I just bought a set of stock 18" wheels from an '07 g35. They currently have 2) 225/50/18 & 2)245/45/18 tires on them. I need new tires. What is the widest tires I can run? Or, should I stay with what is on them? I also, have to get lug nuts. Any ideas on a good place for those?

 

I assume you have a 03-06 sedan. If so, 225/50/18 is .55 inch larger diameter than stock 215/55/17. 245/45/18 is .37 inch larger than stock.

235/45/18 is the same as stock, but not a common tire size.

The tire calculator on discounttire.com is good for figuring out the affect different tire sizes have.

I have 225/50/18 on all four wheels.

 

i'd do 245/40 up front and 255/40 in the rear.-
-GP-

 

In regards to lug nuts, I went to various auto parts stores. They all told me I needed the OEM lug nuts. After a while I broke down and bought from the dealer. Not cheap, but they are correct. I checked with Nissan and Infiniti dealer. Infiniti was cheaper.

 

Yes, I do have a 2004 Sedan. I am wanting to go as wide as I can. I believe the guy told me the front wheels are 7.5 & the rear wheels are 8.5, does that sound correct?

 

I would go 235 and 255.

 

....& stick with the 50's & the 45's series?

 

no, the 2nd gens run a taller oem tire. If you went with 235/255, you'd want 235/45F 255/40R.
-GP-