Prior to this weekend, the car had 2,700 miles including one track event at Barber Motorsport Park. I don't drive the car very often, but about 3 weeks ago I noticed that the brakes had that "glazed over" feeling. On Friday I went for the preinspection and found approx 3-4 mm cracks in the front disc, and brake pads that looked like someone took a torch to them. I mean ugly, bubbley, black and rust looking pads!

At this weekends PDE event, the brakes (as you would guess) didn't work very well. The holes in the rotors would fill solid with brake pad dust after every run and the cracks are now approx 5-6 mm's.

My questions are: 1) Is this normal? I spray Simple Green on the tires and wheels before I wash the car. Could it react with the pad compound?

2) Mechanic says Porsche allows 10 mm cracks, so long as they don't play connect the dots! Should I go ahead and replace them now?

3) If I can't deal with brake squeal around town, should I go with the factory pads again, or does anyone know of a higher performance pad that doesn't make noice?

By the way, I was shocked that I was only averaging 6.4 MPG on the track, untill the guy in the 2 liter Mit Evo told me that he was getting 5.0 MPG.

Thanks,
Philip

 

The problem lay with the pads, not the stock rotors. First change the pads and next fluid, also remember to allow the cool down lap.

 

I agree, it sounds like the pads overheated. Try RS-19, they work well at higher temps, but the price is some squeaking. Once cracks connect three or more holes or the outside edge is cracked, it is time to replace the discs. The pic shows one that needs replacement.

 

Also not all metal discs are created equal, at least the APs and the race brembo discs are allegedly much better at handling heat cycles then stock discs due to different metallurgy. However, I am not in materials science so I don't have direct evidence of this, just hearsay from my friends that run the AP discs.

 

Its really the drilled issue. I think slotted is a better solution for heaving driving.

 

Has anybody tried chamfering the holes on a new disk?? It may slow down the cracking by eliminating the sharp corner around the hole. carl

 

As far as I know they are casted with holes, not drilled.

Ciao,

Johannes E.

 

You could still take a drill bit and put a small chamfer in them to brake the sharp edege. Some drilled rotors come that way to reduce cracking. carl

 

I went through 2 sets of front rotors last DE season on my '04 GT3. Had a set installed this week and was advised by the race shop to have next set cryogenetically frozen. It is supposed to increase rotor life (i.e. cracking) 2-4x. Apparently there are places that do this (Frozerotor, for example). Anyone with any experience on this?

 

i think cryogenic freezing is a gimmick. brake rotors at least