On my last track day before yesterday I had brake pedal vibration and felt it in the steering wheel. It only occurred after getting the brakes hot and doing one or two hard slow downs after 130+ on the main straight at Thunderhill. Then they would vibrate for the rest of the session until they cooled off. The pattern repeated itself during each session.
After that track day I replaced the rotors on all 4 corners with Sebro slotted rotors and replace the pads again with another set of Cool Carbons. They were well bedded in and never vibrated at all on the street. Yesterday at the track they did the same thing as my old brakes. They feel like they warped after my first session on the track. After one high speed braking application the brakes vibrate and the steering wheel shudders during subsequent brake applications. They actually vibrate the most when pressing the brakes with medium pressure and less under maximum application.
Could they have warped instantly? On the drive home and driving today they feel fine and don't shake at all but it is very frustrating to lose confidence in your brakes at the track.
What could it be if not the rotors?

 

Could also be pad transfer. Many guys use Hawk Blue pads and it generally cleans it away. Very harsh pad . If you run with the Hawks and have a no issue you will know and can try a different pad.

 

+1, I'd say pad transfer or pad material issue

 

Cool Carbon pads are your problem. 4 years ago I tried a set and they did the same thing. Bad judder. Ran them for two track days and they completely disintegrated. Worst pads I've ever tried. Like the name implies, they only work when they are "cool". Maybe OK for C&C duty but won't work at the track. Go with PFC...

 

I have had no such problems running Pagid Yellows at Thill and Luguna with otherwise stock brakes and racing fluid. I've also switched to Sebros due to cracking in the stock rotors hoping for longer life.

There is no streetable pad that will survive 996TT speed/weight at Thunderhill, so resign yourself to race pads and hi temp fluid for track days. I can' t speak for the PFC recommended above , but have found the Pagids to be reliable and robust.

The real problem is the stock brakes just barely suffice once at speed. It works, barely, with yellows and RBF600 so long as you have some brake ducts and are very diligent to take cool down laps. Remove either of those, like an unexpected trip to the pits or black flag, and you're boiling fluid.

 

I agree with the Cool crapbon pad issue.
Like Pwdrhound says. Go with the PFC pads
If you are going to be tracking your car at all go with the 08 compound in both ends or 08's front and 11's in the back to get some more bite in the back.

 

Ferodo DS 1.11 are great pads too.

 

perhaps switch pads for the track and always use a racing pad. I use pagid and hats form racingbrake.com and no issues stopping from 145 at the glen

 

+1 on PFC

 

PFC 08/11 here

 

I didn't mention it but my old pads were also a pair of Cool Carbons. I replaced them before my first track day 18 months ago and the exact same thing happened...as soon as I got them hot they would make the car shudder and shake. I mistakenly thought I needed rotors. Driving to work today they were fine so I guess I'll use them for now and definitely get some PFC pads before my next track day.
They are so smooth when cold but once they've performed one high speed stop they are just awful until they cool off again!
Thanks for all the useful replies...this kind of thread is why I still think 6S0 is a valuable place.

 

Why not run track pads and change out when back to street?

 

That is exactly what I plan on doing...leaving on the CC pads and swapping before the next track day. This makes the most sense to me since I'm guessing that track pads are probably noisier, dirtier and harder on the rotors than street pads.

 

I see then you have it covered lol hope it works well.

 

The PFC work just fine on the street.