Good info but there is a"Swift Spring" upgrade. This option runs approx $350 more.
I do believe you are going from a Progressive rate spring to a Linear spring.
http://blog.modbargains.com/linear-r...best-4-street/
NOW OFFERING SWIFT SPRING UPGRADE OPTION
SWIFT Bronze Metric Coilover Springs are highly linear, fewer winding springs that reduce unsprung weight and increase performance. Swift springs are special order and assembled onto your shocks with proper preload. Please allow 3 weeks.
for more information look here. This details the H5S.TW material that sets Swift apart from the competition. We suggest Swift springs on any vehicle that will see the track due to the unsprung weight and predictability. The dailiy driven street cars these springs are probably overkill.
BC Coilovers are now available with SWIFT springs as additional option for your BCs. For those of you who demand a higher quality spring for street and track.
These are the flagship product that made Swift a regular name in some of the most prestigious race series around the world. From Formula Nippon to Le Mans, these innovative products continue to make Swift a staple in the racing industry.
Through the input of numerous race teams from across the globe, it was apparent that there was still room to improve upon the conventional racing spring. Swift engineers spent countless hours conducting research, developing and testing the springs in order to create the perfect racing spring.
The Swift engineers and in-house metallurgists were able to formulate a unique blend of metals they have named H5S.TW, this unique alloy hosts a wide range of benefits and virtually zero drawbacks. The end result was the creation of the Swift Metric Coilover springs.
The Swift Spring upgrade at the time of purchase with the initial set of BC Racing Coilovers is $260.00 on top of standard coilovers.
Swift Spring Technical Advantages
Swift proprietary material along with advanced cold winding process allows Swift springs to be manufactured using a thinner wire diameter with fewer coils making the springs the lightest magnetic metal springs available on the market.
Swift Accuracy
Swift Metric Coilover springs feature the highest linearity of any spring out there. Along with the widest stroke range possible, the springs stay linear throughout MORE of the usable stroke range compared to anything else out there. Swift guarantees the spring rate accuracy to be +/- 2% within the advertised spring rate!
Industry leading spring response
Swifts superior spring compression speed responds much quicker over undulating road surfaces so the tires have a lesser tendency to skip. This enables the tire to stay in contact with the road, improving traction and helps keep tire temperatures down.