davidk72008

Hey guys,

I have an odd request. My best friend has a 2009 JBM Z06 with the ZR1 carbon slitters/spoiler package, and I am wanting to do something a little different for his best man gift for my wedding. I am already setting up a professional photo shoot for his car and mine, but I thought of something that might be a cool idea if I can get some help.

I need a ZR1 or carbon Z06 used rotor that someone is taking off, or has taken off, their car. I have no experience with carbon brakes really, but do they still look decent overall if they're chipped or something causing the need for a replacement? My plan is to make a clock out of it for him, and in the middle put a plate with the Z06 logo on it. I'll see if I can get the plate painted JBM, but if not I'll figure out something that looks good. Are these bad used rotors worth anything, or could I just pay someone shipping to ship one to me?

Thanks in advance for any help or advice on whether this is possible.

k24556

by the time you get someone to ship you a rotor and you go to all the work, and your buddy finds out it takes more than a thumb tack to hold it on a wall, how about this clock, shipped and with a licensed Z06 logo, and supporting the NCM?:

http://store.corvettemuseum.com/detail.aspx?ID=4502

It has been done, many times with regular rotors just do an internet search for brake rotor clocks.

davidk72008

Ehh, it's a nice clock, but a custom made piece will mean more than a bought clock. We can handle getting it to mount somewhere. It'll be a fun project for me anyways.

froggy47

See if you can connect with someone from the c7r race team.

Sounds like a fine idea.

Good luck.

davidk72008

That would be awesome. Anyone have any idea of how I could contact them?

onargaroberts

I'm pretty sure the factory race cars use steel brakes. I think class rules mandate this.

davidk72008

I think I remember reading that as well. Bump this up. Anyone have some old brakes?

tytek

There is minimum weight (mass) requirement for CCM rotors. Various people on the site use these rotors on their race/track cars. Once they get below required mass, they are worthless and have to be replaced.

Check out a thread on carbon ceramic rotors and you will find a few users in there who may have old ones to get rid of.

tytek

Look in here:

https://www.corvetteforum.com/forums/autocrossing-and-roadracing/3540503-replace-the-zr1-rotors-pads.html

froggy47

So do you have to pull the rotors off every pad change and weigh them?

Do they get a lip like iron rotors?

Do they ever crack like iron rotors?

jvp

They evaporate from the inside out, which is why weighing them is so important.

froggy47

I guess I need to study up on how this all works, I don't really understand. Any links?

Werks

It's really not as complicated as it might seem. They are just rotors made out of ceramic and chopped up carbon strands that are harder than heck. You just put them on your car and run them. You do not have issues with cracking, warping or any of the other stuff that you have to deal with regularly when running iron rotors. After wearing out about 5x pads just pull the complete rotor and hat, take a look at the hat and engraved on it will be Min Weight: 5xxx Grams. The carbon fibers in the carbon ceramic matrix that the rotor is made of oxidize and turn to dust when exposed to temperatures over 700C which is why the rotors loose weight. So just blow off the rotor and then wash it off with plain water (to remove any dust in the vanes etc), allow to dry and then put it on a scale and weight the rotor assembly. If it is above min weight, keep on using it. If it's not, then replace it.

froggy47

Just out of curiosity/interest what happens if you keep running them under weight? I'm sure someone is going to do it.

jvp

They'll lose their thermal capacity (think: mass == thermal capacity) and heat up more quickly than normal. That heat will have to go somewhere and that means back into the pads and into the brake hydraulics.

froggy47

Got it. Thanks!

jvp

To belabor the point, because I'm good at doing that:

Most folks think the rotors have only 1 job, but in actuality: it's 2. The first is the obvious: provide a surface for the calipers to apply opposing torque to the spinning axles. In other words: stop the car!

The second is a bit more insidious when not properly accounted for, and that's cooling. The heat generated by the friction between pad and rotor has to go somewhere. Having it go back into the pad, then the caliper, then the pistons, and finally into the hydraulic fluid is the wrong direction for hopefully obvious reasons. Instead, it should go into the rotor. Specifically: the rotor should first absorb the heat, and then vent it off into the environment.

Mass helps rotors absorb more heat. The more mass, the better. But this mass is rotational and unsprung, which serves no good purpose for the car otherwise. Ideally, you find the lightest material with the appropriate thermal capacity to make a rotor out of.

Remember the failure of the Red Devil brake company? They spent ... who knows how much ... developing, tooling, and building titanium rotors. What a great idea! They weigh nearly nothing, literally (I actually held a large one, and it literally felt like air). But, a small problem: Ti is a superb heat shield. It doesn't absorb heat at all. So what happened with them? Simple: all of the heat generated by the pad-rotor friction was absorbed by the pads because it sure as hell wasn't going into the rotor. Bad juju.

Thus the carbon ceramics. They have infinitely less mass than the iron rotors of the same size, and significantly more thermal capacity in comparison. They don't ablate like iron rotors do, so you don't see cracks, lips, or any of the other usual deformities we're used to with irons. What they do is evaporate from the inside out. As the air is moving through the inside of the vents, it carries away particles of the rotor (likely in the form of smoke).

The interesting bit, as we're discussing here, is: how many different ways are there to make the CC rotors? And which way is better? What defines better? Longer lasting, more thermal capacity for a shorter period of time, less cost, or some combination therein? And who will be the ultimate producer of those rotors?

LateBreak

I've got some used rotors but they're all steel C5's....

froggy47

Not belabored at all, more info = better. Thanks.

Werks

And to add on to what JVP mentioned, the key to reducing wear on carbon ceramic rotors is keeping their operating temperature under 700 C as this is this is temp that the carbon fibers start oxidizing (turning to dust) so as has been mentioned that is how a CCM rotors "wears", there is no loss in disk thickness as is normal with iron rotors because the CCM material is so hard. That also changes the way that the brake pads have to function. Traditionally braking torque is caused in a large part by abrasive friction, basically the brake pad being pushed against the rotor, biting into it and causing friction and wearing both the rotor and pad surface. Almost like rubbing a piece of sandpaper against wood, it bites into the material and abrades the surface which is why you got grooves worn into rotors etc. The more aggressive the pad compound i.e. higher friction racing pads, the more aggressive the rotor wear.

Because the CCM rotor is so hard there is little if any abrasive friction, the pad will simply slide against the rotor surface. In testing a lot of pads the last year or so I have found that pads that work well with CCM rotors seem to rely predominately on adhesive friction or basically they deposit a significant layer of pad material (transfer layer) on the rotor surface and then the pad bites against that transfer layer. Similar to say trying to rub 2 pieces of rubber together generates adhesive friction, they stick to each other. So there are also some fundamental differences in how the brake pads work with CCM rotors versus Iron and that right now is imho the area that we are lacking in, a wide pad selection which is why I've been testing a whole lot of different pads the last year trying to find an ideal set up.