I've got the stock touring 18" rims... wondering what I should expect by switching to lightweight 18" rims ie lmgt4 or volk te37... thanks!

 

I recently changed my stock G35 18"s to Track Rays. The different is there. It is noticeable. I think it's worthwhile if you can get a good price on the lightweight rims. On the bathroom scale the stock rims/Pilot sports were 50 lbs, the track rays/potenzas were 46 lbs. And the Re040s tend to be heavier than the pilot sports.

 

I have 18" rgr with fat tires... I weighted them last year against the stock 18"

If I recall, it was something like... (more or less)

bbs 18x9.5 + tires 265/40-18 = 45lbs
stock 18x8 + tires 245/45-18 = 53 lbs

that makes 7-8 unsprung lbs per wheel difference.

car does feel a little "sharper" in handling and braking. Acceleration feels the same