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Hello -- This is my first post after years of lurking. I've really benefited from the wisdom shared here.
I've got a track event coming up this weekend, and I'm debating whether to replace the front rotors. They are heat checked and are beginning to show very small cracks, but no terminal cracks reaching the inner or outer edge. The small cracks can be felt with a fingernail, but are still quite shallow and small. The inside of the rotor rings look less crazed, so this is more a concern for the outer face.
The event this weekend is a time attack and at most I'm expecting 80 minutes on track. Of note, I think my calipers are toast and may be dragging a bit, which may be compounding the issue and adding more heat. I plan on rebuilding them after this event.
The rotors are DBA 5000 Series T3, so I'm not too worried... And, I know I'm the bazillionth person to seek an opinion here and elsewhere...
My opinion is that I can run them another full track day without much worry of them failing/cracking outright. Am I being risky? Should I just put new rings on at this point? I humbly submit myself to a sanity check here.
It depends how aggressive you are planning to use your brakes. I would use those rotors on the street without hesitation, on the track, maybe. Ambient temperature, track layout and the nature of the event would also influence my decision. I would check the rotors very carefully before and after each session, avoid full on braking and have at least 2 warmup and cooldown laps w/o brakes. Most track tech inspections would like to see more than 1/2 pad thickness and fresh brake fluids, also.
I ran rotors with small cracks like that on the track with my C4 ZR-1 and they became large cracks coming out to the edge of the rotors. It was very evident, you could feel it and hear it before I pitted and called it a day. Driving home for 2 hours on highways was a non-event. These vented, double rotors are pretty robust.
Heat checks like those were pretty normal for me after 2-3 track days with a C7Z. Rule is to replace when the cracks reach the edge of the rotor. I typically got 8-10 track days out of a set of rotors, less as I got faster and pushed the brakes harder.
Good thing is DBA are cheap right now, only about $300 a piece for the rings.
What pads are you running? There's a lot of pad smear on the rotors.
This might be my issue. I may be going too fast on my out laps.
Heat checks like those were pretty normal for me after 2-3 track days with a C7Z. Rule is to replace when the cracks reach the edge of the rotor. I typically got 8-10 track days out of a set of rotors, less as I got faster and pushed the brakes harder. Good thing is DBA are cheap right now, only about $300 a piece for the rings.
What pads are you running? There's a lot of pad smear on the rotors.
This is after five track days, which is partly why I'm hesitant to trash the rotors.
I too subscribe to the advice that one generally wants to keep going until the cracks reach the inner or outer edge. It just feels counterintuitive when you add everything up, including the safety factor.
Running EBC SR11 pads. I believe I've seen another vette on here using EBC SR pads and they have similar smearing/transfer. Wonder if they are getting too hot, though.
My last track event my AP rotors looked 10 times worse than those and I ran them for two days with two drivers driving the car on one of the days. The rotors don't look any worse now than they did before the event so I didn't use the brand new set I had in the tow truck.
Run the rotors but keep an eye on them during the event. From your pictures it looks like you have several more track days you can use them. I usually run rotors until the heat checks are larger and much closer to the inside and outside edges. Are you running the GM front cooling ducts that GM started shipping with the wide-body cars in 2017?
Really appreciate your opinion here, Bill. Thank you! I am going to go ahead and leave the rotors on for at least another track day and then keep a close eye as you've suggested. I need to also be much more careful about warming up and cooling down.
I'm not running the 2017+ cooling ducts (my car is a totally stock 2015 M7 except for brakes, wheels/tires). After doing some searching, it sure seems like those are effective compared to the basic duct/deflectors.
Those rotors are even close to being done! The crazing/microcracks are perfectly normal. Run them until the slots are gone are they start to crack through at the inner or outer radius.
Time to replace rotors?
