Z06Vette.com - Corvette Z06 Forum

WhosUrDaddy · 07-13-2006, 09:07 AM

This car has seen six track days - 3 at VIR Full; 2 at Summit Point. Four of these days followed the installation of Carbotech XP10's.

Over this period of time I've noticed three things of note:
1) The rotors cracked easier and more severely than I guessed.
2) The XP10's were disappointing compared to my experience with them on my C5 Z06. I found them grabby, difficult to modulate and even worse - they "smeared" pad material too thickly across the face of the rotor. This last element caused pedal vibration and I'm betting increased pad wear.
3) I am disapointed at the above two issues after just six track days. I know my Porsche compatriots have found a way to make braking systems work better for a longer period of time on the track. The General should know how to do this as well.

Below is an image regarding the above.

Has anyone come across better OE rotor/pad options and achieved better results? I'm only a part-time track guy who'd like to do about 10-days per year. So going to aftermarket braking systems is not an option in my mind.

Duke 1 · 07-13-2006, 09:28 AM

The cracks look pretty typical for a cross-drilled rotor, my GT3 rotors are doing the same thing. I would suggest going to a slotted rotor rather than cross-drilled to avoid the issue in the future.

**panzer** · 07-13-2006, 10:38 AM

Consider getting slotted and dimpled. They cut the dimplee to the maximum depth of the rated wear for the disk. When you wear them to the point the dimples disappear it is time to get new rotors. Dimples look almost as good at the holes but do not create the focus point for the cut points to crack from.

GR8 WHITE · 07-13-2006, 12:14 PM

Hows this for a cracked rotor? 12 laps at Hockenheim!

http://smg.photobucket.com/albums/v3...nch =imgAnch1

Velocity · 07-13-2006, 10:05 PM

WhosUr,
I had the same issue... among others, with the stock setup. I have since put on a StopTech brake kit. To avoid future issues.

TAILWAG · 07-14-2006, 03:36 AM

Quote:

Originally Posted by GR8 WHITE

Hows this for a cracked rotor? 12 laps at Hockenheim!

http://smg.photobucket.com/albums/v3...nch =imgAnch1

- duct tape or superglue - that should do the trick!!

gonzalezfj · 07-14-2006, 07:09 AM

Quote:

Originally Posted by WhosUrDaddy

This car has seen six track days - 3 at VIR Full; 2 at Summit Point. Four of these days followed the installation of Carbotech XP10's.

Over this period of time I've noticed three things of note:
1) The rotors cracked easier and more severely than I guessed.
2) The XP10's were disappointing compared to my experience with them on my C5 Z06. I found them grabby, difficult to modulate and even worse - they "smeared" pad material too thickly across the face of the rotor. This last element caused pedal vibration and I'm betting increased pad wear.
3) I am disapointed at the above two issues after just six track days. I know my Porsche compatriots have found a way to make braking systems work better for a longer period of time on the track. The General should know how to do this as well.

Below is an image regarding the above.

Has anyone come across better OE rotor/pad options and achieved better results? I'm only a part-time track guy who'd like to do about 10-days per year. So going to aftermarket braking systems is not an option in my mind.

That failure is typical of "drilled" rotors. I put "drilled" in quotes because in the C6Z the holes are actually cast in. Cracks like you show happen in Porsches all the time.

I have a matching set of cracked rotors from my track days at Pocono.

Regarding your complaints about the XP10 pads, use XP12s. They are a much better pad (higher temp) with more progressive friction and no excessive initial bite. You will like them better than the XP10s for just a few bucks more.

So far I have not found reasonably-priced undrilled rotors on the market. As soon as I find a supplier, I will be buying them. Gary Hoffman has a two piece floating rotor with aluminum hat that looks pretty good, but is about $375 per corner. The rotor portion itself (the part you replace) is over $200 per corner. A bit too salty for my taste.

Other manufacturers offer rotors (Brembo, Stoptech, etc.), but they are even pricier.

Don't forget that you are going cosiderably faster in your C6Z than your C5Z, so more brake heat is unavoidable.

What we need are good NAPA rotors for $25 each.

Frank Gonzalez

Doc V. · 07-15-2006, 07:22 AM

Porsche relies on the following assessment of brake disc wear: "brake discs have to be replaced (as a precaution) [if the] length of perforation hole cracks is more than 5 mm (this means that no service life reserves remain if brakes continue to be subjected to severe loads) and/or if cracks appear at the edge of the brake disc (reduction of braking comfort and of breaking strength)."

jjwvette · 07-15-2006, 07:27 AM

Quote:

Originally Posted by panzer

Consider getting slotted and dimpled. They cut the dimplee to the maximum depth of the rated wear for the disk. When you wear them to the point the dimples disappear it is time to get new rotors. Dimples look almost as good at the holes but do not create the focus point for the cut points to crack from.

I agree

c4c5specialist · 07-17-2006, 11:02 AM

HI there,
Per GM TSB, the following inspection procedure is for all J55 equipped Corvette.

The pass criteria for thermal fatigue testing specifies that the rotor is allowed to have small thermal cracking up to 2/3 of the brake plate surface. The brake plate surface for the front rotor is 50 mm (1.96 in) radially which means cracks are permitted up to 33 mm (1.29 in) radially across the rotor brake face in length. This would be the pass criteria for the end of severe testing. To have a large safety margin, a rule of thumb -- "small" thermal cracks are allowable and the rotor does not need to be replaced unless the cracks connect from hole to hole or the crack reaches the OD of the rotor.

Allthebest, c4c5