slowjunk

Is anyone making aftermarket C6-ZO6 rotors with the correct vane direction for both sides yet? No more backwards GM junk.

Hopefully NAPA or Rock Auto!!

DoingOK

Racing Brake and a few others..............but expect to drop >$750 a pair for the fronts alone.

Solofast

The reason they used the same rotor on each side is that it really doesn't matter much....

One of the key reasons for "sweep" in the vane shape is to avoid distortion, warpage and high stress that would result from a purely "radial" vane shape... To put it another way, if the vanes were purely radial they would create a lot of stress, because the vane would be much cooler than the outer surfaces, and that would lead to warpage. By "sweeping" the vanes they avoid that warpage that would cause pedal pulsation...

At 100 mph the fronts are turning only turning 1360 rpm, (this is a tip speed of about 70 feet/second, or about 1/20 of the speed of good compressor) any mostly radial vane is going to perform pretty much the same at that low a speed. In fact, the "sweep" in the properly turning vane actually lowers the effective tip speed of the rotor and it will tend to pump less air than a purely radial vane. The rotor running backward has a tip incidence issue, but that not that big a deal at this low a speed.

If you want to promote airflow thru the disk (and cool the brakes) you really need to add a set of spindle ducts and ram the air thru the brakes. Relying on the air pumping action of the brakes isn't really going to do it for a car with this much power.

slowjunk

Maybe we should picket the corporate offices of NAPA until they bend to our will and get to making the cheap 1-2 race weekend rotors.

davidfarmer

Solofast, while I agree with you in principle, the car comes with ductwork that is just BEGGING to have spindle ducts (or at least flex hose) added. Regardless of that however, the truly huge mistake is the drilling. Our rotors cracked at Roebling last weekend, and I now happily have RB rotors on the car.

With the properly vaned rotors, I've added ducts and new pads, and anticipate these rotors lasting much longer than the OEM swiss cheesers.

RB has front and rear rotors available, and Stoptech has fronts only. I am a dealer for both. Tire Rack also has 1-pc replacement rotors available, but haven't heared how they hold up yet. Should have lots to look at at the NCM VIR event next week, and we should all compare notes.

davidfarmer

Sorry, while the brakes are indeed expensive, replacement friction rings are about half the initial cost of the complete sets.

95jersey

I have 3 track days on my OEM's with barely any cracks....we shall see, but things look OK at this point.

TeddyFreddy

That is not true. I cannot calculate now how much air is pumped by a rotor, but I say that even if the RPM is low, there is some air pumped from the center of the rotor to the outside.
*** With the wrong direction rotor the air is pumped the other way around, from the outside to the center. That means against the airflow coming from the air duct.
*** false, corrected as per GonzalesFJ

There are cooling reasons why performance brake rotors are not straight-vanes [SRV]:
"The total heat transfer from the SRV-R and DTDP passages is up to 20% greater than that for the SRV rotor"
[ From http://www.ingentaconnect.com/conten...ag39igk7.alice ]

Also a simpler article: http://www.forparts.com/techdir.rotor.htm

GM should be ashamed!

gonzalezfj

The bolded statement above is not true. Pick any good mechanical engineering handbook and you will see centrifugal fans with the vanes pointing forward. The flow of air is ALWAYS from the center to the periphery of the fan.

Forward-facing vanes produce flow vs. backpressure curves that are desirable in certain applications.

All the hullabaloo about "wrong side rotors" is a tempest in a teapot. Rotor temps don't vary that much from "right" to "wrong" side, but many here don't understand the physics involved.

What is wrong with the OEM rotors are the @#$%^& holes. They are there just for bling -- because Porsche, Ferrari et al have them.

As soon as there are decently priced undrilled rotors, I will buy them. I'm not ready to drop $700 for a couple of front rotors.

YMMV,

TeddyFreddy

You are right about the direction of airflow. But the cooling is better with the proper direction rotors.
Backward-curved airfoil impellers provide the highest efficiencies for centrifugal fans.


So you are saying that GM did well providing same direction rotors?

