Lower Spring Rate Torsion Bar options - LML

[TowU4Free]

As the title states I am rolling around the idea of a lower spring rate in my truck. The BDS Coilover kit is what got me started down this rabbit hole and it appears 2011-2014 trucks came with 5 different options (See attached photo).

My CCSB 4x4 has the 5200lb gross weight AAF & AAG springs


My truck currently has factory suspension and keys with the keys turned up (driver side is maxed). Truck currently sits exactly 1in lower in the front and truth be told it drives very smooth. My CV angles etc. are not way out of proportion and the bump stops have plenty of room for movement.

The reason i bring this idea up is i am thinking maybe 1/4 to 1/2 higher in the front would be optimal aesthetically and it would seem that i can step down to the next lower bars down by #400 and achieve either the same ride quality i have now, or better utilizing an aftermarket key and going up only a hair.

This should be possible since when the bars are "torqued/turned up yada yada" they're not "tightened" and the spring rate isn't technically changing. The only thing changing is the angle at which the lower control arm is at or in other words, the leverage the control arm has on the torsion bar itself which is what makes the suspension stiffer since the leverage angle is different. I'm no pro in geometry or suspension by any means, but based on my research and experience over the years with a few trucks this looks to be the logical reasoning.

So on to the question-----Has anyone done this before? If not, Still would be curious what everyone's torsion bar codes are (sticker on the bar itself with a part number and 3 digit code). I'm guessing the gassers had the lower spring rate- still trying to determine that.

Any thoughts are welcomed as are opinions.. Lets keep the opinions educated please. Hopefully this can be informative for others at minimum.

For reference:
2015 LML
326/60/20 Toyo AT3's on stock wheels
Stock suspension
Billsteins on order

 

[Bdsankey]

You'd want to step up in weight if your goal was to lift the truck.


As for if it's a good idea or not, I would personally recommend you get a 3-5" lift and turn it all the way down until you're happy with it. The front end geometry will thank you greatly.

 

[TowU4Free]

Thanks Bdsankey, My goal would be to use aftermarket keys to go up but a lower spring rate essentially canceling out the change in geometry.

My previous truck had a Cognito 4in kit on it turned down with no blocks in the rear for race purposes.. It did not ride well after all said and done because the front end was so soft and the rear was stiff due to no modifications to the leafsprings and the front bars being too low to provide enough spring rate. Perhaps i could get away with it on this truck with a 1in rear block depending on lift kit. That's something i have rolled around the idea of.

 

[Bdsankey]

So here’s the issue, you want more lift and you’re already maxed out with aftermarket keys on those codes springs.

You need more spring rate not less to get lift without doing it properly. If you lessen the spring rate you get less force applied to the control arms per degree of rotation of the keys

 

[TowU4Free]

Correct, however I am running stock keys currently. By taking an aftermarket key which is indexed differently and using a lower spring rate torsion bar it would appear to me you can get some lift by using the aftermarket key and the spring rate will still be a tad less than what it was prior since i'm not talking "cranking down" on the aftermarket keys. Aftermarket keys will allow slightly more degree of rotation on the bar, in this case the lower spring rate bar.

 

[Bdsankey]

I was under the impression you were running aftermarket keys.

I still think changing the springs is not the best way as you’re going to still be using them for 100% of your lift. For the money you will have intorsion bars you could likely piece together a decent lift. It could work but if it doesn’t you’re out 100% of the cash for those torsions.

A customer just brought us his 14 that he installed keys on and cranked them to the max (sure, slightly different scenario) but he didn’t realize to check droop clearance and the upper arm was already in contact with the stop. You have clearance now, how much will you have with another half inch to an inch of lift? Will you have enough for proper suspension articulation?

 

[Chevy1925]

What you are after will effectively work. You don’t need more spring rate for more lift, only if you plan to keep the keys in the same exact position. Since you plan to change that as well, you can get more lift with a lower linear rate spring (spring rate). Problem is, we don’t know what the max twist is allowed in the torsion before permanent deformation happens to the bar nor do we know how much cycling the bars can handle before sag occurs. I would bet that there are guys out there on the bars you plan to run, running cranked without issue though.

