vettemaster1

also lets not forget that all 4 rotors have cooling ducts forcing air through the brakes.....higher flowing than previous models....the direction of the vanes in the case of the z06 probally makes little difference.....

my.02

TA

That being said I'll still say that I don't think its going to make any difference.

Tom Steele

I dont buy that. They are forcing air TO the brakes, but if you are suggesting that the air is being forced through the holes in the brakes, (and maybe you weren't, I could have misunderstood) then I'm not buying that.

Jim is right about the vanes not pulling air if they aren't drilled. How would they? There is no exit (or entrance - whatever). They are a dead-end. If they were "throwing" the air from the inside to the outside, they would create a low pressure situation in the rotor, and if they were "scooping" air from the outside to the inside they would create a high pressure situation in the center of the rotor. But there would be no airflow without holes in the rotors.

However, I suspect that we are delving into an area which very few people know as much about as they think...

Obviously the people who are supposed to know about it (GM's engineers), didn't think it mattered. And considering the fairly hardcore attitude they took on this car, if it did matter they probably would have addressed it.

On the other hand, holes in the rotors are silly, but they did that anyway...

ffr1352

Go out and do some 70 to 10 mph braking several times rapid succession and then pull off and measure the rotor temperatures on both sides, front and rear and report the results. If the front rotors are about the same temperature and the rear rotors are the same temperature then vane direction doesn't matter!

tkrussell

From the evidence of this thread, Vette owners are highly opinionated, rather intolerant, somewhat biased, and exceptionally prone to take offense.

Most of the folks asking questions, and many of those answering them, are just trying to be helpful in good faith. No need to flame someone unnecessarily.

Baer seems to have it right (centrifugal airflow inside to out with internal vanes sweeping the airflow inside to out). The externally seen slots and drillings are counter to the internal vanes and point in the opposite direction, lending confusion. Source: my 95 Vette w/ eradispeeds.

GM apparently has chosen the cheap way out yet again. Guess Baer will get an order from me on my forthcoming C6 Z06.

vettemaster1

Jim is right about the vanes not pulling air if they aren't drilled. How would they? There is no exit (or entrance - whatever).

the vanes are open to the inside of the rotor as well as the outside...they flow air regardless of the cross drilling....

jvp

No, it doesn't, and it's wrong. Vaned rotors are specifically built TO circulate air. From the hub, outward through the interior of the rotor, towards the rim.

Cross-drilled (or cast-in) holes in the rotor surface are there primarily for pad out-gassing. The concern here is that pads form a pocket of hot gas and don't come into as close contact with the rotors as they should. The holes help the gas from the pads escape into the interior of the rotor.

Now, today's pads don't out-gas anywhere near as much as ones from the past. So cross-drilling (or cast) doesn't help as much as it used to. However, any time you increase surface area, like, say, drilling holes, you help in cooling.

jas

Edit: I see that jschindler is a bit confused as to what we're talking about. The vanes in question go from the hub all the way to the edge of the rotor. In other words, the area between the rotor surfaces is open, and air can move from the hub outwards. The cross-drilled holes have nothing to do with this.

jvp

If you don't take your car to the local road course regularly, you're probably right. It won't make a big difference. To those of us who'd like to use the Z06 for what it was meant, it will. Hot rotors == hot pads == hot fluid. Brake fade and boiled fluid is no fun at the race track.

Been there, done that, got the skid marks.

jas

EuG

I say, don’t sweat it.
Stock cross drilled 1-piece heavy POS will probably crack at the track pretty fast anyway and should be replaced with nice lighter 2-piece solid ones

jschindler

Huh? Us, opinionated, intolerant and somewaht biased...

Okay, I'm good with that!

By the way, since my last post, I see two people have agreed with me, and one has disagreed.

I'm very sincere when I say that I apologize if I was wrong. I still don't know for certain if vented rotors are open on both ends, but I sure didn't think so,

Ego-Trip

This is the best example I can give on short notice. This is a pic of a Baer 2-piece rotor minus the rotor hat.



As you can see, they are definitely vented all the way through, pulling air from the center and forcing it outward. I am assuming that a Z51/Z06 rotor would also be the same but I have nothing to confirm that.