Everybody in the performance brakes industry is wrong and GM is right?



I guess that StopTech got their patent for the AeroRotor design for nothing... http://www.stoptech.com/proven_technology/patents.shtml

gonzalezfj

My point, Teddy, is that the vane direction isn't as big a deal as some have indicated. Now the holes... that's a real problem.

Frank Gonzalez

Notch

Porsche's testing indicates that the holes are not "just for bling". Their tests show that the internal venting lowers the temperature by 36 degrees F, and the holes reduce the temperature by an additional 90 degrees F. The holes also also allow water to evaporate faster.

If a 90 degree temperature decrease is "bling", then I'll be glad to have some of that.

davidfarmer

Porsches holes are CAST into the rotors, not drilled. However as a recent 996 Turbo owner, I can tell you they still crack AND cause uneven pad wear.

Give me a smooth or slotted rotor ANYDAY over a rotor with holes.

Back to the GM rotors, we did have a bunch of us driving the Z06 prior to the rotors cracking, BUT all of the cracks propagate from the holes, and there are no free-standing holes like you see in C5/C6 rotors.

Solofast

You are assuming that aerodynamic pumping efficiency has anything to do with cooling. I does not..

The efficiency that you are referring to is the amount of air pumped at a given pressure ratio, versus the work put into the shaft. That is, how much power does it take to pump the air that goes thru the rotor. More aerodynamic efficiency just means less power is required to pump the air thru the brakes...

But since we are talking about less than 1/4 of a horsepower here, wether it is 1/3 or 1/4 of a horsepower it makes no practical difference.

The key parameter for cooling brakes is cooling flow for a given shaft speed. And backward curvature design (what the normal rotation is) is indeed more efficient, but it doesn't necessarily flow more air. In fact, generally, because of lower tip speed effects, it actually flows less air. A purely radial rotor would flow more than similar backward curved rotor, and potentially a forward curved design could flow even more, but there are a bunch of other issues that go into the design effects, so I don't want to generalize too much here.

Didn't want to be picky, but simply, efficiency has nothing to do with it.

TeddyFreddy

The consensus in the brakes industry seems to be backwards curved vanes (Porsche, StopTech, Brembo). Maybe air travels over a longer path and it cools the rotor better.
I am not a specialist in centrifugal compressors or brakes, I just tried to help based on information I have found.

C6400hp

DBA makes a reasonably priced one piece slotted only for the Z06.
http://www.buybrakes.com/store/DBA-42992SL
http://www.dba.com.au/2006/products_4000.asp

They also make a pricier 2 piece design
http://www.buybrakes.com/store/DBA-52992SR
http://www.dba.com.au/2006/products_5000.asp
I don't have any experience with them but, seems to be nice quality pieces.

They use what they call the "kangaroo paw" design.
http://www.dba.com.au/2006/videoclip.asp

trumper Z06

Thanks for posting the DBA info.

Late last year... when I was looking for Z06 rotors... they only offered the two piece rotors at a much higher price. Glad to see prices are lower... and a wider selection.

I think they are a supplier to the Australian brake mfg'r who supplies GM.

96CollectorSport

FYI
The tire rack also offers the dba rotors, chances are theres a tirerack about a day away from you.

http://www.tirerack.com/brakes/resul...ategory=Rotors

urslooow

Have a few small cracks around the holes after 5 events (3-4 hrs seat time each event--Thanx Chin). I can barely put a fingernail (doesn't sink in) in them and they do not connect to the other holes. But I want to have an extra set of rotors to bring to Sebring in a couple of weeks. I suppose these rotors have to be bedded to my dtc 70 pads

kentz06

After two hard track events I decided to change the front rotors because the cracks were connecting hole to hole. When we took them off it was visually easy to distinguish right from left. The right side had noticeably larger cracks. I realize a one rat study does not absolutely prove the vane direction does makes a difference. Has anyone else noticed larger cracks on a specific side?


Dean

BTW I am trying the two piece Stoptech rotors with stock calipers. After three hard events they have significant surface cracking (checking may be a more accurate description) but no problems to worry about yet.