I've seen the formula for calculating effetive spring rate of a torsion bar, but honestly i don't know the inputs for 2 (arm length & effective bar length) of the 3 variables.
http://www.proshocks.com/calcs/torsionrate.htm


Anyone already done this?
Looking to know effective spring rate of 18-23mm solid & 21-23 hollow.

search. its been posted here 2 or 3 times.

maybe we can add it to the tech info part of the site.

SEARCH is upper right of page in gray shaded box

here is one thread with conflictng asnwers..
Search result #1

Use these dimension on your Calc Pgae.

Bar Length = 21"
Lever Arm = 14.25"
Bar Dim. = your selection

Ken

just use this table...
http://instant-g.com/Data/911CoilConv.html