Originally Posted by triniemi
I measured the current springs (at our gym
). The spring took 400lbs to compress it one inch. Way too tight? Free lenght is 7" and they were installed at 6". I'm considering to order the 7" free lenght 300lbs springs. Can I now calculate how much I should preload the 300lbs springs to achive the same ride heigh?
each spring needs to hold up about 658# per side according to your scale report. So if your car was at the correct ride height meaning 3/4 +- shock ram showing above the bumper with the dimensions you just gave, then the new springs will require a higher setting to maintain the ride height. Go 658 divided by 300 = preload in inches to hold 658# that is 2.19 at ride height not what the platform needs to be. You have left out the spring ride height or strut travel dimension for the calculation. If you want to guess, the platform may need to be 3/4" higher than it was. Remember that you can easily change the spring platform when you lift the car back off it's feet. I would recommend that you try the 3/4" higher or 5.25" at ride height and take a look at where you ended up on your ride height. Unless you are installing this strut on the moon where you don't have an oppertunity to adjust it, you might just need to make one final adjustment to get it perfect and I feel that the work is worth the time.
Sorry I can not give a more pointed answer with the info available, but you should be in good shape from here wont you?
Good luck in 09