I'll try to make a long story short as I know this had been discussed in other threads. Picked up my new ZR1 on Oct 29 and as soon as I got up to 75 the steering wheel began to vibrate. It continued unchanged all the way back to N. Ky (about 200 miles) so my theory of possible flat spotting from sitting was out. I then took the car straight to the only person on this earth I feel good about working on my corvette, Danny Popp at McKluskey Chev in Cincinatti OH. Pulled wheels and all balanced 0 on Hunter balancer. Then road forced them and FR was a 22 and FL was 12. After indexing and rotating tire on rim we got FR to 20 and FL to 10. Drove car and vibration was unchanged. GM sent new FR tire and I bought new FL on my own dime. Got new FR to a 3 (very low) and FL to a 7. Drove car and vibration unchanged. Unhappy, scratched head, went back to Danny. Pulled rotors and stuck them on balancer and they were out 1.5 oz!! (with visible lateral runout) Pulled a 3 yr old 15 inch Stopthech off Dannys race car for reference and they balanced 0 with no lateral runout. We then balanced my carbon rotors by inserting bolts from the inside out and then threading on nuts from the outside with a set of long pliers. Put them back on car and took it out and OMG for the first time since owning the car the highway ride was dead smooth. So happy I want back and hugged Danny. Mystery solved. Now for the permanent fix which obviously should be new (balanced) rotors and should only be a phone call away for a new 120 k vibrating car. (or even a vibrating cobalt for that matter) GMs first reply was that they know about the problem and the fix is to counterbalance the assembly by adding 1.5 to the wheels and indexing them so if removed they could be placed back in same location. Bull$&@#! Danny had to work his way up the food chain until he got to talk to a brake engineer who basically admitted that they had run out of the supply of "Validated" ie balanced rotors and at some point had begun to put on nonvalidated rotors but that he would immediately send me out a set of validated and balanced rotors which he did. Now I have mine and I am happy, but I hate to think about how many man hours are spent out there by customers like myself who are taking time off figuring this out and getting it fixed while GM knows about the issue and is still putting these S#%t rotors on their flagship car. I have lost serious loyalty and faith in GM on this one. They need to come clean now and do a recall on these rotors.
If this is true (and I certainly have no reason to doubt you), that is pretty pathetic on GMs part. I'm glad you got it fixed. I know from their side, it's all about saving a few bucks, but damn, for 120K car you'd expect a little more.
For what its worth, I realize that not all the carbon rotors out there are out of balance. I have a good friend in TX who recently bought a new 2010 and it is dead smooth. I really think from following this that it is mostly in the more recent builds, particularly 2011s or whenever they ran out of what they call "validated" rotors. But, if you have one that is affected you will definitely know it when you get to 75 mph.
This is typical GM. Glad it worked out for you, but think about it. Their top car....who made that decision to pump out crap??? Do they read these forums?? They are losing more loyalists than they know....
I'm with ya Clay. I've written about my problems with the same issue on this forum and Chevrolet says problem solved by putting weights on the "wheel" to fix the out of balance rotors! Bullsh-t! It's not a fix, it's a band-aid. Chevy needs to recall all out of balance rotors, now!
Everyone who has this problem and those who feel Chevy has covered this up and not admit there's a problem needs to call, write and raise hell with GM until they fix this problem and all are satisfied.
It's terrific that you were able to work with a great mechanic and force GM to take care of this. It's also unfortunate that they won't do the right thing and issue a recall.
I'm interested that you believe that the 2011's are more likely to have the problem. Fortunately, my 2011 is vibration free. I bought it on September 29th but it arrived at the dealership about 3 weeks earlier. That probably puts the build date 6 to 8 weeks before yours. As there were most likely not that many 2011 ZR1's built by the time you took delivery, my guess is that the bad rotors are installed randomly and I just was lucky with mine. It would seem logical to expect that this is most likely the case in 2010 as well. That makes a recall more expensive for GM because the problem is not traceable to a specific range of VIN's. However, that is no excuse and GM should still stand its customers. Otherwise, it will be Government Motors all over again - but worse!! Just a theory...not an alibi!!
Harmonics will decide what speed it creates vibration.Glad I didn't have this problem.
That's why you do have a latent problem, all of them will do it when the natural resonant frequency gets excited and amplified. Wheel/rotor balance is not the only source component to stimulate the frequency. Balancing, road force etc are fixes that can help in combination by minimizing the exciting sources one by one. If this was a disease, it is being treated by stopping its spread but the virus remains. If a specific instance of an out of balance rotor is identified, then by all means GM should replace it on a case by case basis. But clearly, the hysteria behind calling for a recall introduces the potential for creating shimmy problems where they don't exist. GM has been through this before, and I expect they will address the problem for those who are experiencing it, as they always have.
Range96, the only pics I have are on my phone, I will try to get them on here. The vents in the rotor start small and increase in size as they go out which allows a bolt to be inserted inside the vane from the inside out and nuts can still be threaded on by reaching inside the rotor from the outside with long needle nosed pliers. When looking at the rotors from the outside you cannot tell they are in there. I would not rec this as a fix, it was only used to confirm the diagnosis.
As for the people to contact, I would refer to Danny Popp at McKluskey Chev 513-679-9470 as I don't know all the people he contacted to get it done. He did say it took a total of about 3 hours on phone time to get it all done.
As for speed and balance it is all about physics and harmonics. Go pull the wheel weights off your wheel and tell me if you feel it at all speeds, you won't. You won't notice it pulling out of your driveway or neighborhood but you will when you get up to highway speeds.