It's a 2008 G37S manual.

The symptom is a high frequency vibration that is felt through the stick shift, and the steering wheel. It is not at all like the vibration felt from a warped rotor or a unbalanced wheel. The vibration is a lot like that of one of those massage machines. It only occurs at higher freeway speeds like 70+.

The issue only started to present itself after the tires were changed. The vehicle still uses OEM 19" wheels. Tires were changed from stock to Yokohama S Drive tires. Fronts were increased to 245/40, and rears were increased to 255/40.

I can't figure out the cause for the life of me. Everyone I've talked to about the issue is stumped as well.

Any thoughts on what might be the cause?

or even what I can do to help determine the cause.

Thanks for the help!!

 

is all 4 tires mounted in the same direction? check that!
did they balance the wheel correctly?
have you ever ran into a curb?
you should've went 275-35 in the rear

 

Best advice I have, is to try a road-force balance on all 4 wheels

 

Thanks for the tips, but it really doesn't feel like a unbalanced wheel type of vibration.

 

Its possible that you could have gotten a bad tire with a shifted belt or something internal.

 

Alignment need a touch up maybe?

 

In years past, when I first got my z28 (4th gen) at speeds above say 50/60 mph, the car would hum. It wasn't a continuous hum, but cyclic. It was felt all throughout the car, seat, pedals, shifter, etc.. Replacing tires didn't help matters. After some research, it turned out the GM used steel drive shafts on these car (propeller shaft as referred to in the FSM). The problem was, they were not properly balanced. The solution was to either rebalance, or use an aluminum one. I chose the latter solution. The car still had the issue, but the humming was now at 80-90 mph. This wasn't a perfect solution but was acceptable given I don't normally drive at those speeds.

As for the G, if the only change has been tires, then I'd definitely look into that as being the cause. Although I doubt a roadforce balance will fix your problem, it's worth a try. I would think that if you had greatly differing lateral forces at play, the car would pull one way or another rather feel like a high frequency vibration. I would also assume who ever is balancing your wheels is doing a dynamic balance instead of a static.

 

What Weiboy said... And

Are you still using the OEM lug nuts or have they changed??? It is important that you use the OEM washer type lug nuts with the OEM stock wheels.