Not being combative. I'm an engineer and I was looking for a response like you gave the second time around. Thank you.
And yes, this is sledpulling, we do run a shit ton of weight up front. And the valving interests me quite a bit. Hardly anyone is doing it AFAIK, aside from the Super Stock guys.
If I read you correctly, it would seem that the torsion bar spring rate is low compared to the coilover example (at roughly stock ride height, not peak) Correct? Because the front is so damn limp as soon as we let off the throttle. I believe this is great for keeping hop out of the truck, but maybe it's too much of a good thing.
For reference, trucks with stiff leafs in the front (Fords) are just horrible pullers and hop like a nightmare. I have slo-mo video of one where hop in the rear reflects into the front and the whole thing goes into oscillation quickly.
The coil over Dodges have few issues.
Got ya, I may have "read into" your post then, hence the assumption.
I need to break your comment down further to explain this better.
As for the amount of lbs it takes to hold the truck at stock ride height, there are a few issues for comparison (I'm only talking the amount of lbs/inch to achieve ride height). If mounting points were the same for both springs and say the torsion bar is 1000lbs/inch verses a coil spring with 800lbs/inch, either spring will still take the same amount of lbs to hold it up but the coil spring will compress more to achieve it. So to make the coil spring match the torsion bars ride height, the coil spring will need more preload. in the end, if it takes 3" from the torsion bar to achieve ride height (3000lbs on the torsion bar from vehicle weight), the coil will need a total of 3.75" of preload to reach it.
Now the factory mounting point of the torsion bar has a 4:1 ratio on the control arm. This means you have a hell of a spring rate in the torsion bar to achieve desired ride height due to leverage. So the spring rate is ridiculously high to compensate for that leverage but like you pointed out, in the small amount of stock wheel travel, you can easily unload those bars to a very light amount of spring load when your pulling and as you hit bumper or get a hop, you get drastic changes in spring load.
With a coil over, your leverage with the LCA changes to a ratio much closer to 2:1. This allows a lighter spring rate to be used to achieve ride height over the torsion bar and a much better progression of spring load as it is loaded and unloaded (you won't go from a 10k load to 1k load in 6" of wheel travel like a torsion bar). That allows shock valving to be much more effective and easier to tune in. In my world, you only want a spring to hold the truck up by a certain amount of preload, the rest of the control is done with valving on a single spring rate shock setup, beyond that you create a rough ride or weird valving characteristics that won't work well. Too low and you can run into coil bind issues to just get ride height and heavy valving that will heat up a shock quickly. You can achieve more spring load onto the LCA due to preload into the spring but when the front end rises, it still took x amount of spring load, weight transfer, and leverage on the ass end to make is rise to that height. Adding more preload might work to a point, then it will just cause the front end to rise more when you take off. You will have a wider range to adjust though on a coil over than compared to a torsion bar. It's a combo of things helping, the better spring position with leverage, better spring rate, and better valving to match. I wouldn't get hooked on the fact the spring puts more load on the LCA as much as the valving and better spring rate help control that front tire much better.
My terminology may not be spot on so just ask if unclear. Sometimes I have a hard time describing what I want to say in text lol.
