Suabru GC Bilstein

I am after some suggestions in regards of springs for a Bilstein PSS9 coilover (old style) on a Subaru GC . The issue atm is the car is on 18" with a set of D2 6pot brakes at the front (soon 2pot rears) . So due to brakes I have to keep the 18" but due to the 18" the coilovers are at full height not allowing the suspension to work properly . I would like to change the springs to longer ones so I can more adjustment and help the struts work as intended . Any recommendations towards length and stiffness?

TIA

I'm rather confused here? Hopefully some of the Subbie folks will add, and correct, where required, but here goes.

The wheel diameter isn't that important, it's the overall tyre diameter, or rather radius, that's the important part. What is your current tyre size, and what's the OEM?

What do you mean by "the coilover's are at full height"? The springs should be compressing at least part way under the vehicle's weight?

The springs should have a code on them, which will give the current rate and, sometimes, the free length - but you can measure that yourself. If you're otherwise happy with the spring rate, you can simply order them in a longer length - with struts 25mm will be around 23-24mm change in ride height - I can't recall the strut angle to be more accurate.

I can't comment on the rate, stiffness, not least because I don't know what the vehicle is going to be used for, nor what the roads are like there.