Torsion bar question.

I posted last weekend that my torsion bar measured .855. I have a 66 Dart that had a 273 from the factory. nm9stheham posted a chart in my post that listed the .850 as a 110 lb/in spring rate. It was used in the 6 cy with AC & 318 no AC cars.
http://www.hotrodreference.com/90/mopar-a-body-torsion-bar-size-and-part-number-reference/
That was the first time I saw this size listed anywhere.
As for do they break, When I was younger working for my dad in his garage in the 70's I can remember only ever replacing 3 torsion bars. When they break I remember the bodies hanging all but on the ground. We had to use jacks to get them up on the lift. We worked on many dodge / chryslers as dad spent many years at a dealership but I only remember doing 3 of them.
Rod