Been looking at lowering spring for CT9A
Most of them is progressive rate

Linear or non linear rate as follow:

Gtworx/RCE spring(Front is linear, rear is progressive)
Rigid Japan(Made to order, super expensive, front/rear is linear)

Is there any other option I miss out?

 

Cant go wrong w/the GTWorx / Swift or even the Eibach. I ran the Eibach as my first EvO lowering spring (They work great & have a nice firm ride)

 

I ran the GTWorx / Bilstein set-up for a few years with Tein camber plates. Really well rounded set-up. I highly recommend it.

 

GTworx spring is no longer available new
That's the closest thing to a linear rate spring, with front being linear and rear being progressive rate
Seems like there are no real alternative

 

www.sparktec.motorsports.com

They have a link on there for buying them. Maybe they have new old stock?

 

They might have old stock, or will tell you when ordering they arent available. I asked GTworx directly and they said no dice.

 

Oh dang, sounds like GTWorx just didnt sell them fast enough to buy another batch. To bad too, those really were the best springs for an Evo. Good rate, not over-lowered, linear. I still have mine on the shelf incase I ever turn the Evo back to a street car.