BAD-Z06

2 Piece Rotors Warped – Why? Help Needed


So I decided to upgrade by brakes with ZIP Corvette 2 Piece Rotors with aluminum hat.

I have been to 2 previous events, and am still new to HPDE, but LOVING it!!! I put on Carbotech XP-10s and XP8’s per the recommendation of Carbotech with stock rotors for my first 2 events without any problems in middle of summer. Stock 2008 Z06 and stock rotors. No mods.

Last Event was October and temperature never got above 50 degrees at VIR. I put on new 2 piece rotors from ZIP corvette, and new front brake duct from LG Motorsports. I also purchased another set of pads per request of ZIP since the rotors were new also. Old pads were still fine and looked barely used compared to new ones.

I went out to bed the brakes in during the first session HPDE at VIR, per Carbotech online protocol. The brakes did not feel smooth and pulsed, but I continued to follow the protocol, assuming that there were some inconsistencies in the pads/rotors that needed to be broken in. Wasted the first 2 sessions since it was raining, and wasted the 3rd session bedding in the pads. Did my cool down lap and cool down through the paddock areas as well. Re-torqued everything, but it was in spec.

Took the car out for final session, but brakes felt WORSE than ever. Changed them out after only 3 laps since it didn’t feel safe. Wasted last session as well.

After speaking with ZIP (I will discuss my experience/customer service later in detail as still up in the air), I took them there. They tested them and were indeed warped. They said they were warped because I got them too hot.

Called around and was told that if they were warped to begin with, that will over heat them as well causing them to worsen and overheat even more.

Thoughts? Were they warped to begin with or should I have done something different with the car?

Thanks for the help

Bill Dearborn

I doubt they are warped now or when you received them. Sounds like you have uneven pad deposits on them which can cause changes in the rotor surface resulting in spots with different friction characteristics.


Check out this Technical Paper on the StopTech web site:


http://www.stoptech.com/technical-su...nd-other-myths


Bill

BAD-Z06

I actually drove them back to ZIP corvette. They put them on the machine and said they are warped.

63Corvette

I concur

Adam@Amp'dAutosport.com

I also purchased another set of pads per request of ZIP since the rotors were new also.

They requested you buy new pads because you have new rotors makes no sense. If you have plenty of pad left you don't need pads. Yes, a back up set is a good idea.

Did you try putting your old stock rotors back on and run them with the pads?

Carbotech makes pre bed pads for future reference.

Who made the rotors for ZIP?

BAD-Z06

I did put the stock pads and rotors back on for daily driving. I didn't want to use the expensive stuff while on the street. No issues back with the original equipment. Everything nice and smooth now.

Coleman makes the rings, but not sure who makes the aluminum center piece.

I was told that if the center piece is not torqued correctly, in the correct order, this can cause them to warp when heated up.

I'll keep everyone updated on what ZIP decides to do, whether they will replace them.

80atez

Did you bed them in in the rain?

Seems unlikely you overheated brakes in 50F heat. I have about the same carbotechs and I don't think my tires would ever keep up with my brakes at that temp.

I do think Hib is probably right, but if you started with new pads and rotors, then it seems possible that the hat bolts were way off.. Could also be a caliper issue - like a sticking caliper heating up one rotor for example.

Brakes are kind of a beatch. I have had better luck on my second set of rings than my first.

If you trust the guy who says the rotor is warped, then I'd say it was most likely rapid cooling from rain water or cold ambient temps during bed in.

If it was really wet those ducts may have even been the culprit spraying the rotors with cold water.. Just conjecture, but one thing I know is the law of unintended consequences takes no holidays!

BAD-Z06

Thanks for the reply!!

It was actually both rotors that were warped or had "run out" according to ZIP Corvette.

It had finished raining and was dry before I went out. Being new to HPDE, I didn't want to take any extra risks on a wet (or even damp) track.

The rotors were clearly overheated for some reason. They were blue and even already had some small cracks in them. They were both identical. If one of them were blue and cracked, then possibly a stuck caliper, but they were both identical.

I am leaning toward the hat being not torqued correctly and off alignment. I am just guessing since I don't know too much about this, but if they were off balanced, would that lead to rubbing half way during the turn of the rotor and not being able to ever get cool?

I am not sure.

Thanks!!

Bill Dearborn

I have been torquing wheels on cars for a long time. A long time ago it might have been possible to warp a rotor by improper torquing of the lug nuts as the rotor was mounted on a spindle with a wheel bearing and the lug studs were part of the rotor. Thus the lug nuts were pulling on portions of the rotor when they were tightened.

However, with more modern designs where the hub is sealed and includes a rotor/wheel mounting flange all you are doing is clamping the rotor between the hub flange and the wheel. I am not sure that causes much warping of rotors just due to the design.

Bill

BAD-Z06

On the 2 piece rotors, there is an aluminum hat bolted with approximately 20 smaller bolts to the rotor rings. I was concerned about those being improperly torqued or incorrect order. I am sure that there is some order that I am not familiar with. They came already torqued and bolted together.

When I torqued the wheels, I do the crossing technique and also go from 80-->90-->100 lbs.

