sergeyk

At what point heat checks become a problem and rotors need to be replaced?
So far I gathered 3 answers:
- cracks reached edges of the rotor;
- finger nail can fit into crack;
- if drilled rotor (like mine Z51) crack from one hole reached another hole;

Any more criteria?

John Shiels

cracked edges for me. More cautious then sooner.

Bill Dearborn

Cracked to the edge either drilled or solid rotor. I would replace the Z06 drilled rotors if there was a crack starting to run toward the edge from one of the outboard drilled holes. Cracks between holes didn't warrant replacement.

Bill

sergeyk

Bill, the explanation I got for replacing rotors with cracks between holes is that rotor can grenade.....

Joy of 6

I think your 3 points are all valid and important

CHJ In Virginia

I probably am a little more conservative than most folks. If the rotor has a heat check crack that I can strongly catch a fingernail in, I usually replace them. Small ones don't matter much, but if the crack is approaching the outer edge of the rotor I replace them. I really don't like to replace brakes at the track, it's a PITA and may cause you to miss a session. Rotors are cheap - track time is not.

UstaB-GS549

If I can see a split or feel a crack in the pedal it gets replaced.

I visually check before going out on track, but have had occasions when I didn't see anything, but felt it after the the 2nd or 3rd hard brake application. Pit in. I think I can change a front in about 5 minutes.

It's very important to not to ignore the telltale vibration from a crack.

Bill Dearborn

I hadn't heard that but I also didn't have any issues running the rotors that way. On my C5s I could feel a crack developing as the rotor would start to thump a little and then thump badly when it cracked all the way. I did notice after one hot session that one rotor had like a thin line shaped bulge on the surface. After the rotor cooled that bulge had turned into a crack.

On my C6Z I have not been able to feel cracks in the rotors. Have had all 4 crack multiple times over two years and haven't felt a single one. Most have cracked while I am on the track with only a few cracking while the car was cooling down.

Bill

Rag Top

I was also told the finger nail catching on a crack theory.

I was also advised by a brake guy (that works pit at Cup events), not to use my drilled rotors that developed heat checking at the track. (that grenade comment again.) He was not selling me new rotors (I already had new ones), I was just asking if he thought I could run them at the track.

When in doubt–replace. Rotors are a lot cheaper than hitting a wall/curb/other cars.

mfquinn

I wish I could remember the forum member that made fun of me because I said that I had a seperate set of rotors for the track. I explained that I didn't want to use the factory drilled Z51 rotors on the track for the same reasons you folks listed and was blasted for my opinion. I prefer to change the rotors and pads at the track as the DTC pads destroy wheels (but they stop very well).

It is pretty easy to know when to replace the fronts as they tend to spyder and then start cracking. But what about the rears? I only get a little spydering on them. I noticed after my last track event that the edge was higher then the rotor where the pad hits. I wasn't sure how to check the thickness to tell if it needed replacing so I just bought new ones.

sergeyk

5 min won't be enough unless you have trained team.

- remove wheel, 5 nuts
- remove calipers, 2 bolts
- remove bracket, 2 bolts, but tough to get bar-breaker there
- remove retaining washers
- remove and replace rotor
- reassemble in opposite order and torque to spec;
- repeat other side

more like 30min...

brkntrxn

I don't replace rotors until they are cracked to the edge. Then again, I run NASA TTA if that explains anything.



I will politely disagree with you, at least for my C5Z06:

NASAblue

I can change the rotor fast as a jack rabbit. I could do it in 10 minutes, finish a beer, and be looking at the cooler.

One weekend I went through 3 sets of stockers!

Bill Dearborn

You forgot to add in the time to jack the car. With my C5Z on R compound tires the car was just low enough I had to use two boards under the wheel to get the car high enough for the jack. Monkeying around placing the boards and then driving up on them and then getting out and jacking the car took several minutes.

Bill

brkntrxn

Bill,

Although I made cradle supports to jack from the front and rear cradles, I just jack the car from the sides about 90% of the time.



-Kevin

RX-Ben

I also for wait until they crack - they can go a while after developing a number of heat checks.
But I also TT.

JimbeauZ06

I agree with John but I also would say it depends on what point time we're talking about. If the rotors have fairly wide cracks prior to starting an event I put new ones on. Once I'm at the track I run them until they crack to the edge. "Heat checking" or "spidering" is common and not cause for major concern. Once you can hang your nail on one they need to be monitored more closely.

2000BSME

I replace mine after I hear a "tink" and find that it has cracked through.

drivinhard

fixed

Jason

All Rd Atl TTA records havebeen set on at least one cracked rotor. Makes you scared to brake.