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Message: [QUOTE="James Dean, post: 24457, member: 18501"] When a spring is shortened to have fewer coils it gets stiffer. 1/2 as many coils is twice as stiff. 1/3 as many coils is 3 times as stiff. 2/3 as many coils is 1.5 times as stiff. ----------- Using springs in PARALLEL like your forks allow you to just add the 2 stiffnesses for twice the stiffness. K = k1 + k2 So you can get a rate half way between by using different spring rates in your fork. ------ Using different rate springs in SERIES like a PDS spring, follows a much different equation. K = (k1 + k2)/(k1 x k2) The resulting spring is softer putting them end to end. The progressive wound coils in the PDS and other dual rate springs need to bottom against each other to get to the higher second spring rate. (K = k2) This is why the coils are close together at one end. [/QUOTE]