Hey guys, i installed those tires(225-50-18) last Friday. Here is some of my initial impressions:

-Much much quieter than the stock dunlops
-Ride comfort is much improved (stock dunlops were harsh)
- Steering responds is much improved (steering afford is noticeable lighter at parking lot speed and the respond is more precise at higher speed)
-dry traction has a marginal improvement (My driving style is some what aggressive)

I'll find out snow and wet traction later on this year (montreal is famous for its snow/rain mix). Those tires are definitely one of the better alternative available for g35 XS.

 

thanks im in the market for some tires and these were one of my options

 

No problem, they're very good tires. I found that there isn't a lot of tire options available for xs' wheels. However, you could always size up to 235-50-18 to get more choices.