2003 350Z winter tires

First of all welcome,
I am not trying to trash on you but you need to do some research before making any and all purchases.
www.my350z.com is a good place to start, and I highly recommend you start doing some research before making any further purchases.

As for your tire selection, you exceeded the maximum 3% increase
http://www.1010tires.com/TireSizeCalculator.asp?action=submit

A few things you might want to look out for…
Have you seen your SLIP light come on?
This could cause problems with your VDC as well.
Also the 3% increase over OEM, can potentially cause brake problems.

Best of luck