When does your rear suspension reach full droop. I would think when you jack up the rear of your car? Any other time?
What length and spring rate are you using?
I used 10 inch springs with rates from 225-300 lbs.
IT does depend on what your car weights and what mods you have done to the suspension. A torque arm rear will need higher rates then what I used.
"Drag racing is for those people who don't know how to down shift and brake at the same time. "
DD '12 VW Jetta TDI, Race car '87 ITA 16V Scriocco
Cars owned: '86 Mustang GT, '92 Mustang LX, '93 Mustang Cobra "R" #58