range96

Were you able to balance it with a single bolt/nut or needed several? With a crush fit nut, this option maybe the best out there.

Reciprocal

No need. When there is an out of balance condition in a sports car, I can feel it at 30 mph, and identify which corner it's coming from. I can feel a drive shaft out of balance as well.

You can too, but you might be programming yourself to recognize wheel shimmy as a balance problem alone. Steering wheel shimmy has other causes, balance is only one of them. Cupping tires, tread patterns, grooved roads, pavement irregularities, anything that excites the resonant frequency. It's not that you can't "feel" imbalance at speeds other than where the harmonic occurs, it's that there might be other sources causing it that you associate with imbalanced wheels/tires.

I suspect the wheel shimmy is the first clue that creates an awareness of a possible wheel/tire imbalance in many minds, but there are other cues to look for, vibrating seats, mirrors, touching panels with your fingers and feeling vibrations and other sensations that can be clues to tire/wheel imbalance that are observable at many other speeds besides 75 mph.

Heck, if you just look at Hunter spin balancers, remember when it used to be called "high speed spin balancers?" They don't spin them very fast at all to sense out of balance wheels, looks like only about 30 mph or less.

RAFTRACER

Dont frequent this particular board on the forum, but I am the Danny that is referred to in this post. I am a certified Corvette Specialist @ McCluskey Chevrolet in Cincinnati , Ohio and have been working on these cars for the dealership for 17 years...

Clay's ZR1 has been problematic for sure, and I and GM completely understand his frustration. Probably not what you would expect from a brand new $120k car. We are not the "selling" dealer of this particular car, but 85-90% of the Corvettes that I work on are not from our dealership, and it doesn't matter as I will give ANY Corvette owner's problem my upmost attention.

Clay's particular problem with vibration is obviously not apparent on every ZR1 or Z06 carbon. I have gone through all of the GM protocol to fix this car properly and GM is interested in fixing his and all Corvette owners problems correctly. They are very aware of current situations more than you know.....they may even know about this particular thread..(ask me how I know ). There are multiple possible causes for cars that exhibit vibrations on the road and isolation of the correct source is paramount. This DOES NOT mean that every ZR1 or Z06 carbon needs new "validated" brake rotors. I am sure there are other cases out there of out of balance rotors, but those will be isolated cases and proper analysis and isolation will be necessary. I have derived a way to check balance on the rotors and balance if necessary if required. This by NO means is a suitable repair, but only a form of diagnosis and confirmation for cars in the field that exhibit this particular concern. New in stock rotors have balance potential from Brembo and in speaking with GM they are deriving a procedure to check and balance rotors for cars that have this problem in the field. They are feverishly working on the protocol for this. This is obviously not a GM manufactured component, they have worked with the supplier to have this not happen from here in the future.

For those of you who have these problems and are frustrated, please contact your dealer and have them address your concerns and involve technical assistance. On that note all dealers are not created equally and every dealer my not have a Corvette only specialist that may be as involved as I. If you are having problems research and try another dealership in the area, or contact me on the previously mentioned daytime work phone # and I will help you (or your Corvette technician) however I can. I have worked on Corvettes from hundereds or thousands of miles away...generally not for warranty repairs, more for race purposes, but.............. . It will be done right at this particular dealership, I guarantee, personally.

Clay's Corvette will be fixed as soon as his schedule allows and GM is eager to make all of its customers happy with their service concerns..Ping me if I can help.

hrspwr

Danny,
Thanks for your input in this difficult problem. I am relieved to hear that GM is working on a solution rather than hoping over time it goes away. I am concerned that on one of the GM service bulletins posted on this forum:
Here's a fairly new bulletin on tire vibration.


#PIC5202A: Tire Vibration At speeds Above 70 MPH - (Jun 18, 2010)


Subject: Tire Vibration at Speeds Above 70 MPH


Models: 2009 - 2011 Chevrolet Corvette




--------------------------------------------------------------------------------

This PI was superseded to update admin details. Please discard PIC5202.


--------------------------------------------------------------------------------

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
Some customers may note a slight vibration in the steering wheel at 72-78 mph. The tires are known to flat spot when parked and this condition may be present until the tires warm up. This condition should clear after 30 minutes of driving.

Recommendation/Instructions:
Drive the car for 30 minutes prior to beginning diagnosis. Check tires for force variation to determine which tire(s) may be contributing to the vibration; 15 lbs is considered acceptable. Rotating tires on the rim, sometimes called match mounting, to get force variation below 12 lbs is helpful.

Rotate the tire/wheel assembly on the hub, one lug at a time and test drive. There can be a stack up of tolerance between the lug nuts and the lugs on the front hub which can contribute to this condition.

If after performing the procedures above, a slight vibration still exists; this is considered a normal characteristic of the vehicle.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.


Reading your post I am glad that you don't consider this a normal characteristic for this car!
Again I am very glad that there are skilled, concerned professionals like yourself who are willing to address this problem and take whatever measures are needed to repair. I wish I lived in the midwest! I am not sure at what point I should take my car in for evaluation, since the more experience the dealers get with this problem may shorten the course of treatment for my car. But again I thank you for your great post.

Reciprocal

Outstanding Danny!
Building and servicing perfect cars is something no one does, but doing it with pride and passion does go into the Corvette.

DebRedZR1

I KNOW they watch these threads I am sure the issue with my ZR1 would have been resolved much faster had it been at the purchasing Dealership who does have a clue as opposed to the local IDEOTS who made things worse. The GM Guys who eventually came to do the fix were AWESOME! Thanks for being one of those who cares

starr1

I'm "with you" on Danny working on your ZR1. He is the only person I let touch my Z06. We are lucky to have him at a local dealership even though I drive 130 miles round trip to Cincinnati.

Kelly100

Those have got to be some after market wheels to take the chance on a perfectly running ZR1. I don't really mean a bash here, but I am always curious as to why people would do such a thing to this car, IMHO. BM ALWAYS creates problems of some sort for their customers, right out of the box. I have learned the hardest of ways not to ask for more. And I know to each his own

range96

Please, let's keep this thread on track for those of us with vested interest in this. We are interested about the fix for unbalanced rotors.

Thanks