From
Forged Performance: JRZ RS1 Coilovers **Review** and Press Release :
"Linear Rate main and helper springs: 6 X 2.25 650lb Front 8 X 2.25 500lb"
I imagine that's what's written on the spring boxes if I go dig for them in the garage (650 and 500), but I'm eating pizza right now :P Unless they changed something with this setup since then.