mirage2991

I know, we have 18 pages of sticky, and other links to it, but bottom line, I was out of commission for 2 weeks for this issue and after tires being replaced, TSB being followed, and my tech who genuinely wanted to get the car fixed, simply put: just balance the dang on rotors and enjoy a smooth ride.

My rotors were 1.5 and 0.75 off respectively. There's not TSB that tell the techs to balance the rotors, and my tech refused to give me the car back using the "get out of jail free" statement of the TSB "...this is considered normal".

I showed him some of the threads from this forum and the Aston Martin TSB. He balanced the rotors, use the offset weight of each and now I have a car that rides smooth

Monday morning he will call GM and issue a QA tag against the rotors (can't remember his exact wording but that's how we call it in the airplane biz) and will present the solution to be made into a TSB. Of course, he doesn't know if they will do anything about it, I suppose they can choose to ignore it he said, but at least, we both feel we are doing the best we can to share our knowledge in order to get something fixed.

Moral of the story: if you have the shakes, RF and new tires didn't solve it, talk to your tech, show him all he has to do is balance the rotors.


2756 miles of shakes, today, my first 15 miles of shake free was a total bliss!!

***update***

Unfortunatly, the shake simply moved to a different speed that I could not test "correctly" on my daily commute or around the dealer. After taking a 800+ miles trip to go drive the Tail, I can confirm the shake now starts at 82, is pretty annoying at 85 and seems to stay there above that. It continues to come and go as you take turns.
Tech believe he should have entered the Wheel diameter as opposed to the disc diameter to figure how much weight was needed, and I agree. Looks like I have to much weight added now.
He agreed to change rotors, but GM is holding things up (the GM engineer that supposed to approve "Expensive" parts order I suppose). Almost four weeks and nothing, I call just about everyday and the dealer is still waiting on a response.

Just go off the phone with GM customer service, they are completely useless. I have explained the situation, all they want me to do is bring the car back to the dealer...except I already did that on October 8th so they could get the Vin and mileage on a work order so they could get new rotors. While I was holding they talked to someone other than my service advisor, which I've never delt with...so now my case will be "reviewed" because I'm not taking the car back until I know what this Service Rep wants to do...but unfortunately, no one knows because he is not providing that info to my dealer.
Seriously??? is this so freakin' hard for someone at GM to get a hold of this guy and ask what is the plan of action for my situation...

***Update 2***

Senior Tech called me yesterday am early, stating he was going to go up the ladder with my issue...it worked, as I received a phone call from the Service Director from my dealer. Basically he is requesting an Engineer to come down and take a ride with me. He stated he provided the data (rotor imbalanced by 1.25oz and 0.75oz) yet the engineer still stated some vibration was "normal". I indicated to the Director that a few of us are having the issue and new rotors are the solution, even when others have had GM engineers come down to look at their car. I will play ball...for now.

***Update 3***

Senior Tech called me this am: New rotors have been ordered. As soon as he gets them, he will verify them and if they check out good, he will put them on the car. He apologized for the BS again...this guy rocks, this world could use a few more people like him that genuinely care to help a customer and fix a somewhat complicated problem! I'm pretty positive that it is all his doing too!

***Updated 3.5***

Rotors have arrived...apparantly those are still off by 1/4 and 1/2 respectively. Tech was told by Engineering support that as long as they are at or bellow 1/2 oz it should not matter. He wants to try them, so we scheduled a time for thursday afternoon...

***Update 4***

new rotors were put on, no change. Probably because they to are off... Made a phone call back to my advisor, they'll get with the service director and have an Engineer come down to look at it.
Here's the interesting part: the new rotors, which have those extra taped holes in the hat, is so Brembo can balance them. A new 2013 Z06/Z07 in their showroom had a little weight on the front rotors (both of them). Interestingly enough, mine do not have that weight (and they are off none the less). Even more interesting: no one can find how or where to get those weight. It isn't listed anywhere, which tells me this is an in house Brembo deal.
At any rate, I'm discouraged. I've openly told them if nothing fixes it I'll be looking at GM to buy it back via the Lemon law.

here's the pic of the Z06 rotors and the weight:



**update 5 **

Dealer had the car for a few days, GM engineer came down, they spent time taking measurements and indexing rim, tires, rotors...and what not...I was told the Engineer said it was way better....wrong...it's actually worst....the saga continues...I'm at the end of my rope on this one...

**Update 6 **

98% of the vibration appears to be gone now.
Out of frustration last saturday, I went out to do the burnish procedure with the new rotors (granted I wasn't sure if I had done it properly with the original one). I couldn't drive 75-90 on the way back as the brakes were well, soft from all that heat. For the whole week I avoided the interstate, except a couple time and I noticed the car was dead smooth at 75mph. Yesterday after work I decided to take the interstate and drive out of town where I could check the speed from 72-92.
98% of the shimmy is gone now. The worst would be a light tingle at 82-84 which goes away (seems surface/road crown related) and 80 and bellow is dead smooth.
Called my dealer, baffled, as I have an apt with the district engineer monday, to check it but I now can't reproduce the concern like it used to be (whit knuckle shimmy really).
This isn't over though, the plan is to re-test over the week-end and driving it down to FL for x-mas, this will tell me for sure.

