14-Up RAM 2500 2 Inch Rear Performance Spring Kit ICON Vehicle DynamicsICON engineers have also developed optional Performance Systems that include multi rate rear coil springs in place of the rear spacer. The lighter initial rate of these performance rear coil springs helps the truck feel smoother and more controlled over washboard roads, small whoops, or similar terrain. The secondary rate allows the truck to maintain exceptional ride quality over larger obstacles, while at the same time retaining factory payload