CorvetteZ51Racer

Hi all. So now that I've cleaned the vomit up off the floor of the garage....

I did an HPDE two weeks ago down south on a 105 degree day. Car ran great in the first session. Second session, the ECU wouldn't let me turn the active handling all the way off. Was holding down the button for 5 seconds, then 10 and it still wouldn't turn off. TC only. So I figured "this won't be THAT bad, I'll deal with it and figure out before the next session". WRONG, bad idea. After going for a ride through the infield at 140 when my brake pedal went to the floor from boiling 2 day old Motul RBF, I limped the car back to the pits. At this point I found a few problems which took me a while to fix, but I was able to get the car turned around and back out on track for the next day.

Well today I got around to REALLY tearing into the brakes and found some lovely things (I'll post pics later). Rotors are shot (cracked), brake pads overheated and chunked, EVERY seal on the calipers is cooked into oblivion (I think my last Thanksgiving turkey wasn't even this bad), and the tie-rod end boots are cooked.

Short version: Anyone know where I can pick up a rebuild kit for these calipers and new tie-rod end boots? I've Google'd and all that junk and can't find anything yet.

gkmccready

Seals or dust boots?

CorvetteZ51Racer

I know the dust boots are shot, but considering the fact that the brake fluid reached at least 540 deg F (according to the temp strips - the boiling point of RBF is somewhere are 594), if I'm going to start taking them apart, I'm going to go through them completely.

gkmccready

I *think* Randy@DRM posted in another thread what the part number is for the C6Z brake rebuild kit... try a search and you might get lucky.

CorvetteZ51Racer

Thanks. Looks like I found the thread where they were talking about it.

gkmccready

http://forums.corvetteforum.com/auto...6-product.html

I missed the one with the rebuild kit, but found the one with the SS pistons. ;-)

CorvetteZ51Racer

The pics I promised


















MENTAL NOTE: IF YOU CAN'T TURN OFF ALL THE NANNIES, STAY IN THE PADDOCK UNTIL YOU CAN GET THEM TURNED OFF!!

dfinke23

What pads were you using?

0Randy@DRM

As of two weeks ago, still no GM rebuild kits in stock anywhere. Without going into all the details we maybe waiting a bit longer.

Randy
PS will check again on Monday for the latest.

CorvetteZ51Racer

Cobalt CSR. I have to admit, they held up well until the fluid boiled. I put temp strips on my calipers and temp paint on the rotors. The rotors were somewhere between 1550 and 1700F. Those pads are only recommended for use up to 1200F (by some sources, 1000F by Cobalt).

Since this happened, the car has gotten brake ducting, and I will never again go out on course with the Active Handling still enabled. My first session, when the AH was turned off, my rotors only hit 1100F.

CorvetteZ51Racer

Randy, thanks (I think). I was going to send the calipers off to Mike to get powdercoated, and may see if I can buy the stainless pistons from you and have them sent to him to install while reassembling. Hoping he has some kits stashed on a shelf somewhere.

dvandentop

damn sounds pretty brutal. if you cant find a rebuild kit it might be best to just buy some used z06 calipers

Dirty Howie

Those rotors do not look bad at all to me. That is minor spider cracks from some to the drilled holes .......


DH

CorvetteZ51Racer

That's what I was thinking at first. I tried to take a picture where you could see how far down in the holes the cracks propagated (which is pretty far, and it's all the way around the rotor, not just at a few), but couldn't get it to come out. For the cost of a new set of rotors, it isn't worth the gamble. Stock Z06 rotors have gotten so cheap they're almost throw-aways at this point.

Joe_Planet

your best bet at this point is probably to get one of those brake cooling duct kits, relatively inexpensive (considering the price of other things) and they should expand the life of your brakes (and other things). If you run the brakes this hot you're going to also toast the hubs soon. I think DRM also offers different pistons for the calipers that hold heat at bay longer.

CorvetteZ51Racer

Yes, I had a set of cooling ducts sitting in the garage and hadn't gotten around to installing them yet. Needless to say, that's changed. I have also checked into the stainless pistons from DRM and am planning on getting a set here shortly.

Just to emphasize, the rediculous amount of heat generated was due to the Active Handling staying engaged during the session. When I've been able to get the AH off, the brakes got no where near as hot.

gkmccready

That's kind of weird, actually. When I forgot to turn off AH for a couple of laps one session I noticed the rear brakes took a real beating. I have never noticed AH on the front brakes... but I've never run a full session or day fighting with it, either.

Dirty Howie

I have gone thru about 3 sets of stock rotors since 4/2008 with at least 10 track days per year .... a set of OEM tires, a set of R6, a set of MPSC and a current set of NT05 with 5 track days. These little crack show up but do not seem to get much bigger. I wait till the rotor is pretty grooved up with a nice lip on the edge so I know its getting thinner then I change.

Just tried a set of DBA4000 and my caliper pins are hitting the rotor face. Trying to find out if its the rotor or my caliper or hubs going bad.
http://forums.corvetteforum.com/auto...ing-rotor.html

Just bought a new set of OEM at $78 each


DH

*C7*

I don't see how AH could have caused this. If AH was to brake one front wheel with enough froce to cause this much heat it seems to me the car would pull violently out of control.

I did not think AH would brake both fronts at the same time to slow the car.

Is it possible AH would pulse one of the rears to straighten the car and brake both fronts to slow the car??

Just trying to understand how AH could be braking the fronts so hard..

CorvetteZ51Racer

When AH is enabled and senses the car sliding, yawing or doing anything that it "shouldn't" so, it will use any combination of cutting throttle body position and pulsing any one of the brakes that it feels it needs to in order to straighten the car out. On a 2.4 mile 17 turn road course without much for straights, that means that, especially on worn down R-compounds, the car is sliding a fair bit and the AH is going nuts.

There is a general belief that AH only pulses the rears, which is true when the excessive yaw rate is generated by throttle-induced oversteer. In understeer or four-wheel drift conditions, it may use any combination of things. What exacerbates the problem is when the driver feels the car starting to get out of shape and begins to correct at the same time the car is, thus the driver and AH are trying to do similar things simultaneously, thus overcorrecting and making both work harder. That's why I like to turn all of the nannies off. I have never had an off in my life when the nannies were off. I've gotten out of shape, sure, but managed to corral it. The only session I've ever run with them stuck on, I have an off which is starting to total up to $2500 worth of repairs (my tires got wiped out sliding over something in the infield, so tack 1 new set of Hoosiers onto the brake repair bill).

I was 20 minutes into the session when this failure occurred. Also, keep in mind that the ambient temperature was 102 degrees, with track temps around 130.