Spring lenght selection

[marcg]

I have tried to figure out what lenght of spring I should use for my coil over conversion. On my last 240Z project I used the long (12") AFCO springs vs the 10". Now I find myself with much shorter set of springs (6") with the correct rate and cannot see a problem with using them (as long as they do not coil bind at full bump). Packaging wise the 6" spring would work very well. I have looked through several suspension books and websites but there does not seem to be a rule of thumb when selecting spring lengths. What would be a good guide? Any sites that would enlighten me?

Thanks.

[johnc]

Based on your spring rate you heed to determine how much compression travel is left in the spring with the vehicle sitting on it. For a strut suspension on a car driven on the street you'll need about 3" of travel before coil bind. That means, at static ride height with two people in the car, full fuel, etc. a 6" spring shouldn't compress more then 1 to 1.5".

 

For a typical street 240Z you have about 650 lbs on each corner with two people in the car, full fuel, etc. That means a 6" spring would need a rate of about 600 lb. in. to safely keep from coil binding. That's stiffer then any spring run on a racing 240Z.