Cross drilled/slotted rotors can crack easier. I'd replace them with a new set of 4 from another manufacturer and pull the vdc relay. If the front(s) cracked, I'd be like but because it was a rear, I think the vdc is doing what it can to rein in your G and applying the rears thus heating them up a lot.
Drive around late at night where there's no traffic, don't use your brakes for 5 minutes and come to a rolling stop without applying the brakes. You might need to drive a little aggressively to get the system activated. Feel the rotors front and back. Do it again after you pull the vdc and you will notice the rears are cooler than they were with the vdc in place. Also, remove the shields behind the rotor which I think will allow for better air flow.

 

Not sure I understand. You are saying because the VDC is activating and it's over working the rears?

Well the fronts cracked too, about 3 weeks ago. They are above minimum specification. I replaced them before this trip.

No sorry always a surprise.

 

Oh, the front too? Sucks. Try a better or just different brand. I'd recommend mine but I have no idea how they'd perform under those conditions.
Yeah, the vdc screws with acceleration via the rear brakes and I believe fuel cut off as well.

 

Seems to be a not uncommon thing at all with drilled or slotted rotors. I don't know if if's an issue with the quality of the cast iron, the hole(s) are too close to the edge, etc. They look cool but I personally would never put them on my car(s).

 

This happens mostly with drilled. Issue is they usually drill into normal "blank" rotors that weren't designed to be drilled. So in addition to exposing minor casting imperfections, the underlying "vein" support isn't taken into account, leaving weak spots that crack under heavy stress. Looks cool on the streets, doesn't hold up at the track.
Rotors that are designed to be drilled aren't going to be cheap.

 

Good answer. If the holes aren't chamfered that might be an issue as well. Mines are

 

 

 

 

I'm comfortable with VDC doing it's job lol.

I'm going with blanks this time around. It was cool when I was 21 .

I have an extra one of those I can send you, but shipping is $17.99.

Truth. They were drilled after the fact. I'm not surprised, just disappointed. Not my purchase, came with the sale of the car.

I don't go fast enough to buy real drilled rotors. Slotted is the choice of performance guys, but at $80 more per rotor I just couldn't justify it. Coated blanks FTW.

 

It's still cool and I'm not even close to being 21.
Don't let the bunk rotors sour you on cross drilled and/or slotted. They look great, remove a little weight and in my situation, they did made an improvement in braking performance and stopped the squeal-in-reverse issue, They came with the car so you don't know what they went through previously or if the brakes were bedded/seasoned.
VDC is useless.

 

Changed plugs on the G today, the car has been harder to start recently and last week I pulled a P0300 code. So out with the old NGK Iridiums and in with the new using the same NGKs. I've been dreading this job for a while just imagining how many plugs would be covered in oil, the old plugs lasted 87K miles and the car has 148K. Happily I found oil in only 1, the number 4 cylinder. All 5 other plugs were bone dry and looked surprisingly good for their mileage. And the oil had only progressed down about the top third of the threads and there was no pooling in the plug well. There was a bit on the top of the ceramic portion of the plug but that's it, yay! At least we won't have to worry about valve cover maintenance any time soon. But, the hard start condition is persisting and won't go away, even the pending code is gone. So I am replacing 2 of the hose clamps on the intake because they won't tighten down very well any more and might be causing small leaks. We've replaced both cam sensors in the last several months with OEM so I'm not worried they have anything to do with the hard start. Might be the fuel pump, that would explain why the code didn't return but we'll see. Here's a pic of the plugs 1,2,4,3,5,6 from left to right. I can't believe they weren't more torn up after such high mileage but I'll take it.

 

I'm not certain that chamfering drilled holes has an impact on that. Chamfers are primarily to provide a recess for a fastener head. I guess if one did really "want" drilled (or slotted) rotors, get ones that are CAST with those holes, not drilled in after the fact.

 

I did some research in this area a couple years back and forgot most of it. There's those on either side of the many arguments that is cross drilled, chamfered, cast, slotted, heat displacement, etc. There are an awful lot of performance cars that come drilled & slotted from the factory. There's something to it. For me, as I said previously, I get no more squealing in reverse and a definite improvement in braking, though that may be attributed entirely to the more aggressive pads and besides, I like the way they look.

Here's a quote from a corvette forum I found after a quick search which is well written and I agree with the writers assessment.

" There is absolutely a difference in chamfers....
when holes are drilled at 90 degrees to the fire path, the sharp 90 degree corner creates a "HOT Spot" these corners get 30% hotter than the rest of the rotor. This is cause by angular stress over variable planes. its the effect of drilling that cause the molecules to move closer together at the corners which causes this stress. When stress is relieved or equal , all the molecules are the same distance apart...
A 45 degree chamfer reduces the angular plane thus reducing the Hot spot, so internal stress is less, and this helps with cracking at the angles...no sharp corners

Better than a 45 degree champer is something called a sinus chamfer,
it is a radial chamfer, meaning it doesn't not have a flat plane.. there is little or no Hot spot with a sinus chamfer. So internal stress across the total plane is equal, so when they expand and contract, they do it at the same rate, because there are no hot spots... Casted holes do the same thing... because there are differences in the stress between surface and holes...the whole rotor expands and contracts at the same rate...

Straight Drilled Hole ------------------->

A high stress and heat build up area forms at the intersection of the rotor and drilled edge.

Countersunk Hole ----------------------->

Countersinking increases the external surface area of the hole, thus reducing heat, but still contains edges prone to stress and heat build up.

Radius Hole -------------------------------->

The Radius Chamfer increases the hole cooling area thus reducing heat, but still contains sharp edges.

SP* Sinusoidal Curved and Chamfered Hole ----------------------->

Absolutely no sharp edges. The smooth design promotes cooling and minimizes stress, reducing the possibility of heat checking while increasing both rotor and pad life.

The Sinus-Curve is an example of a design inspired by mathematical principles. Although this process is well known in the industry, it is costly, but it is perfect for those wanting bling for their street car with some spirited braking...
My Eradispeed rotors have sinusoidal chamfers... Not a Baer application, I did them myself...
I hope the pictures make this clearer
Bill aka ET "

 

Neato! Anything for a reasonable price isn't gonna work FWIW. I just prefer blanks or Slots only. If you had brake noise it was your pad choice or high frequency vibration from lack of lubrication/shims typically, IME.

Thanks for your reply about the info, I learned something today.