Originally Posted By cataclysm80

I notice that these rates don't quite match the Firm Feel advertised rates.
http://www.firmfeel.com/b_body_mopar_torsion_bars.html

My guess is that Firm Feels lower control arm measurement is about half an inch longer. Perhaps they measured all the way to the end of the lower control arm, instead of stopping in the middle of the ball joint mounting hole?
This illustrates why it would be a good idea to calculate the rates if you're comparing torsion bars from different vendors. How they measure things can affect their advertised wheel rate.


FOR THOSE OF YOU WHO ARE MORE EXPERIENCED, IS MEASURING TO THE END OF LOWER CONTROL ARM, INSTEAD OF TO THE CENTER OF THE BALL JOINT MOUNTING HOLE A BETTER METHOD?


The Sway Away calculator shows that for their applications, which is a kind of neat, but still not exact since they are factoring that for their sprint car applications. So there could be some slight variations to raw geometric calculations. However, what could be the impact on their t-bar rate calcs is whether you use the entire torsion bar length from end to end vs using only the active portion between hex ends up the radius. Since they point that out on their active length number, I'd imagine the Mopar version differs slightly from their sprint car version. What we don't know is the spline size they are using to determine their active length and how that translates to to the Mopar hex ends to active length relationship.

IMO, differences under 10# aren't easily seen on a stop watch, never mind the butt dyno.