How can your wheel gap be smaller from adding new wheels? Did you not maintain the original overall tire/wheel height? If you changed the overall tire/wheel height and didn't lower the car, how much did your ground clearance increase? How much of a speedo error did you introduce?

No offense, but after looking at your photos the wheel gap looks about the same to me. Not the best photo, but compare here:

 

I went with 18x8.5 wheels with a 45mm offset. This moved the tires and wheels much closer to the fenders than the stock 17" wheels, which are way too narrow and far set into the wheel wells. This alone dramatically changed the look and stance of the car.

I also went with 245/45/18 tires, these tires are slightly taller (only .03" taller)than the stock G35 Sedan tires (which look lost in in the wheel wells) this helped fill the wheel well much better and in no way took on a "4x4 look". The 45 series tires do not effect the ABS, Computer, or VDC system.

Sorry about the bad picture, the difference in look is huge. The cars stance is much improved, the 18" wheels with a little a taller tire get rid of the "skateboard" look of the stock 05 Sedans. This last weekend I had to drop by the dealer to pick up some stuff for our Coupe, and two salesmen and three customers all commented that Infiniti should have outfitted the Sedans with a wheel and tire package like mine.

 

I was looking in a Consumer Guide book and here are the ratings for ride quality:

Sedan, auto: 7
Sedan, AWD w/Prem. Pkg,.: 7
Sedan w/Sport tuned susp. pkg., auto: 5
Coupe w/Sport tuned susp. pkg., manual: 3
Coupe w/performance tire pkg., auto: ?
Coupe, auto: ?

Does anyone have an idea of where the ride quality stands for the Coupe automatic without the susp. pkg?

 

If you look at the ratings for Michelin Pilots in CR, they are ranked fairly high, but not recommended. They did not score well in road noise and such. That might explain the ratings.

The stock setup is with perf. tires. The bigger you go the rougher the ride is going to be with a low profile tire.

 

Also remember, that with low profile tires there is less sidewall. The sidewall is also stiffer and therefore the tire will ride harder. I don't mind the stiffer ride because of the advantages the lower profile tires make in the handling department.