The 1.24 TBs are rated at 425 lbs/inch, but when compared to coil spring I know the stiffness rate is a little higher... maybe ~550?

Mopar Mitch "Road racers and autocrossers go in deeper and come out harder!"... and rain never stops us from having fun with our cars... in fact, it makes us better drivers! Check out MOPAR ACTION MAGAZINE, August 2006 issue for feature article and specs on my autocross T/A!