Ok, like I said...I wasn't trying to flame you. But this is often one of the most misunderstood topics.......and I was trying to keep more misinformation from being spread. You got the right concept......just totally backwards!! And again, I'm not trying to give you a hard time about it. I can tell you've obviously thought about it.......but you've probably thought about it too much!! You need to think about it in simpler terms.

Ok, it's late and I don't have time to go into much detail....but here's the basics:

First: A torsion bar is a straight coil spring. And, just like a coil spring, there is no way to make it stiffer.

Second: The "pressure" on the bar is caused by the weight of the truck. And the weight of the truck is always the same....no matter the height.

So, here's what we've got to work with:
The weight of the truck is what twists the bars.
The "spring rate" of the torsion bar determines how much the bar will twist before it supports the truck's weight.
Soooooo.....since the weight of the truck can't change.....and the spring rate can't change......there is no way that the "pressure" on the torsion bar can change.

Are you still with me? So, I guess now you're wondering........ since the "pressure" on the torsion bars is always the same........what determines ride height??
Well, it's the same principal as putting a block underneath your leaf spring. No matter if it's a 2 inch block or a 6 inch block, the "pressure" on that block is always the same. But, on the front.....this "block" is threaded and has a bolt head on it.

When you turn that adjustment screw, all you are doing is putting a taller "block" between torsion key and the cross-member.

Well, it's after 4am and I gotta get some sleep. You brought up a lot of good points....such as the ride being worse and the suspension not moving much when you put a jack underneath it. You are correct about that, but the reason isn't exactly the torsion bars. I'll explain later.....but first I want you to think about this:

You said....... "Basicly the torsion bars are trying to un-twist their "spring pressure" at the front a-arm downward thus creating the lift."
......this is an example of having the correct principal - just totally backwards. The torsion bars are not pushing the a-arm down. The twisting force is not created at the torsion key. Basically, the way you're thinking assumes the torsion bars have energy....that they are creating lift. But they are just a piece of steel. The energy is from gravity. So you have to start with gravity. Gravity wants to push the truck down, which means the control arm wants to go up. The torsion key will not move. The torsion bar is caught in the middle. The torsion bar's ability to RESIST twisting.....not it's ability to "un-twist" is what supports the weight of the truck.

With this in mind....I want you to think about what you said about the jack, and lack of up-travel......and see if you can come up with an answer. I'll be back later.

 

ok... I think I understand that, makes sense.

ok, but then why would a "re-indexed" torsion bar key change the ride height(I do understand the correlation between the key's index and the adjuster bolt and realize that they do the same thing, just compound on eachother). But when adding this "block" the torsion bars location doesn't change, still somes through the same hole in the crossmemmber, not 2"-6" lower.

So are you saying that the bar isn't twisting at all, that it just pushes the truck up (not the a-arm down, ) and the bar still basicly remains, un-twisted with no "pressure" other than just holding the weight of the truck, same as it was doing before cranking the bolt?


So does the truck still have just as much travel as it had stock? I can see how it would have less "down travel" as we just flexed the a-arm down at ride height thus creating less "down travel"(assuming there is a max travel measurement from stock, as i know there is, you know what i mean). But so from what I understand from what you are saying the "up travel" measurement(from ride height of course) should be just as much as it was stock. So why, if there is any less, whould there be a lack of "up travel"?


I would really like to thank you for taking the time to explain this to me and making sure that I, along with anyone else who reads this thread, truely walks away with no questions. I am very mechanical and I had I guess just seen the suspension design and created my own reasoning as to how it worked, so I appreciate you telling me how it actually does.

Anyway, the above are the last of the things i dont understand i think, for a few minutes anyway.

,
SouthernStyle

 

You're on the right track, and that's good!!

When I said it's the same as adding a block, I was referring to the adjuster bolt itself. The bolt is basically a threaded block. It increases the distance from the EDGE of the KEY to the piece the bolt threads into. The actual vertical location of the bar makes no difference. The only reason that the torsion bars are dropped with a lift kit is because the bar must exit the lower control arm in a straight line. And when you drop the lower control arm, the torsion bar must go with it. But the adjuster bolt can only move so far before it runs out of threads. Putting in an aftermarket key is basically like adding a spacer to the end of the bolt.

You're right, the bar IS twisting. However, you have to realize where the source of the twist is coming from. The bar is actually trying to RESIST being twisted....it's RESISTING the force of gravity trying to push the truck down. It's not twisting on it's own and trying to push the truck up. That would mean that the bar has it's own source of energy. But like all steel springs, they only store energy. When the truck is sitting still, the energy comes from gravity. And since gravity is always the same, the energy in the bar is always the same.

An air bag is different. Air bags store energy from an air compressor. When you raise the height on a truck with air bags....you ARE increasing the pressure. This is because you ARE adding energy.....from an air compressor.

Now this is all just in general terms. As the suspension moves, the angles change.....and the amount force that the bar "sees" changes. Within +/- 1 inch of ride height, the difference is negligible. But as you get higher and lower, things are gonna change. However.....the change may not be what you would think.


The more you crank your bars, the greater the angle becomes on your lower control arms. This makes it easier for the torsion bars to resist the force of gravity. So, in an extreme case.....the pressure on a cranked bar would actually be LESS than the pressure on a truck that had been lowered slightly.

Think of an Olympic gymnast on the rings. The most difficult thing is to support your body weight with your arms straight out. It's easier to hold yourself up with your arms angled down. Well, your lower control arms work the same way. It's harder for gravity to push the truck down when the control arms are angled down. So......less energy gets transferred to the bars. What this means is: If you could measure the twisting force being applied to the bar, a cranked bar would have LESS force than a normal bar.

Now, here is where the whole thinking backwards thing comes into play again. We've established that the more you crank a bar, the easier it is for the bar to resist gravity. And if it's easier for the bar to resist gravity....what else would the bar want to resist??
BUMPS!!
The suspension seems stiffer, not because the torsion bars have gotten stiffer.....but because they don't have to work as hard.


Now this example was only for an EXTREME condition. You would have to install aftermarket keys and crank them up for like 3 inches of lift to get that effect. For the most part.....when you stay within the range of the stock adjusters, the geometry doesn't change that much. But, it does effect your suspension travel.....which is what causes the most notable change in ride quality.

I don't have time to get into the whole travel thing right now. But I just wanna add one more thing to confuse you LOL!!

You can't change the stiffness of the torsion bar. But you can change the suspension geometry. If something changes enough to make the suspension feel stiffer, it's because the torsion bar isn't having to work as hard. If something changes, and the ride feels softer.....it's because the bar is having to work harder. So you could almost say: Any increase in ride stiffness means that the pressure on the torsion bar must have decreased.


I'll try to get to the whole shock and suspension travel thing a little later.......

 

WHEEEEEEEEEW, this stuff is a mess. I sure do appreciate you takin the time to explain all this to me, I think i'm starting to figure it out, as best as I can.

Sure am glad I have coil-overs though, definitely know how those work

 

hate to bring back a older thread, but which body style/year of chevy keys will fit on my f150? i have a guy with a 98 z71 that wants to trade, and i just want to verify if they will fit or not.

 

bump

 

????

 

lol ill give you a free bump eric

im pretty sure that 97 and 98 silverado lift kits are the same...which should mean that their suspension is the same, and this guy was going to put 97s on his...idk lol lmk if you need help doing the swap tho

 

one of garrett's friends has the chevy and wants to trade and yeah. i think we'll swap it out whenever we can confirm they are the right ones.
when you goin to make it out to one of the friday meets in spring-cypress?