Perhaps this could be a sticky.

I got off my duff and figured out the various spring rates for aftermarket setups for our car. We're obviously missing the rates for the Eibach Pro Kit, the Tanabe HF, H&R Coilovers, H&R Springs, MazdaSpeed, and JIC, plus whatever else I forgot. Feel free to add if you know them.

TANABE SUSTEC NF210 (Simple spring)
FRONT = 2.9kg/mm -1.4 inches
REAR = 2.0kg/mm -1.2 inches

TEIN FLEX (Ride height adjustable, 16 way damper adjustment)
FRONT = 9 kg/mm = 503 lbs/inch -1.5 inches
REAR = 7 kg/mm = 391 lbs/inch -0.7 inches

TEIN BASIC (Ride height adjustable)
FRONT = 8 kg/mm = 448 lbs/inch -1.6 inches
REAR = 6 kg/mm = 336 lbs/inch -0.8 inches

TEIN S TECH (simple spring)
FRONT - 3.7 kg/mm = 207 lbs/inches -1.4 inches
REAR - 2.6kg/mm = 145 lbs/inch -0.7 inches

 

Here are some more from Alex C.:

https://www.rx8club.com/showthread.p...t=spring+rates

 

Jic coilovers are either 8/5 or 10/7. 10/7 is working great for me!

 

What's the ride like ?

(One of the reason I ditched my 7 was because the 1000 lb springs were killing the ride).