"Dewayne, I measured the distance from the rubber stop to the lower A arm as promised. It comes out to 2.4 inches with the truck at normal stance. Is this distance in the acceptable ranage you were talking about?"


Range for best handling is .75 to 1.0 inches. That's on the donors car. That is a bit below factory preload. My best guesstimation is factory intended height is in the 1.25 to 1.50. Now that is inboard from the wheel. It sounds like you have really got the T-bars cranked. But before I jump to conclusions, can you give me your tire diameter and height to the lower bumper. I could then tell with some accuracy. It really sounds like front wheel and tire time to me John. Extreme cranking or torsion bars is going to make something bad happen someday. Maybe some more measurements will indicate you aren't as ovetightened as I suspect.


I took some pix also with the wheel removed and a jack holding the A arm at normal elevation. I will post them later.

Good, email it to me if nothing else.

I have a need for a clarification:

"You said "He takes the slack out of suspension and then tightens the bars up just a couple more inches of lift." This is confusing to me. Isn't the torsion bar at constant tension no matter what the elevation is?"

You have hardware slack for so many turns. Don't worry about it if it's confusing you. Not that important. Yes, a T-bar is a constant rate spring. If you go way looser or tighter than stock, it starts acting in a way that doesn't make a lot of sense to me.


"When we alter the position of the torsion bar, does the rating of the bar not remain the same? I thought that the difference we sometimes report after changing the ride height was due to the fact that we are altering the configuration of the bars. I can understand the ride changing if the angle of effect on the torsion is changed. It seems to me that the closer the t-bar is to parrallel with the ground, the better (softer) it will perform. Does this make any since?"

No, not at all unfortunately. You just described how a progressive rate spring should act. I know you are confused. Don't feel lonely. I've asked everybody except Carroll Shelby and Lee Iacocca. I don't have anything that resembles a logical explanation. They try, and then they end up telling me it is actually a progressive rate spring. I can't find anybody I trust to state a T-bar is a progressive rate spring. I even asked Jeeves. And Jeeves is damn near as smart as George and AX But I can find a long line of folks who will tell you they feel VERY soft until you approach the correct preload. I'm inclined to believe it has something to do with the changed geometry on the low end of adjustment. You may be approaching the yield point of your T-bars. I can understand why they would tighten up if you overtighten them.

I know this is a long thread, but it is starting to sink in. Thanks, John

Well that's great to hear. As soon as I get everything clear in your mind. Please repeat it back to me and maybe I'll understand it too.

For now, lets just concentrate on whether you're flirting with busting a T-bar or not. I've had that happen on a longitudinal T-bar car before. And its hard to concentrate on steering when one side of the vehicle suddenly drops 6 or 8 inches. And BTW, that was a blatent attempt to scare you into taking this seriously. I'd be really sad if you flipped your truck. Oops, there I go again.

 

Sorry, don't mean to change the thread,just one question.
I've been following this thread, to see if I can pick up any info for down the road with my cordoba IFS.(Longitudinal)
Dewayne, I read of the misshap with these t-bars, is this a common problem, or was it due to improper adjustment.
Mike

 

The main thing that will make a t-bar snap is deep scratchs and/or nicks. These become stress points. Like cutting the edge of a rubber band. Once it is streched, that cut will continue through the body until it snaps.

Some people try to use vise-grips and a hammer to remove longitudinal torsion bars. This is not correct and WILL result in broken bars. There is a tool for removing them, but you can use 2 pieces of 2x4 to sandwich the bar a them use a deadblow mallet against the wood to force them out. FYI, may sure the lock ring is out and the adjuster is backed off all the way.

Scratchs hurt all types of torsion bars. Be careful with them.

 

I can only offer an opinion. No, I don't consider it to come anywhere near meeting the definition of common. I would fathom a guess they break far less often than coil springs. I've sure changed a lot of broken coils and leaves. Only a few T-bars. There are exceptions, but a broken coil still usually leaves you with half a spring when it collapses on itself. So does a broken leaf. Broken T-bar, you're completely out of suspension on one corner right now buddy. I't surely happens, but I have never even seen a single broken Volare style bar. I have only personally snapped one longitudinal T-bar. (Only owned one car with them). It tried to come through the floor of my Challenger and gave me a little tap on the foot. No harm, just scared me good. Bumper was about throwing sparks. I imagine Chrysler calculates it out so you won't likely plant a bumper in the street. Just a hunch, but I'm doubting they did any Volare in an Effie T-bar failure testing. I'm not planning on conducting any either.

 

Thanks for the info guys, I'll surely keep it in mind for future reference.
Mike

 

Ok Dewayne, I measured the wheel and bumper heights for comparison. They are 26.5" and 10" respectively. The bumper measurement was from the bottom edge to the floor. Now a question about catastrophic failure.

