Yes, Yes, I know... I am, but thought I throw this out for feed back.
Coinsidently, a few weeks before Road America this past Labor Day I warped my stock rotors. So perfect timing for a new set of "Frozen "Rotors, and we ( My Tech) tryed a set of Performance friction pads( not sure of the color?) for the event.
Well after bedding them in I ran the 1st two sessions there, and had to bleed the brakes (already?) By the second day same thing, but worse. I was getting a lot of vibration in the front end upon track type braking (the rear view mirror shook quite a bit too). By the end of the 4-days things smoothed out a bit??, but never came back to "normal".
Onto Watkins Glen .... same vibrations are back. ( so's the fading /wearing of the pads) and more brake bleedings than I've done all summer.
It's in the shop now & expect to know more tommorrow.

Various things have been suggested, like:
The/A rotor is already warped.
I'm hitting the 'threshhold" of the ABS(and don't know it?)
My little RUF chin spoilers not letting in enough air to the scoups
$hitty pads?
Feedback please.
Bill

 

I'm no expert, but I had problems with repeated "warped" discs realier this year. 3 sets of discs, OK at first, would get progressively worse over a few hundred miles.

I had the discs skimmed ON the car - this mainly overcomes hubs which are slightly warped. Car has been fine since.

The main symptom for me was the fact that a new set of discs would feel fine at first, but then get worse.

 

Rob, Interesting, any track time? Or street miles?, Were you able to return them for another set/s at no charge?
My brakes are fine for "normal" every day stuff stops, but going from 140 to 60 ASAP is when they shudder.
Bill

 

Bill,

Try the Hawk Blues 9012. Vertex auto sells them for about $110/axle.

The only time I had the "warped" rotor feel you described is after using the Pagid Oranges. They don't like it when you bed them in improperly and are very unforgiving.

After installing some PO's before a big track weekend, I dropped my car, jumped into the driver's seat and released the handbrake. Since I was on an incline, the car started to roll a little. Of course, the pedal pressure was nonexistent since I had just pushed in the pistons to swap pads and after a few frantic stabs, I built up enough pressure to slam the car to a hault--big mistake!

After the second day at good ole Road America, I started to feel that thumping coming into T5--not a great feeling at 130 mph. My instructor said it was a warped rotor but, like yourself, I thought "Hell, these are brand new rotors."

A close inspection of the rotors revealed some imprints the shape of my pads. Houston, we have a problem.

To fix the problem, I employed the Hawk Blues. This particular compound cleans all that crap off and gets rid of the "shudders." They're also a fantastic track pad and IMHO perform as well as any of the popular options, i.e. PO's or PFC97's. The only down side is that they emit a toxic brake dust which can be a little stubborn during clean up. It's a small price to pay when you consider the expense of new rotors--again!

Here's a white paper on the topic written by Carroll Smith. Basically, ole Carroll agrees with me.

 

Bill,

A couple of thoughts. What you're describing sounds like the problem some have had with Pagids with brake pad deposits on the rotor - gets worse as things heat up. However, PFC says their pads shouldn't deposit like others. Also, sounds like you're generating more heat, hence the frequent brake bleeds. While your mechanic prefers PFC's, maybe you should go back to what you were using before? If you haven't read it already, there's a great article by the late Caroll Smith at the Stoptech web site, under 'technical' that describes why deposits form.

If you still have 964 brakes, you can get from Seine Systems a titanium shield which slows heat transfer from the pad to brake fluid. It goes between the pad and the pistons.

If you continue to use the new pads, you might consider moving to cast-in hole (as opposed to drilled, which you want to avoid) rotors, which run cooler than solid rotors. If you have stock 964 brakes, you can get them through Vertex, then have them frozen. If you have a brake upgrade, you may be able to get a Porsche rotor (which have cast-in holes) from Diversified Cryogenics already frozen. Note your mechanic really dislikes hole-y rotors, as they will eventually crack between the holes. However, cast-in holes will last quite a bit longer than drilled holes. Of course you can replace the fog lamps with a kit to route air to the wheel well, to assist in brake cooling. Some like to run Pagid Blacks, like the 964 Cup cars, which has a ceramic compound with lower heat conductivity.

I've run Pagid Oranges for years, always broken in properly, on slotted front rotors, and haven't had any deposit problems.

 

Are you allowing a cool down drive before stopping. I have read this promotes even cooling and helps stop warping.

 

Joey's link is well worth the read. I like the theory.

FWIW: I use normal pads and the only problem I've had is a squeal in the front pads after about 100 miles, which disappears the moment I spray the brake area with water. I had absolutely no problem on my recent DE either and there were plenty of heavy braking sessions that day.

 

Track time since the skimming - everything fine.

Your problem sounds different...I could feel mine even at walking pace.

Hope you get it sorted

 

Hi Bill,

Have you checked for corrosion under the caliper plates?? I have a horrible vibration at various speeds when applying brakes from the front-end. I have replaced my OEM discs twice as I thought they were warped but no joy!! A couple of P Car specialist have said this could be the problem.

Regards
Gary

 

While cool down is important, almost equally important is not using your brakes to stop when you park coming in off the track. When you do that, your brake pads remain on the very hot rotor. Recommended approach is to sneak up on your parking spot in first gear, and just prior to stopping, push the clutch in, gear still in 1st, turn the engine off, and feather the clutch to stop, without the brakes. This is difficult to do if you back into your parking space after a run.

 

I have Performance Friction (97 compound) pads and they've been great.

I used to have always problems with stock pads, boiling the brakes etc.

Now with PFP's I have nothing, they stay constant and give good braking thorughout the 30 minute session in Florida heat at Sebring (which is notorious for brakes).

I did ad coolong ducts also which cool down front temperatures quite a bit so I can't say how much is because of ducts & how much for pads.

I know other 993 guys who use PF Pads at track and are pleased with them. There are different compounds though, what do you have?

 

Joey, the "White Paper" is a great read! Thanks all for the input. FWIW the Rotors are Vertex, Frozen, Pads-Performance friction-#97. My Tech is checking(as I write this) for cracked hubs, corrosion and claims a few more things that have'nt been mentioned. Hopefully he get it sorted fairly quickly.
I also believe both Rotors and discs were bedded in per "the White Paper".
I do have one Dark Horse tho, my other half.......She swears she does'nt use the brakes to come to a stop in the Paddock! Her instructors say she Won't go over 110 on the straights!
Will let you know how it Shakes out. ha ha!
Bill