G6 Rotor problems and "DTV"
OK, I know brake issues with G6's have been discussed here until people are blue in the face and I'm not trying to drudge up old posts or threads. HOWEVER.... I can't find where this particular take on the brakes has ever been discussed so I'm throwing the red meat out for dissection.
Quick summary - I own a 2006 G6 with 89K miles (wife's car). At 81K miles, 7 months ago right after I purchased the car I did brakes and rotors all the way around as the installed brakes were worn and needed changing. I'd researched the problems on the brakes right after I bought the car and thought I'd do the right thing by getting drilled & slotted performance rotors with high performance pads. The rotors should dissipate heat from brake applications better, no warping problem, etc etc..... I purchased the PowerStop 4-wheel brake kit from Summit Racing, their part #K1612.
Well, after 7,000 miles and 7 months the brakes are pulsing now so badly as to shake the steering wheel and cause the steering shaft to knock with anything other then a feather-light application. My wife drives like Harvey Milquetoast and she's not doing burnouts, drifting, or panic stops every quarter mile. Obviously there's a problem here. I contacted Summit to warranty the rotors (my assumption is they're warped). This is part of the response from PowerStop, attributed to something called "DTV" and NOT warped rotors...
"Many drivers confuse rotor warping, or warped rotors, with a condition called DTV (disc thickness variation). DTV occurs when a vehicle brakes are serviced and the brake rotor has run out in excess of 0.1mm or 0.004". This run out causes the pads to contact the rotor when the vehicle is being driven "off brake" and after 3-4000 miles, a thin spot develops on the rotor. The rotor run out itself does not actually cause a vibration. It is the effect of the thickness variation of the brake disc or brake rotor under braking that causes pulsation. Even small thickness variations such as 0.01mm will exhibit itself as pulsation. A warped rotor is a very rare occurrence and in 30 years in business, we have seen no genuine cases of warped brake rotors.
The general guideline is that if the vibration happens immediately after install, there is a quite severe run out problem that needs looking into.
Brake discs or rotors should be mounted on flat smooth rust and dirt free hub flanges. Remember that even a small particle of 0.001" under the rotor surface can cause a deviation of 0.005-0.010" at the pad contact point.
If the vibration happens after 3-4000 miles, this is a clear indication that DTV has occurred which is not a warranty condition. The only solution for this is to remove the brake rotor, have it turned by a machine shop, or replace it with a new rotor.
Please understand that the fully automated precision machinery used in manufacturing brake rotors is never likely to produce a distorted rotor. The brake rotor blank is machined with its reference point as the inner mounting face of the rotor as a datum and a "twinning tool" is used to machine both sides of the rotor at the same time. This guarantees zero run out and a perfectly parallel rotor.
If you experience brake rotor vibration, it is first essential to determine if the vibration is coming from the front of the vehicle or the rear. Front brake vibration, or steering wheel vibration, shows itself up as steering wheel flutter. Vibration in steering wheel can lead to serious consequences as the driver may even take the action of releasing his foot from the brake to try and stop the braking vibration.
If the brakes vibration is felt through the brake pedal or the seat/bodywork of the vehicle, it is almost certain that there is a problem with the rear rotors.
National Performance Sales Manager
So, given the many problems seen here with the G6 brake rotors, what say you the group? Is this a case of the vendor blowing smoke to obscure the problem with their product, or could this be legit? I'm still trying to work the warranty issue on the rotors but hope to see replacements soon. PowerStop warranties their brake kits for two years or 24,000 miles as long as they were installed turnkey by a professional shop, not a driveway install (the local Goodyear dealer put the parts on the car). Summit is working with me on obtaining replacements, we're not there yet but it's pretty close.