Thanks

Zip Corvettes

First off, sorry I was not there Monday, I know we talked Thursday or Friday. I was out sick Monday and Tuesday, when I got back I was on the dyno for the rest of the week. I forgot all about you coming in when I got back until JT said something Friday morning when I was leaving back to the dyno. I did look at the rotor but did not do anything with them yet. I did notice how hot they had gotten which is alarming for the very little amount of time you said they had on them. I will get a better look Monday though. However let me say this, I doubt it is a torque issue. Each rotor is done one at a time and by hand, not with air tools. The bolts are only torqued to 11 ft/lbs of torque and they are NAS bolts. I believe the break away on them is 8500 lbs per bolt. I did notice a couple of things, First this is a ZO6, I am not sure how fast you were running but that could be an issue at some point. You are running our light weight rotor, which is at one time all we offered when we first came out with them. What we noticed with that though was that ZO6 that were not running cooling ducts were able to create enough heat in the rotors to cause damage. I have never had any warp but they were getting larger heat checking in them than what we were comfortable with and in some cases actually cracking rotors. We came out with a floating rotor with a HD rotor, (thanks to Steve Landstra). These rotors have a .100 thicker friction area on each side of the rotor equal to the Brembo. The issue with the Z is that the speeds are increased and the brake cooling is not adequate for the rotors. This is only a front rotor issue, you will likely never see a heat issue in rear rotors. With adequate cooling though you should never have an issue with the light weight rotor. It took us years to actually come out and start selling these to the public, we tested for years on just race cars and our street/autocross car before that. We had several SCCA/TCC prepared cars that we ran these on. Craig Gelston's car ran these all season with out having to replace these which became the norm on all the race cars. Performance AFX and I are partners on these, and the ones on his car get replaced every couple of years. These were on my race car now owned by Tom Guilante and he has been out several times on them. I am interested in finding any problems with them if they exist, but I can't guarentee them against any cooling issues. I would be interested in seeing the car they are on and what brake cooling modifications have been done on it.
Justin

Zip Corvettes

Craig Gelston's car was built by Tony Fegley who we initially were testing with. I met Tony at VIR for a double points race to test the first set of prototype rotors which came off my 00 C5 and were drilled. These were 14" rotors with AP calipers, the same rotor we use on the Z. That car went two races, four warm up sessions and two qualifing sessions on those rotors without any issues and they were the same as yours but drilled. It is not a rotor or design issue with them.
I don't think they could have been warped because the rotor is not delivered as cast, they are machined and both of those rotors would have to have been crooked on the lathe for them to be "warped". Like I said I will look into it some more, but I would also like to see the car. The pads should not have been an issue and you should always install new pads with rotor. If the pads or old rotors are grooved in any way it will destroy the new rotors.

BAD-Z06

Justin,

I was actually hoping to show you the car. After leaving 4 phone calls and emails, I drove 4 hours in the pouring rain to be there to meet you, as you requested. As one of your employees said "You drove the Z here in this weather?"

The car actually has the aluminum brake duct cooling from LG Motorsports. I also have never had any problems or warping with the stock rotors after 2 full HPDE events.

I not yet have gotten any phone calls or a response from you other than on a public forum.

I will be sure to keep everyone updated on the different Corvette/LS forums with the final outcome how ZIP Corvette decides to handle their customer care.

Zip Corvettes

I said I was sorry for not being there on Monday or Tuesday. I was out of the shop Wed through Thurs and most of the day Friday on the dyno with a customer who had a schedule long before you. I am very hard to get ahold of, I do not sit behind a desk, but my voice mail leaves very clear instructions on how to get in touch with me. We are going to figure out what the issue is with the rotors, but if it was not a cause of the rotors, you will be responsible for replacing the rings on them. Just because you are putting this out on a forum does not mean we are just going to replace them. We stand behind our parts, and if our part was an issue we will fix it. If it was an issue with cooling, then it will be an expensive lesson on brake cooling and you will not be the first person with a street car to learn it. The LG ducts are great, but they are only one end of the cooling. Where was the fresh air coming in it at? If you are using the factory front ducts, you are not getting enough air moving to keep the light weigh rotors cool. If you noticed the rotors seemed warped to start with you should not have run them to begin with. The ZO6 does not have floating calipers and this would be a huge issue. I'm just going to say right now it is very unlikely that these were warped to begin with since they are turned down to there deminsions. I have already talked to my machinest on the way home from work Friday night and he will be talking to Colman to find out how likely this issue could be. Again, my gut feeling is cooling, but well see. I have run the rotor into the ground at VIR with no issues. Our 00 C5 ran the same drilled rotors that were on Fegley's race car a full weekend HPDE with no issue and not counting how many miles were on that car. I sold that car in 2006 and the same set of rotor were still on it earlier this year when we changed the oil in car for the customer. This is not something that is made in China and we just flew by the seat of our pants on. We probably have more personal time on these than any other manufacture. Just for information though, your stock rotor has more mass than what the two piece rotor does, they are over 10lbs lighter than your stock ones and the stock ones can handle inadequate cooling to a certain degree. Now when you cool them properly you will not beat the light weight rotors, if you have the floating race rotors they too will handle inadequate cooling up to about 1000 degrees. Street cars at an HPDE are actually harder on rotors than a race car, your car is running full weight at the speeds most race cars run. The difference is that race cars have adequate brake duct cooling. You also have stabilitrac that can use the individual brake calipers to try and keep your car under control at a race track which can cause massive heat to build up in the rotor which can also lead to a over heated rotor and a failure.
Our goal is to figure what happened, if it was rotor was the cause, like I said earlier we will take car of it. If it was something on you, then we will figure what that was so that you don't have to go through it again.
Also I thought you said you were in VA Beach?
Justin

