StigsBaldBrother said:

That extra ribbing is very interesting indeed. All of the cracks originate in the center 2-3 rows of holes. None of them are cracked near the inside or outside edge.

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That's part of the reason why I'd identify this as only heat checking. Cracks around the same areas in the non-drilled areas confirm this.

Also note that the drilled holes aren't in the same place on the inside and outside faces. Another reason why I wouldn't worry so much about cracks propagating all the way through.

Don't get me wrong, the brakes on this car are amazing. I was just hoping to get a little more track time out of the rotors before replacing. The Boss 302 brakes I had on my 03 Cobra lasted about 12-14 track days and were half the price.

I wonder if carbon-ceramics would've been cheaper per track day... ;D

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I'd still use them is all I'm saying. Like Nick said, "use at your discretion"

This one is beginning to show signs of wear....A little JB weld should fix that right up.

What I find funny is: I do a lot of water main repair. I know.. what does water and brakes have to do with one another.
If we find a small crack on the cast Iron pipe running with the pipe we drill a hole at each end of the crack to prevent further cracking or having the crack run. Then install a full seal clamp and call it a day.

I think the main difference is that the cracks on the rotors are more surface than being 100% cracked. Do slotted rotors have the same cracking issues. If so that shoots my theory out the window. How ever it is a standard practice on water main repairs. Not mandatory but the sign that there doing everything to prevent a reoccurrence.
Thank you for the schooling.

In your pipe example, the hole you drill is preventing the localized tensile stress concentration at the end of the crack which would allow it to grow.

Slotted rotors will still have surface cracks, but not the same size originating near the holes. I've never seen cracks that seem to originate near or from the slot. So not the exact same issue.

By drilling the hole at the leading edge of a crack you are relieving stress's to some degree to stop it, but your right...... cast iron water mains and brake rotors have nothing in common. :

Stig, don't you dbl stint that car with your wife? If so, you would equal more than the normal person's 7 track days...

My GT3 RS buddy's would say that you are about at half life with your rotors. lol You have a good amount of life left in those rotors. As everyone said, just check them to make sure that the cracks do not reach the outer edge of the rotor.

I don't think that solid or slotted rotors will add much life to the rotors, in fact they might have less life than the drilled. Fine tuning the brake pad, rotor and cooling set-up is something that I will be looking at as I start to track the car more. Too much brake cooling can actually shorten the life of the rotors.

Will these small rotor cracks also accelerate pad wear, even more so that just slotted or drilled rotors?

Well Grant 302 went on a tangent again, literally! The key thing is da boy knows what he speaks and I frankly find this the one area I am quite disappointed in the GT 350. This is poseur boy rotors in my estimation, as drilled ones always crack sooner than slotted. The ones shown are fine for now, but knowing my driving style I will chatting with the boys at Girodisc in the future , as I already know I will crack the crap out of a drilled set. Serious Track Rats just need to put in their budget that set numero dos should be slotted.

PS - Girodiscs are made in the good ole US of A, not some overseas Mickey Mouse steel set.

@StigsBaldBrother just curious how many days you got out of your rotors?

Sorry Rick, been on vacation in Hawaii.

Still running them! I got two more days on the track and then decided to make them the street rotors. They didn't get any worse with the additional two days on them, but didn't want to push them.

After checking my front rotors this past weekend I decided to change them. I could feel the cracks with my fingernail and as @Black Boss pointed out to me the cracks were close to connecting so I decided to replace them with the backups I had in my garage. These had 7 track days with 12+ hours of track time plus about 4,000 street miles on them. The rears still look good. This was also my first time using my Caliperfexion studs and sleeves for a rotor and pad swap and they made the job very easy.

http://caliperfexion.com/

In my personal opinion ( and just that) , having been racing for over 36 years and sponsored at one time by a California Brake Company, I really suggest folks get replacement rotors for their GT 350s and others that are slotted , not drilled. I am hard on rotors , but I get a ton more life out of a slotted set than a drilled set. In fact I have only had two drilled two piece rotors ( one from a Company wanting Woodhouse to take on their product), and frankly both lasted with my aggressive style close to half what I got out of slotted rotors --yep , they both cracked , a lot!! I found the rotors that come on the GT 350 as my only disappointment , as I have always viewed drilled as poseur rotors - but they do look fantastic. But Girodisc and others will make a slotted disc to fit our beasts and they will , imho, outlast and outbrake a drilled set. Love you VoodooBoss, but suggest you try slotted the next time around, will bet it will convert you over after you see the length of time before you see those cracks ,etc.

Bill Pemberton said:

But Girodisc and others will make a slotted disc to fit our beasts and they will , imho, outlast and outbrake a drilled set.

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+1

I averaged 8 hours of track time on the drilled rotors versus 20 hours on the Girodisc. The OE rotors are cheap, and from an economics standpoint, it's a close call, I just don't want to swap and bed/season rotors that frequently. That said, I'm hard on brakes and run a lot of tracks that are also tough on Brakes.

The stock rears are fine.

Yes the drilled rotors are not ideal. Not only are Girodisc a good option but the CC rotors are also a consideration plus they save a lot of weight. JAJ is running them with promising results.

https://trackmustangsonline.com/threads/carbon-ceramic-brakes-theyre-on.12573/

In the end for me I went through one set of Pagid RSL-29 pads on the same rotors. So from a cost perspective I'm going to stick with the stock rotors. I'm only going to do 4-5 track days this year and don't expect to do more next year so it's hard to justify the added cost.

Rather than start a new thread, I'll add some color to this one thanks to a conversation at my local Stealership. I have about 2700 miles on these original rotors, and from that they have seen about 5 days, 10 hours of track use with the original OEM pads. We're talking Palm Beach Intl. Raceway, which is not known for eating brakes, as there is one straightaway worth mentioning.

My stealership told me ALL the rotors need to go, of course.

No visible cracks, I've felt them as you've all suggested. They are actually really smooth, definitely no grooving on the face... and I can't feel any noticeable lip on the outside edge.

I'm about to get my caliper out to measure the remaining thickness and report back.... but before I do that what do you think of these pics? Should I even bother?

And why are my rotors so damn rusty for an 18 month old car?

PBIR is definitely not known for eating brakes, especially compared to it's neighbor track.

I wouldn't be concerned about those at all. I don't even see any crack-like indications that look like they could get worse. The OEM pads are definitely on the soft side, thus preserving the rotors from significant wear. I went through the OEM pads in 2 days at Sebring.

The rust is definitely annoying, but is likely a byproduct of good cast iron.

Oh and another thing I wanted to bounce off you all: the Stealership said the GT350 rotors are unique in that they can never be resurfaced, regardless of remaining thickness ...

Thanks @StigsBaldBrother I'll report back with the rotor thickness once my wife looks the other way and I can escape to the garage...

@StigsBaldBrother are you joining NASA at Sebring in October? I've bought an entire spare set of OEM rotors and pads for Sebring... you never know. It's my first time to Sebring and don't want to have it cut short.

I don't think you can turn cross-drilled rotors. At least I wouldn't want to anyways. I can't imagine what the cutter on the lathe would be going through every time it tried to cut across the hole. There's a lot more risk in trying to turn rotors and it isn't worth the cost savings to me, especially on the track and even with plain rotors.

Good idea about bringing an extra set of pads and rotors. I don't go to Sebring without them. Although you probably won't need them your first time there. Memorizing those 17 turns won't come easy and you probably won't be carrying the speed of a veteran.

I'll be at Sebring in October, but with Chin Motorsports instead of NASA. I'm going to try to do a lot more events when the weather cools off, so it's possible that I'll make it to the NASA event. I'll let you know if I do.