If my Dodge Aspen torsion bars are adjusted all the way up and then all the way down, wouldn't the weight pressing down on them be the same? Does it not take the same amount of strength to hold the truck's weight in both configurations?

I am having trouble understanding why they might break because of being adjusted toward the top of the range. In my mind's eye, they are just a long piece of metal shaped like a "C".

Kind of like [_ .

And when the adjustable short end is elevated, it elevates the other end and vise versa when the short end is adjusted lower. I think I'm getting hung up on the terminology of "slack, looser, and tighter".

I've never heard of one of these torsion bars braking until this thread. So you can understand why I'm surprised and worried.

I'm posting pix in my gallery. Thanks, John

PS: Sorry, I tried to make a new album, but for some reason am unable to make it stay. So, I put them in the 54 album.

 

I'm sure FF will provide more info, but my take on your question is yes, the load is the same the problem comes when you approach the elastic limits of the bar, by say lifting up too heavy a weight for the bar by cranking up the adjuster putting more twist in the bar than CP designed it to carry at rest. Now when you hit a bump you can overstress the bar resulting in a loud BANG! I too had a longitudinal TB break but while the car was sitting still (fortunately).

 

No AX, ‘fenders is just going to add more questions rather than answers again.

John,

I will check your measurements against mine to see how far apart we are. Will it truly prove anything? Not certain yet. But I think I am getting somewhere finally. I have some info from GM (they use T-bars on their trucks). I am going to have to get some of the engineers to help me. I have to scan to JPGs and email to George, AX or whomever else wants a crack at this.

I think I am tracking your logic? Do you believe that once your truck starts to rise, any further turning of the adjuster merely relocates the spring, rather than induce any further twist in the T-bar? Because your truck weighs 3500 pounds, whether the bumper is 8 inches or 14 inches off the ground? I believe this is very close to an accurate statement, but I believe the bar twists just a bit more as you go radically higher. (Not because the bar is progressive. My GM literature makes it sound less like fenderbabble. The total twisting range on a T-bar isn’t that large. (I’ll be paint marking mine next time I release tension on mine for whatever reason). It wouldn;t be hard to verify or disprove. A minor change could get you close to the edge of the operational range perhaps?

I’ve been commenting that I think it has to do with geometry of the lower control arms (LCA), but it’s not explained by bottoming out because I am nowhere near doing that. I have finally found some literature that sounds intelligent. It is from GM (they use T-bars on their trucks). The premise of the piece is that you DO affect your ride quality when you jack with your T-bar adjustment, but it’s not due to spring rate change, because a T-bar is not a progressive spring. The article is trying to kill the urban legend a T-bar is progressive, while explaining to truckers why their ride stinks after they lift the truck up an extra inch.

There are a couple more things we have to understand about T-bars I can’t explain. I also have a piece from some sort of Physics/Engineering journal. Two pages I could never possibly comprehend. The last sentence reads……………

“Presetting thus increases the torque capacity of a bar by decreasing the stresses in the highly stressed outer skin, whilst compensating by an increase of stress level in the highly loaded core.”

Yeah whatever, sounds like Egghead doubletalk to me. LOL

I think this is may be relevant to the discussion. It may offer the reason for proper T-bar preload adjustment. I keep reading in automotive manuals that preload must be correct, for proper operation of a T-bar. But an explanation is never offered. And if they are misusing the term preload in the manuals, it might not matter. We’ll see with some help from the guys.

Also, it’s not like your T-bar is riding on precision lubed bearings. When the bar angle is being radically changed, it’s riding at strange angles as it enters and leaves the stiff rubber mounts. These mounts are pretty substantial. Our T-bar style has double the friction points of a standard bar. We may be inducing some additional friction (or bind) at the LCA when we stray far from stock control arm geometry. A lot no, but it may add to the problem.

You and precious few others say they have a stiff Volare ride. Everybody else is complaining it’s too soft. We have the same drivetrain weight and identical spring rate (minus fatigue differences). There is an explanation for this. We'll get it.

 

OK here's what I believe you are experiencing: angular displacement. (I gave a clue back in the R&H but no one took me up on it)
Your lower control arm is designed to be horizontal at rest. It has a pivot point, so it's movement is angular rather than linear. The bumps are linear (perpendicular to the road surface). As you get further from horizontal at rest the smaller the angle the control arm pivots thru for the same amount of vertical displacement, so the torsion bar is twisting less thus feels "softer". Does anyone follow me?

 

AX

Yes I do follow you. It's the point of the GM article I have. I tcurrently think it's a factor in all this. I just got the documents scanned and will email them in a moment. I did catch your mention of it on the suspension thread. It got tangled up with a statement that we are bottoming out on our bumpstops too. That part isn't true. Nor important as long as you trust that is not part of the equation. It's not a factor until you go VERY radical up or down on the preload adjustment.

