Here's the spring rate difference from an article about the Crossfire............Both the Chrysler Crossfire SRT6 Coupe and Roadster models benefit from stiffer spring rates which are tuned differently to optimize their own handling characteristics compared to the original Chrysler Crossfire. The Crossfire SRT6 Coupe’s spring rates are 451 lb.-in. in the front and 480 lb.-in. in the rear, while the Crossfire SRT6 Roadster’s are 434 lb.-in. in the front and 491 lb.-in. in the rear, compared to 303 lb.-in. front and 337 lb.-in. rear on the original Crossfire Coupe and Roadster models.