the ride on the 18's is great. the road feel is so much better than the 16's. as far as stiffness goes i think that it is very plush. i just got back from a roadtip to millwaukee and it was not harsh at all. i still want to change the suspension to make it stiffer. THIS IS THE WAY THE CAR SHOULD HAVE CAME. these 18 inch wheels are lighter better looking and handel much better.