trying to diagnose a horrible jutter at 70+ mph. i've gotten mine balanced twice but it seems to get worse each time.

 

Have you tried a different shop? Either they don't know what they are doing or there is a bigger problem. Could be a slightly bent wheel, I have heard warped rotors can offer a similar effect, un-evenly worn tires as well. Can you see signs of weird wear anywhere on the tires?

 

well, the tires don't look really bad or anything and my alignment was pretty spot on before they adjusted it, only tiny adjustments here and there...

wheels are definitely not bent, i checked that

rotors are brand new DBA (2 months old)

i'm debating on just going to america's tire for the balance

 

Does your wife or anybody else drive your car? Have you checked the camber arms? My G35 had a bad wobble at or near 70mph and it ended up being a slightly bent camber arm. Prolly not your issue but something worth looking at.

 

If I had stock wheels, I wouldnt mind--however, I left them at a "friends" house, and they disappeared.

This might seem stupid, but are they torquing your wheels to 80-85 ft-lbs? You might try using a breaker bar, loosening the nuts, and then re-torquing to 80 ftlbs as per G spec, using a proper "star" configuration tightening protocol.

 

yup, definitely torque'd properly...i have taken the wheels off myself on a few occasions to see if i can find any bad bushings or anything. but at 46k miles, i'm doubting its a bushing.

i regularly work and build cars so i'm not new to doing things.

 

no hub centric kit? Occasionally wheel weights fall off as well or balance comes off. Sometimes there balancing it wrong or a simple dismount and remount spin it 180 on the rim helps as well.

What type of tires do you have on there?
Does it stop shaking after a certain speed?

 

its oem coupe 19's on my sedan, hankook v12s which seem to be more prone to cupping.

dealership just rebalanced them again and they are the same.

 

have they checked your axles? It definitley has an issue if its still shaking and the tires are balanced

 

checked the axles for play? rwd doesn't have axles in the front and i don't think the rear axle could make the vibration feel more like the front & steering wheel

 

That problem sounds weird as fk. I read that you have new DBA rotors. I did read something a while back about someone getting new rotors and complaining that there was wobble. Perhaps they were installed incorrectly? At any rate, good luck with that. Have you tried posting on the main board as well?