Two things come to mind: my new rotors still had a small imbalance (1/4 and 1/2) so perhaps the burnishing procedure vaporised some of the rotor material, improving the imbalance = this mean it could potentially go in and out over its life time
or
The alignment moved a tad during those super heavy breaking (did a few from 100 to 0 along the 60-0) and perhaps it settle into a position less prone to shimmy.

all guesses...sure as heck nice to have this almost gone...

911/Q45

How did he balance the rotors?

BearZ06

Great question. Was this done at the dealer or were the rotors sent out for balancing? Even then I'd like to know how it was done. Fortunately my car does not have the problem but this solution is good news.

3LZZ06

I assume it was done with offset wheel weights...

DebRedZR1

Thanks for the update JB! Always good to hear a success story

Nanook

I don't have the problem but a local shop I've used in the past have a machine that spins the wheels on the car...uses a magnetic sensor that attaches to the suspension and stobes when the weight hits the bottom. The mechanic then marks the tire with a chalk and proceeds to balance by adding weight opposite the chalk. This balances the complete assembly..tire, rotor, wheel. At start the shimmy is evident by touching the fender but with time he could completely smooth out the inbalance. Of course you would have to index the wheel to the hub location.
Rears were done by spinning the wheel in gear which may present a problem on our cars ...having both rears spinning at the same time...
I have not been back to this garage for years and am not certain if they still have that device or if they are still made but sometimes old methods out perform the newer technologies..

Gary '09 C6

...good to hear a solution was found for your car, and maybe for some others !

Nanook

Here it is..I found a video..
They call it a Hunter strobe balance

http://www.youtube.com/watch?v=tMTFzsfHoUg

And if ya got run-out...gheeze I can't believe this..

http://www.youtube.com/watch?v=0DJib...feature=relmfu

mirage2991

All done at the dealer. Rotor was mounted on the wheel balancing machine and spun on the dynamic setting.
The rotors have the same center hole diameter as the rim, so it is mounted on the balancer just like a wheel would be. No special tool.
Sticky weights are then added to the wheel mirroring the location off the rotor where the imbalance was found.

OnPoint

Glad they solved if for you.

Sounds like your vette tech is a good dude. Nice to hear.

911/Q45

All that will need to be reaccomplished every time you get new tires and you'll need to index your wheels back to the same place every time they are removed.

pcguy2u

I was hoping that someone finally decided to take some weight off the rotors to do the balancing - like on a lathe, or? This is still a bandaid fix.

mirage2991

yup, indexing takes 3 sec with a grey marker: mark the stud, mark the rim, that is a none issue to me.
Since i know where the rotor imbalance is and by how much, when i need new tires in a couple years all i need to do is tell whom ever will replace the tires to not remove those weight and to index the rims. knowing me, i will just bring the rims and tires to the shop. Again, not that big of a deal.

mirage2991

I know what you are thinking about... i figured one could enlarge a few cross drilled holes on the heavy side to remove material... but there's a couple issues just in the attempt to machine this:
you will need a diamond bit, you will need to know the rotating speed at what the bit needs to turn at, and the feed through speed. you also run the risk of blowing the exit side if you do not have a back plate... all this on a 1400 dollar rotor... that's high risk... or you can use 30 cents worth of weights to offset it... or if enough techs call gm with a QA tag maybe we can get GM to issue good rotors... highly doubt it on such low production... but worth the try i think.

pcguy2u

Here's the rub in all this - it's been a known issue for years now. How long does it take to implement quality control on a known defect? Why is GM still accepting and installing rotors that are known to be defective?

pcguy2u

Not sure how that page is really relevant. The issue here is the rotors and the word "rotor" does not appear on that page???

BearZ06

GM should replace ALL unbalanced rotors because they are defective. They need to be returned to the manufacturer. This is another known problem that GM chooses to basically ignore.

GasmanZR1

I agree!! I'm having this same problem....My dealer replaced all of my tires and still have the shakes. Got a call in to my service director about getting new rotors. I had given him the AM fix and he said it was BS and not good for the tires....

isnider

The whole indexing thing is ridiculous for guys who track their cars, are rotating tires side to side, and constantly replacing tires and wheels. When it's finally time for me to replace these rotors I am immediately going to return them for an exchange until they drive without vibration.

I have three sets of wheels and tires and am just not going to accept the problem is anything but the rotors....period!

Ian

3LZZ06

For the guys that track their cars, this problem becomes a royal PITA.

For the guys like me who may rarely or never change wheels, it's not big a problem with identifying the rotor imbalance and compensating with weight on the wheel with an index mark...I agree it's not the right fix, but for most it wouldn't be a big deal.