Dylanamus

1990 CR-X SiR (JDM EF8 with B16a) 960kg.
Currently: new ITR Koni Sport shocks all round with GC coilover sleeves and GC top hats.
Front: 8.1kg/mm (450lb/inch) Rear: 6kg/mm (350lb/inch)
All front bushes are polyurethane except the fork eyelets and are in good condition. The rear has new OEM trailing arm bushes, new OEM LCA bushes and the rest polyurethane all in good condition.

Stock front swaybar. Solid whiteline rear swaybar for ED CRX.

Camber is at -2 degrees on all four wheels, but I can't adjust it except by altering ride height.

Toe is set at 0 degrees front and rear. Castor is within acceptable OEM standards.

The car handles great on smoother surfaces, but as soon as it hits a sharp or deep bump the steering yanks hard and there is either bump steer or wheel skipping. Heavy braking is squirmy over all but the smoothest of surfaces.

The roads I mostly drive on are all tarmac, but poorly maintained. My previous setup had 12kg/8kg springs so I thought 8/6 (linear) would be soft enough for these roads. Symptoms suggest I was wrong.

The kind of driving I do is a combination of daily driving and public road hill climbs, where the surfaces are tarmac but scattered with imperfections, some quite harsh. I never drive offroad.

Keeping in mind the CR-X, even only half lowered, has very short suspension travel compared to most other cars and that I do have some urethane bushes...

...What spring rates, whether linear or progressive would be more suitable for my application in your opinions?

I look forward to your feedback!

PIC Performance

What is leading you to suspect your spring rates? In what sort of condition are your front upper and lower balljoints, and the tie rod ends?

Dylanamus

From the inspections of two mechanics and myself, we cannot fault the balljoints and the tie rods are brand new.

I should clarify the "bump steer" is probably technically not the correct terminology as the steering wheel does pull with the movement of the car.

What mostly leads me to believe it is the spring stiffness is the harshness when hitting rough surfaces compared to both OEM springs and Tein SS coilovers. However a year or more has passed since I last had the Teins on, so I'm open to any suggestion blaming other components.

uniseriate

Different car, but the Silvia crew suggest lower spring rates than what you have for hill climbs in this thread.

I would stick with linear springs. Most "progressive" springs do not change their rates evenly when under deflection. The abrupt change from a low to high rate makes for some interesting handling issues.