WX3TKO

New to this Forum, first post. I'm really keen on brakes, and even though this thread has gotten a little stale, I wanted to bring some information forward and seek an answer to let everyone know what the straight skinny is. Sorry in advance for the length of this post.

My background is not Corvettes except as an enthusiast--maybe some day I'll own one. A couple of things to pass along, however.

The information divulged in this thread so far seems to be accurate. The J55 HD brakes (part of C6 Z51 option) list only one rotor for front and one for rear. Front is PN 89060328 and rear is 89060329, rather than 4 separate part numbers like the C5.

Even the standard JL9 brake package for the C6 lists only single PN's front and rear, PN 89060212 and 88955498.

Some in this thread have commented about "just installing regular (or C5) rotors" on your C6 Z51, but that won't work without also changing caliper brackets, at the least. The Z51 rotors are larger in diameter, increased from 12.8" to 13.4" in front, and from 12.0" to 13.0" in the rear compared to standard C6 and C5 rotors. The C6 (and XLR) rotors are improved parts, weighting about 2 pounds more each compared to the equivalent C5 parts, to provide greater mass, thus better thermal characteristics, and incorporate a unique (for the C6) "gooseneck" in the transition from the hub to the rotor surfaces to serve as a heat dam to aid in reducing heat transfer into the hub and warpage problems.

I'm still doing some research, but I am beginning to suspect that the C6 rotors may be a omni- or non-directional part, either supplied by or based upon the design of the DBA (Disc Brakes Australia) 4000 series rotor, as described here:

http://www.dba.com.au/dba_catalogue_...eries_page.pdf

From my own opportunity to look at both a C6 and XLR, on the display stands in front of the Bowling Green Assembly Plant, I too observed the seeming contradiction of cross-drill pattern and position on the vehicle. Not being able to see a rotor with the wheel removed, it was not possible to determine if they are truly an angled-vane design, or something more along the lines of the DBA "Kangaroo Paw" configuration.

I don't know what I'll find, but IF the rotors are actually of this design, while it does not matter which direction the cross-drilled pattern rotates in use, as far as the function of the cross-drilling (Baer does one way, GM does the other, for example), the cosmetics seem a little goofy, and I think GM ought to reconsider this aspect of the Z51 brakes, and add the 2 "correct" parts, or at least offer a TSB to tell customers what the deal is and maybe offer some plain rotors as a preference (and track use) item. At least the rotors "look" the same on the same side.

I presently own a 96 Impala SS that I've upgraded to C5 brakes all around, using a Baer front conversion and my own bracketry for the rear, and have ordered a C6 rear (Z51) rotor to determine if I can further upgrade to the 1" larger diameter. I'm not sure if I can make the Z51 fronts work without a wheel change (to 18's) but the search for better brakes, while staying with OE components, demands that I keep investigating. Once I have the C6 rotor and can get a good look at it, I will report again.

In the time being, while I've not been able to confirm this with certainty, it has been suggested that the C5 can be upgraded to the C6 parts--for regular brakes, all that is needed is C6 rotors. To go to Z51 brakes on the C5 will require the bigger rotors, calper brackets, and larger front wheels. Unfortunately, if you want rotors without cross-drilling, I don't know if any supplier has them avaialble yet in the heavier C6 heat-dam configuration and larger (Z51) diameter.

Thanks for the opportunity to contribute.

Bill Harper
Canton GA
30 years US Navy (Retired)
Chevy guy

kybred

Just a thought, but could the holes negate some of the problem of the rotor spinning backwards and scooping air in because it can escape through the holes and still cool?

sallen619

Same thing on the SL500...

TommyV

I don't buy the centrifugal force theory and like kybred said, they are drilled anyway. Until someone has some hard evidence about one side getting hotter than the other, I wouldn't fret about it.

AU N EGL

For the average street driver it make no difference. PPL who race these cars and brakes it will make a HUGE difference in brake cooling and ware usage.

D/S rotors in most cases are no longer used in competition or any serious track use. The dont last long and crack very quickly. Vein direction is more important. The veins should curve backwards on the top of the rotor as air is pulled in from the center of the hub and ejected from the outted edge of the rotor.

So really there are no worries, just some companies decied to keep costs down by useing only Left or Right rotors on both sides.

joestrus1

I just picked up my C6 with Z51 and noticed that the rotors are larger all around but the calipers in front are larger than the back and the wear on the rotor in the back is about half of the rotor. Do any of you guys know if there is some way to replace the back calipers with something better, simlilar to the front?

BTW: the Z51 rotors will crack if you take the car onto the track from what I hear because of the slots so any good options out there someone can recommend?

Scissors

The rotors on the back are supposed to be smaller and don't need to be any bigger. When you brake weight is shifted forward onto the front wheels. The rear wheels have less weight to stop. Putting bigger brakes on the rears without upgrading the front will result in worse ride and handling.

docrings1

Welcome to the forum! There are hundreds, if not thousands of threads on brakes here. SEARCH and ye shall find... try "brake upgrade" or "replace brakes" etc. in your SEARCH terms...

http://albinoblacksheep.com/flash/posting.php