JimbeauZ06

I've got my Z06 in the shop doing my pre-tech inspection for VIR this week. The mechanic calls and tells me my rotors are cracked.

Now I just had them off this weekend installing new hubs/bearings and pads, and I noticed some very fine/tiny surface cracks that barely looked like they were deeper than the thickness of a sheet of paper. They definitely weren't deep.

Is this a problem? These are the normal $40 NAPA rotors that everyone recommends with maybe 7 track days using Hawk HPS pads.

Thoughts?

johninar

sounds like spidering. I don't usually run them on the track at that point. The ones I have on the car have been that way since my last track day in October. I'll be changing to a new set this weekend in prep for first track day of the year.

I'm sure others will chime in with their experiences.

Good luck and have a fun/safe weekend at VIR

ccj

Without a picture of said cracks its tough to tell. But rotors that see track use will always end up with those. When I was running stock rotors (moved up to a stoptech kit) I would typically replace the rotors at the beginning of a typical track season (6-7, single day events for me) regardless of the extent of what I call 'crazing cracks'. It sounds like you have that many track days on the rotors already, so I suggest changing them out and then keeping one of the old ones to get you home if you really crack a rotor at the track and don't trailer your car.

The above is assuming solid faced rotors, not crossdrilled.

MungoZ06

Sent you a PM with link to some pics of extreme spider cracks ...

JimbeauZ06

Thanks guys. "Spidering" is exactly what it is.

Ordered new rotors just now. Looks like despite my best efforts to get out in front of it I'll spend the night before I travel with my car up in the air!

Small price to pay, right?

Aardwolf

Good idea to replace them now. Tossing new rotors on only takes 20 mins though.

drivinhard

At 7 events, I'd put them in the "spares" pile. VIR is not a place to fart around with iffy rotors.

longdaddy

as others have said, at a point that kind of cracking starts to happen, I usually replace, although I know I can get another day out of them.

Kanmer

My question is...is it cracking or heat checking? If it is heat checking (which is normal) I would run them. You will get heat checking through hard braking and heating and cooling to extremes. This will not hurt the rotors and is normal. What you have to look for is anything that catches your fingernail as you drag it across the surface of the rotor. If you have any heat checks that extend all the way to the outside edge then trash the rotor.

HTH
Bob

argonaut

^ I agree. I've asked this question numerous times and have always been told not to worry about spider cracks (heat checking) until you can catch a finger nail on them. But...I always take a 2nd set of rotors with me to the track so I can swap if needed.

BEZ06

Below are a couple pics of a rotor I ran hard at a high speed HPDE and they were doing a lot of braking from 165 - 175 down to 60 or so with DTC70 pads and Hoosier R6 tires. You can see the surface spiderweb cracks, and in the first picture you can see a couple of more pronounced cracks at the 3 o'clock position. Of course there's a big crack all the way through the rotor at 12 o'clock.

These are off a C6 Z06 and are DBA 4000 rotors. I wish I could find some just plain solid rotors for the C6Z, but these are the best I could do. You can see how the rotor cracked right at the slot - the slots (like holes in the stock C6Z rotors) create a stress riser point that will focus the stress and crack at the slots or holes.

Bob







.

the blur

I find once they get heat checked, they last even longer. it's like a tempering effect.

JimbeauZ06

I agree with being safe and not "farting around" at VIR, specially since it's my first time there, and it looks like rain.

Having said that and after looking at some others pictures I think these fall in the "heat checking" category. My new set came in so I'll have them with me if needed, and while it takes me longer than 20 minutes to replace a set, it doesn't take that long if I need to.

I appreciate your insights.
Thanks!

Jason

If it's going to be raining, *I* would definitely run them.

whosurdaddy

Sounds like a good call. And NWS is calling for only a chance of light rain. I'll see you there with my fingers crossed......

Jeff Bernatovich

Quick rule of thumb. If you can get your fingernail stuck in a crack--the rotors are gone. Of course the picture shown with the pronounced crack at 12 o clock can only be used as paperweights.