CMMTracknut

Do you guys run with surface cracks on your rotors? on my fronts only there are the slightest spidering surface cracks on the rotor. they don't go into the material appear to be on the last 1/32nd of the face. I have already ordered new ones but don't want to waste the ones on there now. They have tons of thickness material left. Any advice would be much appreciated.
Thanks
C
PS I run pagid orange and have brake cooling ducts

Sam Lin

Depends on the severity of the cracks, but real minor ones I definitely run with.

Sam

SundayDriver

That is normal and shows that you are actually using the brakes. When they connect the vent holes (or get to that length) it is time to replace the rotors.

Glen

Mark is correct with a couple of additional thoughts from Porsche Motor Sport. The cracks can actually connect 2 vent holes but not 3 and also if a crack gets to the outer edge of the rotor then you must replace. Your rotors are very similar to the ones on the 996 Cup just a slightly smaller dia 322mm I believe instead of 330mm but same material and same construction. We always replace when we see 2 holes connect as Mark mentions just to be ahead of it a bit though, also when the grooving/ridging gets bad(judgement call).

Bill Verburg

Here's what the factory has to say on the subject

mds

Guidance I am using comes from Porsche AG on 964 Cup Car Cast Iron Disks. Thanks to 993_996_enthusiast for the quote:

"Ventilated discs will develop small heat cracks with race use. These cracks will have no effect on braking. Discs must be replace (sic) when three or more adjacent radial holes are connected by cracks or the outside edge of the disc is cracked."

I just replaced the discs on my car. Here is a pic:



Although cracks to not run to the edges, they are starting to connect several holes, so I figured it was time to replace them, especially since my next track day is at Laguna Seca.

CMMTracknut

thanks for all of the advice. I have new rotors so I think I will go forward with replacing them. I don't think the cracks are too bad but I would rather have the piece of mind.
thanks again
C

Greg Fishman

Mike,
Your rotors were definetly needing replacement.

CMM,
Just keep your take offs as a spare set if you happen to need them. I wouldn't replace them until the get close to looking like Mike's.