torque 700 fluid as it is recommended by the local Porsche tuning shop. They prefer it over Motul, apparently.
 

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Discussion Starter #12
Official instructions say 1.5 bar for abs bleeding ( 21 psi) and 2.0 bar (29 psi) for normal bleed. I figured that 23 or 24 was plenty safe.
 
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