We have several issues to resolve to truly understand this IFS. And it doesn't all have to happen tonight. The right answer is a lot better than a quick one. After looking at my DOCs.

1. What does preload really mean? How does a T-bar become stronger when preloaded. What does stronger mean?

2. Is John truly in danger of popping a T-bar, or am I scaring the poor man for nothing? I am going to the garage now to check his measurements against my truck to see where he is in relation to mine. Which rides on the exact opposite of the soft-harsh curve.

 

Wow Ax, I actually followed that! It took 4 fingers and both thumbs but I see what you mean. Unfortunately, I have to call into play some more of my sometimes frustrating logic. Let's say that the lower control arm being level is the optimum position just for the sake of discussion. You are saying that a truck with a lowered stance would have a lower control arm that is angled at say 10 degrees and that makes for a "soft ride." If your theory is right, then would not the same truck readjusted the opposite to 10 degrees higher than the original optimum also "soft ride." If you catch my drift, then the further from horizontal, the softer the ride. So then my "high setting" should be just as soft as a similar truck with the opposite orientation just as a "low setting". This sounds like I am being sarcastic, but I'm not. I'm just trying to get this down in writing before the fog comes back in.

PS: I am more inclined to go along with your angular theory if you apply it to the angle of the torsion bar itself where it attaches to the control arm. OOPS here comes the fog.....

Fenders, I had a thought about what you said in regard to torsion bars breaking. Perhaps it's all relative to that distance between the lower control arm and the rubber stop. The bigger that space is, then the more the torsion bar could twist during a serious impact in a pot hole for instance. High setting, more twist possible, which means more stress on the torsion bar. Low setting, less twist possible before "bottoming out", thus less stress on the torsion bar. Does this make any sense? Because I'm thinking that this makes for a reasonable explaination. If not, (in my best Rosana Rosanadana voice) NEVER MIINNND. John

 

John

We'll get back to the more complicated subject soon enough. Here's some general info for now. You are correct, just use the distance from the bumper to the LCA. It eliminates most all variables. First, my jounce bumper is 1 1/2" tall. That matters from purpose of comparison. Call bumper exactly midway between the bushings and the wheel center for our purposes. (it's real close) So distance there times two = ride height/suspension travel out at the wheel.

My full extension is 3.6"

MAX compression would be zero before you begin crushing the bumper. So max wheel travel is 7.2 + bumper crush. We'll omit bumper crush from here on out.

At ride position you are at 2.4" between the bumper and LCA, which puts your ride height at 4.8" About 1.2 over midway. It's hard to judge when the control arms are level, but it's near the middle of the range.

Thanks to my new high pressure shocks, I am now at about 1.5. That's 3.0 at the wheel. So I bottom out at 3.0 travel, you at 4.8 travel. I am currently about 1/2 inch under preload on the low side. You are about 1 1/4 on the high side. My truck has been dangling the wheels tonight, so it will come down just a bit after I drive and settle the T-bar back in.

The Mopar guys like it around 1.0 at the bumper. 2.0 at the wheel. I'm guessing they are trading off a little control arm angle and suspension travel for some lower center of gravity.

Provided our lower jounce bumpers are the same, you aren't as drastically high as I originally thought. You may be off enough to cause the geometry problems. That remains to be seen. I'm more inclined to think you need to be looking hard at your T-bar bushing condition to explain your stiff ride. And the other routine stuff of course like tire pressure, bad shocks etc. How old are the T-bar bushings? At both ends. And yes I know what they cost.

And my new shocks mean I need a front end alignment.

 

Let's try this to see if it holds a martini: The majority of what we concern ourselves with in determining ride feel are bumps or other irregularities that cause an upward or jounce movement of the wheel. (when we hit a hole in the pavement we don't usually say "Boy this vehicle rides hard!", but rather it's "DMAN when they gonna fix that crater?", a difference in subjective judgement!) The greatest angular displacement per unit of vertical movement is when the control arm is horizontal where it approaches equality. If you raise your front end so the control arm is drooped at rest, then any movement upward is increasing in angular displacement as the control arm approaches horizontal thus twisting the torsion bar more until the control arm passes horizontal. The further you go from horizontal at rest the more pronounced that angular displacement effect is going to be noticed: harder riding in your case, softer feeling in Dewayne's.

 

AX

I do hope we are getting somewhere. That matches up to the GM article, which doesn't appear to contradict itself at any point. So that's two votes. I do have one question though. Read your last post where you discussed the load the T-bar effectively "sees". Did you say that backwards? If it sees less load, it actually deflects less. Would the ride not be firmer rather than softer. If you meant what you said, then I need the explanation expanded, without getting too technical.

 

can you quote the part you're asking about?