Question is, will you notice the difference? Personally, I’d crank what you have now with aftermarket keys and see how it rides. Go over a “control area” were there is rough spots, small bumps, sped bumps and so on, then change the bars and crank to the same height again. Run the road and be honest with yourself. Don’t let the placebo affect take hold. You will be splitting hairs here so don’t expect a massive difference. Where you will notice the difference the most is in larger hits like coming off curbs, speed bumps, pot holes and so on.

I would run the lowest spring rate I could to run the desired ride height and then custom valve shocks to it. The shock valving will give a huge difference.



The hard part with torsions is you can’t add height to the truck without increasing spring preload. On a coilover truck, you can engineer ways to add height and not affect spring preload.

 

[TowU4Free]

Hey Chevy1925, I agree and I am terrible at splitting hairs. I will obsess over an exhaust tip angle for days until its "just right". I'm willing to give it a try if I can find some bars used out of a part-out truck. If anything, for others down the line thinking of an alternative. It may take me some time to find some but I will update when I do.

 

[Chevy1925]

the lower the miles, the better. springs wear out just like everything else. something with 200-300k will give a different ride characteristic than ones close to new

 

[TowU4Free]

I just found some off a 16 High country ccsb Gasser (4800lbs) truck still has window sticker so i think it may have fallen off the transport truck (0 miles) and they also have an ecsb that looks very clean with the 4400lb springs. I have inquired about all 4 for a deal. We shall see.

 

[TowU4Free]

Just secured a set of 4800 and 4400lb bars off 0 mile trucks. It may take me a few weeks but I will update once I try them all out.

 

[Chevy1925]

awesome!

 

[TowU4Free]

Want to give you all an update who may be waiting to hear. I received both sets of T-Bars pretty quickly, I did the ReadyLift control arm install myself and marked the cam bolts before removal. After I got those on and new keys i've got it just shy of level.

Here's the kicker... I decided to try it with the stock bars first and would you know it drives just fine.. Smooth enough to where when i hit a bridge at the bottom of a hill you can still feel plenty of up/down soft movement in the front suspension (think 1980's Cadillac) and bumps etc. dont feel any worse. So with that said, I have two nice sets of T-Bars 4400 & 4800 that make good yard ornaments!

I will say this, and I may have already but I also did Billsteins and I've never been a believer in shocks helping ride quality but so much but I am a FIRM believer in these! Maybe they play a role in things.

If anyone ever wants to try this experiment that has more time than I I'm happy to work a deal on the T-bars but for now they're not in my way either.

 

[N2BRK]

I think that you are better off anyway. In the past I have spent a lot of time with motorcycle suspension, and less preload on a larger spring always seemed to work better for me. A spring with less rate and needing more preload didn't have as much left in to offer when cycling up and down before being overwhelmed and giving poor results..

 

[Chevy1925]

I think that you are better off anyway. In the past I have spent a lot of time with motorcycle suspension, and less preload on a larger spring always seemed to work better for me. A spring with less rate and needing more preload didn't have as much left in to offer when cycling up and down before being overwhelmed and giving poor results..

thats true to a point. you have a range to be in before spring rate is too much or too little. ideally on a coilover spring, you want 0-2" of preload in a spring to reach desired ride height. more than 2", spring is too soft. less than 0 (and yes you can go less than 0), spring is too stiff. if you have the preload correct but you still blow through suspension or it just rides bad, that is a valving issue.

on a torsion bar truck, this is harder to set right as its not as common for "preload range" and each mfg is different. i would bet the 5200lbs he has would have been the better bar at the end of the day as he is adding more preload to the bar to get the desired ride height. the ligher bar would require even more preload in relation to the 5200lbs bar and may not have gotten to desired ride height but im not there to know what inital preload was and blah blah blah. it would have been interesting to see the results though as its all based on mathmatics/theory until its proven. the test above would have been good ball park figures.