Whats the widdest tires i can put on my z with stock rims, i have the 17s. Thanks.

 

I have Bidgestone 275/40/17 on my Z. Traction is increase dramatically. It changes the driving (cornering) a little bit, so watch out until you get used to them. In addition, I put the 235s from the rear on the front to help with steer.. ummm can we say fun..

 

I have Nitto NT-555 245/45-17 in the fronts and 255/45-17 in the back.

I have pictures of them on my car at this thread:
https://my350z.com/forum/wheels-and-tires/124446-wider-tires.html

 

Here's Yokohama's fitment chart...
http://www.yokohamatire.com/utrimwidth.asp