To clarify too...I really dont have much of an opinion on whether it adversely affects performance enough to make a difference. JDogg said something above about there being something like a 7% difference in efficiency so I'll just go with that. My only contention was that I didnt care for the looks.

Yody

Thanks for that picture, I can now see why Baer positions the rotors they way you see them. The vents scallop towards the back, like your hair in the wind, but the holes go foward. Most companies don't do that, they usually match the holes with the vents. I think that pic will also show jschindler how the vents work.

jschindler

I don't think that a picture of an aftermarket brake rotor answers the question. We were referring to factory brake rotors. If a factory rotor looks like that, then we'll have our answer.

Yody

that is what a factory rotor looks like, just the hub is cast into the rotor. Have you ever even taken off of a rotor before?BTW no offense but we don't need the answer, I know what a rotor looks like, and "somewhat" how it works. Picture is for you.

jschindler

First of all, why the attitude? I have said in two separate posts that I apologize if I'm wrong. The reason I asked for a picture is that there is some confusion (two other posts agreed with me), and I just didn't know if an Bear Eradispeed is built like a stock rotor - fact is, there are some major differences. Like the Bear is two piece, and it's drilled.

Now, the reason I actually came back to post is that I have searched for more pictures, and while I couldn't find one that showed both sides, I found some that indicate that I was, in fact, wrong. Therefore, you have my apology, and I stand corrected.

ZO6vettepilot

Exactly. BTW, there are two types of "vented rotors", both provide increased cooling to the rotor. The first type has vanes that are cast radially from the center of the hub to the outer diameter. They provide good cooling characteristics, and X amount of surface area for the metal to air cooling. The second type of vane is cast radially, but is curved. When correctly installed, the curve is to the rear when the vehicle is driven forward. This type of vane is more efficient than the straight vane rotor because the curved vane can create higher velocities therefore they move more air for a given rotational speed. The curved vane also elongates the sectional of the vane, thereby increasing the internal surface area and creating a larger cooling surface for the air to act upon for cooling.
The theory behind all this is, air has mass, mass has weight, the rotor is acting as a centrifugal air pump, moving air from the center of the hub, through the vanes, and exiting around the circumferance of the rotor. Cooling takes place as the air flows through the vanes.
This type rotor is normally referred to as a "vented rotor".
"Non-vented rotors" are solid cast rotors lacking internal vanes.

The cross drilling and slots provide no enhanced cooling characteristics for the rotor, they do provide an escape route for gassing that is produced under extreme braking conditions. They do not increase surface area as somebody eluded to, but exactly the opposite, they decrease the surface area by the total area removed from the rotor surface either by drilling, or the grooves made for the slots.
Cross drilling can promote hot areas around the holes during braking that are prone to producing cracking around the holes, chamfering the holes helps but probably cannot eliminate proness to cracking.
Now I know somebody will ask why Chevy put cross drilled rotors on the Z51 and the new Z06.... you should ask the design team. Maybe they want to increase parts sales, they want to sell rotors?

...and yes you do see cross drilled rotors on track cars, they do work under extreme braking to release the outgassing, but remember those track cars get new rotors almost every time out.

zo6vettepilot

Yody

Very well written post, with lots of good info. Another thing, is that crossdrilled rotors shoudl be lighter than a rotor that isn't crossdrilled. Alos the holes reduce surface area which actually will make the brakes hotter since the rotor now can't absorb and dissapate as much heat. Supposedly they also help in "wet" driving which is why a lot of foreign high end cars use them. I assume they used these rotors for looks and to compete with the european or foreign high end cars that have them

Tom Steele

I always assumed the inside of the rotor was solid. Of course you know what happens when you assume...

Z06 Quin

http://www.baer.com/support/TechTips.aspx?TechTipID=2

KRAYZ308

This post has been the most entertaining. Did I spell entertaining correctly? If the car has directional rotors then the car should have left and right rotors to be correct, period. Even if there is only a 1% difference in cooling.

The reality is that for most owners to drive hard enough to tell a difference in the rotors is only a wet dream. Many would run out of talent and stuff it into the wall first. The rest that track their cars will change to aftermarket brakes because that's how the universe works. You either prepare the car with the uprated parts first, or, you change what breaks with better aftermarket parts and come back next weekend.