80atez

I have the AFX HD two piece set so I'm interested in this issue. I run stock cooling and have not had issues with two sets of rotors - they work as expected.

What tires were you running?

I just can't see anything short of R6's burning up two piece rotors at a HPDE at 50F... Maybe I don't know how to threshold brake..

I think we're missing something here and I hope you folks get this sorted out. And when you do, please post a punch line so we all learn something.

I personally would have done the same thing if I felt a vibration when starting out, I'd drive on it more and see what happens. It either gets better and all is fine, or it gets worse and what's done is done. That being said, stuff happens to the best of set-ups on track, so I'm not taking sides. I'm seeing both sides. Peace.

BAD-Z06

I have a stock Z06. Well I did upgrade with the mild2wild switch

I am running the Michelin Pilot Super Sport Tires. I did also upgrade to the LG Motorsports Aluminum brake duct work for the front.

I am not so much worried about new rings since they are only around $400, but I am more concerned about WHY this happened. I am also curious to see how ZIP Corvette responds to one of their customers who spent nearly $2,000.

I'll let you know what is found out and what their response is.

Bill Dearborn

A couple of points from my experience. I went to the AFX/Coleman HD rotors on my Z06 a couple of years ago. At the same time I changed to the Lambert Spindle ducts and modded my stock air ducts to take a 3 inch hose. I used the stock air intakes. Rotors didn't thump but did crack with only two days more use than the stock rotors. I changed my brake cooling inlet to the fog light location, changed my modded stock brake duct to an LG replacement and purchased another set of rings. The second set developed a thumping feel which was caused by internal cracking in the rotor. The cracks appeared in the vanes and separated the vanes from the rotor faces. The outside face was separated from 5 or 6 vanes while the inside face was separated from 2 vanes. Basically, the rotor faces were flopping around as the brakes were being applied. These cracks weren't obvious when the rotors were checked with the wheels on. They were only found after the rotors were removed and inspected while turning them in my hands.


Subsequently, I moved my brake cooling inlets back to the stock location, replaced my front side air dams and went with Wilwood two piece 72 vane rotors made from their G37 compound. So far I have 12 track days on the Wilwoods with a lot of heat checking but they are still on the car and not cracked. It looks like I can get at least another track day out of them. So far they aren't cost effective compared to the stock front rotors but at least they last more than twice as long as the stockers. To be comparable in cost I would have to get about 20 track days on them.


Bill

Zip Corvettes

Bill,
Curious about your issue, did you run any heat indicator compound on the rotors? Cooling is a really big thing especially on the light weight rotor. Coleman makes another rotor that we use for HD application we sell that has a .360 thick face vs. a .250 that the light one has. I believe that Robert @ AFX only uses the .360 on his since about 99% of his sales are on race cars. What mode do you run your car in, I see street cars having issues every so often but it always comes back to the Active Handling. On all out race cars where this has been disconnected the rotors last all season or at least until they are timed out. On a full race car I still would want the HD rotor unless there is allot of cooling. I personally don't like the stock locations on the brake inlets, I like the fog light though and you should have had great cooling right there. I run a 3" duct on our setups. Johhny Miller the Trans Am driver was with us with his T1 car at VIR when Landstra cracked a rotor. He also thought is was a cooling issue coupled with Active handling. He was explaining that on the TA car they ran Coleman 12" rotors but had 3 4" duct going to each rotor or cooling. I think all or most of the issues lead back to the cooling of the rotor and it may be why none of the race cars have any issues with them.

Zip Corvettes

I have looked at them and tested runout on them. I will send you the pictures and video. I need to bring in my small digital torque wrench from home so I can check the torque to see what they are. I can tell yo that my normal torque wrench unbolted one with ease but it does not read below 16 ft/lbs. Usually an overtorqued bolt will snap when the rotor gets hot before it warps a rotor. As far as what we do, we always do the right thing, just because you spent $2000 dollars does not mean we are just going to give you parts, it has zero weight in my decision. If you were negligent than you are responsible, I will always help someone who is honest and open about what happened. If we are responsible than we will replace them even if you only spent $5 with us. It is really that simple.
Justin

BAD-Z06

I was told by J.T. last week they were being sent out to Coleman and you were waiting for a response. That is awesome that you got them back already. What did they say? Can you please call me and update me with what they said. I have been without them for over a week already.

Were there internal cracks as previously described? I have no doubt they agreed that it was a manufacturing abnormality. Stuff happens!!!