Hello everyone, im pretty new to this forum.
I just bought my first s2k about a month ago, and i just noticed that the car seems to vibrate at high rpms (above 7)
my brother thinks that it may be an alignment issue. the car is on stock suspension but has 18 inch rims with 245/40/18 tires in the rear, which should be larger than the stock diameter, put on by the previous owner.

what do you guys think

 

RPM has nothing to do with alignment but if you get up to 60-75 MPH and the car shakes then it could be the balance of the tires, and if it cannot drive in a strait line then it is the alignment.

 

I agree that you should check the balance of the tires first. However it very well may be your CV cups are starting to pit. I had vibrations at higher rpms and slowly it crept in towards 5K. Swapped the cups and viola! No more vibration.

 

or your motor mount is lose or broken.

 

More than likely it's the motor mounts. That or wheels not being balanced would be first to check out.