Falcondrivr

So I have 2 track days and about 2000 miles on brand new factory rotors. I had them cryo treated to see if it would help them last. I just noticed that cracks are starting from the holes... cracks are about 1-2mm now so I've got some time.
Here's the question;
Some of the guys I track with have gone to cheap knockoff rotors for the track. None of them in a 993...Has anyone done this? I can get some brembo non-drilled ($79), or Bendix drilled ($59) rotors, and switch them out for track use. I know they'll squeal, but I use Performance Friction 97s for the track. My car sounds like a school bus on track days anyway...
I guess my question is about the performance and safety of these cheaper options...
http://www.autopartswarehouse.com/se...%26+Components)

George from MD

Small cracks are fine and normal. If they are close to the edge you'll want to get new rotors- but by that time you'll probably have worn the rotors out anyway. I've tried cheap rotors- they don't hold up anything like an OEM rotor. I'd stick with OEM and save your money on the cryo treatments- IMO that's BS. You can switch your pads out for track days but I've never heard of anyone switching out rotors.

Falcondrivr

That's just it. I'm thinking that it would be cheaper to buy the cheap rotors and use them up in a weekend, then switch back to the factory rotors for street duty. If I'm only going to get 3 or 4 track days out of the factory rotors. I'm already switching pads, what's another 30 minutes or so?

Phil

3-4 track days out of a set of OEM rotors? I've never heard of that. From personal experience I never had to change the rotors when I was active in DE's Over two yrs worth of 1 or 2 times a month.....

certz

3-4 days does sound abnormal. I typically get 12-16 track days out of the OEM rotors.

trophy

When I had stock rotors and Pagid blacks I would get a whole season out of a set of rotors (30 to 35 track days). With the big reds I now get 2 full seasons out of a set of rotors and pads.

Heat is what damages the rotors both a lack of and too much, all track type pads have a very specific heat range that they work within. If they are too cold they wear the rotors very quickly if they are too hot they crack.

PFC97's are also particularly hard on rotors.

I am sure Bill will chime in here as he is the Porsche brake expert.

GT3 Tek

I personally would not cryo track rotors, like tires they are disposable and need to wear to give the stopping power they were designed for. In the past I have found cryo rotors I used with pagid orange (R4) pads lasted a long time (4 POC Cup race events) but lost stopping grip because the surface polished due to the hardness.
Most cross drilled rotors used in track events will develop small cracks around the holes due to heat but is not a concern unless they start cracking hole to hole which is why I ran slotted rotors with extra brake cooling after my experience with cryo cross drilled.

Joel

Bill Verburg

I know one guy that does a lot of track days, he is using Coleman 322x32 w/ stock hats from oem 993tt 322x32. He is very happy w/ them. But this is a Big Red replacement rotor.

For stock 993 you would want 304x32, I don't know for sure that Coleman has them but my guess is that it is likely as 304x32 was stock size for the 930s and they sell a lot of those. The big question would be the hat.

Willwood may have something in that size too.

Falcondrivr

So how far along would you guys feel safe on the track with rotors cracking? I changed out my last ones when the cracks were about 5mm long. the weren't connecting the holes, or going to the edge of the rotor. MAybe I'm just paranoid about blowing up a rotor?

JPS

There is a recent thread I posted pics on that show you right at the point you need to swap them out. Search for brake rotor and JPS. A couple peeps felt I could get a day or so more, but most said that was the point they would switch them out.

In my experience you get small cracks the first day you use them. Then from there with more heat they slowly grow, but not at the same rate as on that first day.

Go to Sunset or FDMotorsports for the rotors...not much more than your knockoffs, and they are OEM.

Falcondrivr

Thanks JPS!
It looks like I may have prematurely taken off the first set. I guess I have 2 serviceable sets now.
These are on the car. 2 track days and 2000 miles street. They are the cryo treated ones:

These are the old ones: 10-12 track days. However, those are days starting in green with stock pads, working up to solo with the PF 97s...



I love the performance of the PF97s. But they do seem to be hard on rotors. Right now, I'm not sold on the cryo treatment. It doesn't look like they are lasting any longer than non-treated rotors.

NP993

Those rotors are fine.

Steve Weiner-Rennsport Systems

Hi,

Cracking issues are, quite obviously, the result of excessive heat so reducing the heat load at the front should be the first order of business.

There are several ways to accomplish this and we've had really good luck over the past 14+ years by installing more aggressive pads on the rear to get them doing more of the overall braking. Plus, this also improves the brake bias on many OEM braking systems that have excessive front bias, leaving the rears to do little.

One needs a certain degree of experience with the various pads to understand compatibilities, however a good setup for your car is either Pagid Orange (RS 4-4) or Yellow (RS-29) up front and Pagid Black (RS-14) in the rear. I've used those quite successfully in cars just like yours.

Those PFC-97's are pretty aggressive pads and are adding to your heat issues.

Naturally, JMHO,..............

Falcondrivr

I'm running stock pads in the rear. if I go with a better pad, does the bias "adjust" by itself, or do i need to do something? The car sheds speed fine. But I was wondering if I had the fronts doin too much.
Also, I have looked for the duct kit, as I have a turboS front bumper. Can I buy just the needed dust shields somewhere? Aftermarket? I have the high temp hoses at the hangar...

VNTGSPD

Hmm. This may not only be exacerbating the cracking issues but also leaving time on the track! You should at least have the same pads all the way around or listen to Steve (duh?) and go with something more aggressive in the rear.

My limited experience shows that the rear weight bias of the 911 allows it to respond VERY well to increases in rear brake bias (hydraulic or via pad changes).