I concur with DTMenace above. You probably won't get much sympathy from anyone on trying to make the ride in the Crossfire softer. But you're not alone in saying the Crossfire ride is somewhat harsher than you expected. But I think I remember someone verifying that the maximum tire/wheel diameter the Crossfire could take was 27 inches (685 mm). The tires you're suggesting exceed that figure if you are going to use the OEM wheels. You will probably have to go narrower with the tread width to find something that works. (Note: A 235/40x19 should work, but I'm not a fan of going narrower on the tire. You will need to verify that the narrower tire will work on a 9" wide rim like the Crossfire has in the rear.) But if you use that 685 mm figure, you could shop around to look for a combo that would address your desire. But I don't think you will have many options. Others may chime in on this. Your options are better if you want to include smaller aftermarket wheels or find another pair of Chrysler 18" wheels for the rear - some owners have done this for a variety of reasons (e.g., tire rotation, etc.)..

You can use this link to compare OEM to aftermarket wheel/tire combinations. CLICK