Brake Vibration - Need diagnosis tips

Brake vibration in my '97 GTP is driving me nuts. I know Pontiac undersized the brakes in these cars but I went the first 85 kmi with vibration free brakes and want to get that condition back.
I've replaced front pads and rotors and even had brand new rotors trued by a machine shop and the vibration continues. There's no vibration at low pedal pressure or hard pedal pressure, but at medium pressure that's where the problem is.
The latest rotors are Raybestos PG Plus and the pads are PF carbon metallics.
1. The caliper pistons seem to slide smoothly and the pins are lubricated. Is there any way to diagnose sticking caliper pistons??
2. I'm 95% sure my problems comes from the front end but how can I eliminate the rear brakes as the culprit for the vibration.
3. I plan to check for bad hubs/tie rod ends using the shake the wheel method at the 12 and 6 o'clock then 3 and 9 o'clock positions. Is there a better diagnosis method?
4. It seems like vibration started when I switched from OEM to Ceramic and then Carbon Metallic pads. I'm wondering if there's just an inherent vibration that comes about by using pads that are adherent vs. abrasive pad design.
5. I plan to make another attempt at bedding in the pads. I'm not sure I ever got them hot enough for the proper bedding in/material transfer as suggested here.
http://www.stoptech.com/whitepapers/warped_rotors_myth.htm
6. I also plan to check runout and will try and index the rotors in hopes that might help.
Any other suggestions??? I don't want to indescriminantly replace parts in the hope of it solving the root problem.?
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Do you possibly over-torque your lug-nuts?
This will temporarily (some times) warp the rotors.
I'm trying to figure out what a GTP is.
In any case, newer cars come with cheap, thin rotors. Easy to warp with overtorqued lugs. Perhaps the rotor is fine when slow because it doesn't get as hot. As it gets hoter, the lugs might find it easier to bend the rotor some...
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check the wheel bearings
davefr wrote:

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How??
wrote:

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Don't forget about the strut bearing(s). My Grand Prix had problems with seized / worn strut bearings at 70k miles.
It caused memory steer, where the vehicle would pull to the right after making a right turn, and would pull to the left after making a left turn. It wasn't a bad pull, but if you let go of the wheel, it'd drift.

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snipped-for-privacy@hotmail.com (davefr) wrote in

Just for sh*ts'n'giggles, get you a set of Raybestos PG Plus pads (mid grade) and see if that eliminates the problem. The $17 for the extra pads is worth it if it saves you from spending a ton more money on things you don't need.
--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
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Are you sure it is not the rear rotors or brakes? I assume the the rear parking brake is a internal type in the rotor, if so then it is harder to isolate the rear, why don't you indicate the rear rotors for runout.

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General motors designed some of the crappiest brakes for the Grand AM and Grand Prix models. This has become such an issues with GM, that dealerships are being supplied with special correction plates/shims to compensate for lateral runout. I'd bring it to the dealership...
The unitized wheel-bearings used in GM vehicles are also notorious for failure. However, they will usually make a loud humming noise when they go bad, and generally can't be felt through the brake pedal.
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