IanM

These (M030) rotors have served me well. I can't remember how many track days, but there have been plenty. They are OEM Porsche rotors that I had "frozen" at Diversified Cryogenics. They have lasted way longer than other rotors I've had, still work great and are not warped. Problem is, I'm getting a bit nervous about all the surface cracks in them. Is it time to throw these things out? Note than none of the cracks extend to the outside edge, but some of them can be felt with my finger nail. I'm sure they're wearing my front pads out much quicker than usual.

chris951

Dang! I've never seen that on a solid rotor before, seen it on x-drilled ones.

IanM

Yes, pretty nice, hey? My local track has short straights and slow corners, and the brakes get extremely hot. I'm running PFC01 pads / RBF600 fluid that seem to be up to the task, and big brake cooling ducts.

SirLapsalot

I've been told if you can catch a finger nail on any cracks or they extend to the edge then retire them.

Eric_Oz_S2

My S2 rotors have the same crack pattern - as did the last set. It happens fairly quickly from new. I work the brakes very hard (track car), often slowing from up to 220 km/h to 80 km/h at maximum braking. I have seen this on other 944s and 968s as well (even those with big blacks/reds). I suspect it is also a function of pad type, with race pads being worse due to the higher temperatures generated on the rotors (I run PFC97s). I suggest keep an eye on it, but don't be too alarmed unless they start to open up or extend to the edge. Also, don't wait until the discs reach minimum thickness to change them. It is probably best to change the pads and rotors together.

JDS968

This seems to happen when you are running a race pad (such as your PFC01s) at proper operating temperatures, such as on a track-only car that never sees street driving. Properly bedded in, the pads transfer a layer of material to the surface of the rotors that does not get ablated, and therefore most or all of the wear happens on the surface of the pads rather than on the rotors. You see the pads wearing faster and little or no rotor wear. With the rotor surfaces experiencing heat cycles without getting ground down, they develop cracks like this. If you can catch a finger nail on them, I think maybe it's time to change them, but it's hard to say without seeing them in person.

jerome951

If none of the cracks extend to the outer edge you're OK, but you don't have much time left on those maybe another weekend). Be sure to check the backside, too. Take a set of spare rotors to your next event just in case and inspect them after each run.

mikey_audiogeek

That'll buff right out...

IanM

Thanks for the feedback. I've just ordered a new set of front rotors (Sebro). FYI, rears are not cracked. I'd like slotted, but the only ones I know who make them are Zimmerman...and I wasn't happy with my last pair of front Zimmermans (warped after two track days).

Anyone know of any other slotted options for M030 front rotors?

mikey_audiogeek

http://www.frozenrotors.com/shop-by-...+rotor+format/
I'm guessing you've considered the ones from Diversified Cryogenics.
Dunno who makes them though.

Can they slot OEM ones for you?

Eric_Oz_S2

I have used cryo treated rotors before. I'm not convinced they make any difference.

Oddjob

I dont see anything in the pictures that look unusual for track use, or anything that indicates they need immediate replacement. Still look ok to me and could get some more use out of them if you want. Primarily light surface cracking, or "spider webbing". I run my rotors further than that, until it cracks thru to the edge or until I can get my finger nail actually into the cracks, not just feeling it.

But never a bad idea to have a spare set of rotors on hand in the box of track spares.

I don't like Zimmerman rotors either. W/ the M030/Turbo S rotors, metallurgy is not the same as the factory Porsche rotors. In a side by side test (left front Porsche, right front Zimmerman), the Zimmerman cracked thru way before the porsche rotor did. This has been confirmed by others too.

Vast majority of all pedal vibration is due to overheated pads depositing material onto the rotors, not actually warping the rotor itself. Some pad brands and compounds are notorious for doing this.

The cryo treating does help, but comes down to economics of it. May make the rotors last 25% longer, but costs 30% more to have done.

If looks dont matter, run solid (non-drilled, non-slotted) OE Porsche rotors for the best all around performance per dollar.

2bridges

looks like a typical track car rotor. Nothing alarming.
I wouold keep an eye on them but would continue running them.

zerMATT951

+1 on the pedal pulsation/vibration cause

...and here's a good read from StopTech on that topic that some of you may have already seen. I think it does a great job explaining what's really going on:

http://www.stoptech.com/tech_info/wp...rakedisk.shtml

m73m95

This.

That is just a little heat checking. Not "cracking".

Maybe go over them with some good aluminum oxide sand paper to break the glazing off, and run then again.