I'm thinking about changing my wheels on my S430 from stock 17" Star wheels to 18" AMG wheels.
I have done this before with mixed results:
I went from 16" to 18" on my 1999 S class and altough it looked great with the AMG wheels, the ride definatley suffered.
I changed out my 15" stock wheels to 17" AMG wheels on my 1995 E class and the ride was actually better.
My 2001 S430 currently has the stock star wheels with 225/55/17 Michelin Energy Plus, which rides very smooth.
What do you think will be the difference, if any if I upgrade to 18" AMG wheels and 245/45/18 tires? anyone else done this?? I prefer a luxury ride to a sporty ride. Thanks for your input.

 

I think your answer will totally depend on the tire you use. With a good tire IMO You shouldn't notice much of a difference.

 

I have an '03 S430 with the AMG Sport Package with 18" rims, 245/45 fronts and 265/40 rears. It's rides very nice. In fact, I just went to 20" and the ride is still nice, although you can feel pavement irregularities a little more.
I'm in CA and have the 18" AMG's for sale. They are equipped with Michelin Pilots. See my classified if interested.

 

I agree...tire and tire pressure dependent.