NC94Vette

So I have a set of Z51 rotors with about 4000 miles of street use and just three days (approximately 300 miles at VIR) on the track. Yep, they are already showing small cracks around the holes.

I have read some of the threads about the good, bad, and ugly of the infamous drilled Z51 rotors and know that they tend to crack faster than solid rotors given the same amount of high-speed track braking.

My question is how long can I run them with the small cracks emanating from most of the drilled holes?

Do I wait until the cracks reach from one hole to another?

Or until the cracks reach the outer edge of the rotors?

Obviously I don't want "chunks" chipping off, but I also don't want to throw them away if they have some more track time left in them since the dog-gone things are expensive.

Thoughts? Suggestions? Help. Thanks.

Z06Fix

general rules

Time to toss when:

Cracks connect holes
Crack reaches the edge
If your fingernail will catch in the crack as you run it across it.

CHJ In Virginia

A picture would really help in determining the status of your rotors. My rule of thymb is - If I can feel the crack when running a finger nail across the area - the rotor is history. Heat checking is normal on heavily used rotors but cracks only get worse quickly !! Rotors are cheap --- wrecked cars are not.

Gary2KC5

small cracks are no issue, even when they are hole to hold (at least for the 1,25" Z06 rotors)

In my experience rotors are good until they actually really crack...as in you can see through the crack (usually from the hub to the outer edge)

928nomore

mid americia has stock replacements for $119 why would anybody risk it?

Bill Dearborn

Mid America charges some of the highest prices for stock Corvette parts. Most dealer parts departments will give 20% off if you talk nice to them.

Bill

NC94Vette

These three photos are the left front rotor:







These three are from the right front:







The rear rotors are fine.

Thanks for all of the comments. These cracks aren't to deep, just concerning that they show up so early. Only around 180 track miles at VIR and on pretty cool temperature track days (7 and 8 Feb) with my newly installed cooling ducts. I really thought that they would hold up better. I am running Carbotech XP10s up from with XP8s in back. The pads held up very well.

So are these rotors good for another 180 miles on the track?

NC94Vette

TTT

CHJ In Virginia

Based on the pics, I think that you have some time left on those fronts. I would not feel uncomfortable running them for another event or two. I would definitely take a spare set to the track next time you go. Examine them carefully after they cool for 30 minutes or so after each run session - the small cracks WILL GET BIGGER.

Racer86

Man, get real. If you are going to track this car, get new rotors, before you have a rotor crack and BREAK at speed. If rotors are too expensive for you, you might want to rethink your track day adventures. Also, you are a danger to others on the track. If I teched your car at a track day, I would not allow the car on the track with cracked rotors. It can happen to you!!

NC94Vette

Thanks Racer. I am not trying to be cheap, nor do I wish to risk my car or those who are on the track with me. The frustration is that these small cracks developed after just one weekend. Six 25 minute sessions over two days. Only 180 total track miles. On nice cool temperature days. With full front cooling tubes.

So new rotors for every weekend? I don't think every car up there has brand new rotors. I do appreciate your point of view and I am thoughtfully considering alternatives.

flink

Drilled rotors are notorious for cracking when used on road courses.

Replace them with non-drilled and preferably non-slotted rotors and
you should be able to keep the rotor costs down to a few tens of dollars
per track day.

gkmccready

"Downgrade" to base C6 or C5 rotors. Then you can use NAPA rotors for $35ea rather than the $85ea C6Z51 rotors. The part number on the caliper brackets (abutments) are 12455800 and 12455799. You'll need to order 2 of each. http://www.gmpartshouse.com/

Racer86

not saying anything about being cheap, just trying to get you to be safe and not get hurt. Performance Friction has rotors for your car. They cost more because they are made of better metal, casting process's and final machining. They have studied the internal fin placement, and their products are used on many pro race cars. CF vendors have high performance rotors can be just as good, but, we have used PF on all the race cars. Be safe my friend, don't cheat yourself on brakes. Rotors don't just crack in the pits or on cool down laps, they can fail big time at speed. Ask me how I know. It was not pretty, and I learned my lesson that day. I was young at the time and knew it all. Spent the next 40 years learning what I did'nt know back then. Enjoy your track days, great fun for sure!