This is false. The spring rate does not change significantly. That's why you can have leaf springs re-arched. You can even have torsion bars reconditioned by Firm Feel. That would not be possible if the springs lost rate. The spring constant of the metal is not based on its age or use, it is determined by its metallurgic composition.
Exactly. I would say no smaller than 1" torsion bars though. 1" bars are still pretty compliant, and give a good ride quality with quality shocks. I had 1" bars on my Duster for awhile, upgraded them to 1.12" bars to get the performance I wanted.
