QUIKAG

Okay, I won't provide specific details on how I got this information so I don't get anyone in trouble. I don't think this is top secret anyway, but just want to be safe.

When GM first requested the carbon ceramic brakes, GM required a tolerance of 90nm (I don't recall the specific measurement, so I'll just use nm). GM then changed it to 30nm and now they have the tolerance requirement to 15nm. This is why Brembo is now using the weights to balance the rotor.

Coolest bit of info is now Brembo very recently developed a technology to balance the rotor using ultrasonic pulses. So, in the next year or so, the rotors will be very, very tightly balanced from the factory without the need to use weights using this new ultrasonic technology to 'clean up the rotor.'

Anyway, pretty cool stuff and just remember not to blame Brembo for the rotor imbalance as Brembo was always within spec of what GM was initially requiring. The rep said GM didn't realize the "looser" tolerance would cause a steering wheel shimmy for some vehicles hence the reason GM kept tightening the tolerance requirement to Brembo.

I've had a slight shimmy in the past on my '10 ZR1, but it seemed smooth itself out after a few track days and a few thousand miles of driving. It also seemed to be somewhat road surface dependent, so I never worried about it. It's fine now.

Glenn Quagmire

Good find! It's nice to put the pieces of the puzzle together!

shaimerej

Thanks for the info. Interesting.

ZR1Cat

Most interesting information. Thanks for sharing it.

DebRedZR1

I know they started changing things after looking at my car
Maybe by the time I have the rotors replaced in the spring the new technology will be in place-thanks for the update and I will add this thread to the sticky

OnPoint

I presume if a fella ever needs to order new/replacement rotors, he get's these new whizbang ones, right?

Allzwell

Most probably also the reson that no one is standing up to fix the issue since the supplier delivered product to spec

Interesting and very very believable

ss2z06

Great to hear. Do you know if GM has a tsb pertaining to this? I wonder if they will be willing to send the rotors to be balanced or replaced with the newer ones under that newer tolerance. I still have a slight vibration but have just been dealing with it for now. I have had it with the dealer multiple times now.

DebRedZR1

I will be checking that one

911/Q45

I wonder if the older low spec ones will show up somewhere at a discount price?

BearZ06

You could try contacting Customer Service, it seems sometimes it helps and sometimes not.

http://forums.corvetteforum.com/memb...-cust-svc.html

timmyZ06

could they balance used one too? So folks with shimmy wheels could have this issue fixed out.

Gary '09 C6

good info...thx for sharing with everyone !

mirage2991

Right, like i have said before, gm cheaped out on the rotors because it cost less to have a part with looser tolerances.
Now they might be closer out of the box but, as they vaporize from the inside out they can go out if tolrence too... after all, i fixed my shimmy by burnishing my new rotors... smooth as glass now.

My suggestion: go burnish or reburnish your brakes and see if that solve the shimmy.

NofakeJake

Oh PLEASE!!!!!!!!!!!

Why would you say something so moronic as "GM cheaped out".

To quote Quikage "Anyway, pretty cool stuff and just remember not to blame Brembo for the rotor imbalance as Brembo was always within spec of what GM was initially requiring. The rep said GM didn't realize the "looser" tolerance would cause a steering wheel shimmy for some vehicles hence the reason GM kept tightening the tolerance requirement to Brembo."


And please tell me where is your proof the 90nm is any cheaper to produce than the 30 or 15 nm example given.

Open mouth and insert foot....

K B Vettin

this is getting good

mirage2991

look where i work then ask yourself if i know a thing or two about manufacturing and cost, along with GD&T tolerances and producibility in cost.... yes tighter tolerances always increase cost. Brembo will charge more for it, period. just like when we design a part with tight location tolerances and size tolerances, the cost will go through the roof.

you don't have to believe me but trust me you'd be surprised.

C5kid

^^^ agreed, you should see some of the tolerances on the fiber optic stuff we do, then you understand why a little part can be a couple grand.

mirage2991

GM thought they could get away with looser tolerances to drive the cost down. No harm done many companies do so to offer a better priced product. Obviously that had some negative effects and they now are tightening it so that less people have a problem right out of the box (the right thing to do).
I do not know nor can guess what that cost increase is...5$...100$... but there is one.
On fastners, if we go oversize beyond the "normal" oversize the cost of one bolt is 250% more...

ss2z06

Thank you, I sent him a pm.