I have a 07 G35S with 4WAS, and I was wondering if first I can change my springs if I have that, plus if the H&R springs are any stiffer than my springs since I heard G's with 4WAS have stiffer springs than regular sport models.

 

Can't speak for your specific model but I found that the H&R's were actually SOFTER than the OEM Sport springs. The rides a lot more compliant now as well.

 

Overall your ride is softer even with 20" wheels?

 

There is a lowered G35x in the stickys.

 

Yes. But then again, several psi lower in the tires with stock suspension may have changed that impression. I never got around to checking my stock wheels to see if there were over inflated like many other members' had found theirs to be before I swapped out for the 20's.

 

My father put H&R Springs on his 03 coupe. They lowered the car about 1 1/8 an inch. The ride was as smooth as OEM during normal driving conditions. In cornering you can def. tell the diff in the handling. The car stuck to the road very nicely, and handled better than stock. But during rougher driving conditions, the springs still had a little more bounce vs. OEM. I know theres a diff in the coupe and X, but maybe will help you out :-)