Question about torsion bar adjustment

[Mineallmine]

I have been reading on torsion bar adjustment and have been finding conflicting answers on one part that I am trying to understand.

A lot of people say when adjusting ride height make sure to loosen the front nut on the lower control arm pin. I can't see why this is necessary. When you are adjusting the ride height the torsion bar (and pin) aren't actually being turned. When I had it apart the torsion bar moves directly with the pin, loose in the control arm, only stopping when it hits the adjustment bolt. I fully get not tightening the nut until the weight of the car is on the suspension as that's when the torsion bar is loaded up. If you adjust the lower control arm up or down, you are only moving the lower control arm, not the torsion bar itself. The amount of load on the torsion bar is exactly the same.

I do also get that it will require an alignment after as it will change the camber.

Just trying to clarify what I understand and have researched. You aren't actually changing the load on the torsion bar, just where the load starts being applied, thus the car will have the same load no matter what, just the control arm itself will sit either higher or lower due to it contacting the torsion bar arm (where the adjustment bolt contacts) earlier or later depending on if you are raising or lowering.

If there's something I'm missing please let me know.

 

[4mulas]

you Have too. Otherwise you risk ripping the bushing out of It.

look at it again, you’ll figure it out

and it’s not ‘many people say’. It IS the service manual says to do it.

 

[mopowers]

I guess some folks would say loosen the LCA pivot when adjusting the torsion bar, then tighten it back up when you have them where you want them because you want the LCA bushing to be at it's 'neutral' position at ride height. I question whether loosening up the LCA pivot nut would even allow the pivot pin to spin in it's bore with a minor torsion bar adjustment. Those pins are pretty tight once snugged up. You'd probably have to loosen the nut and bang it back out to even allow it to rotate with a minor torsion bar adjustment.

 

[Mineallmine]

you Have too. Otherwise you risk ripping the bushing out of It.

look at it again, you’ll figure it out

and it’s not ‘many people say’. It IS the service manual says to do it.

I was looking at it. If you tighten or loosen that adjusting bolt, the lower control arm moves up or down. The torsion bar doesn't move, thus the bushing doesn't move. At least that's what I can see. I will have to have another look at it today and again at my service manual. I didn't see in it to loosen that nut when adjusting the lower control arm, only when replacing the bushing and not to tighten it until the weight of the car was on it.

Sorry if I'm missing something. Thanks for the reply

 

[Mineallmine]

I guess some folks would say loosen the LCA pivot when adjusting the torsion bar, then tighten it back up when you have them where you want them because you want the LCA bushing to be at it's 'neutral' position at ride height. I question whether loosening up the LCA pivot nut would even allow the pivot pin to spin in it's bore with a minor torsion bar adjustment. Those pins are pretty tight once snugged up. You'd probably have to loosen the nut and bang it back out to even allow it to rotate with a minor torsion bar adjustment.

I fully agree with this to the effect that it wouldn't turn if not knocked free. But again, I don't quite understand how it would move with raising or lowering the control arm. The load is the same either way. You are just changing where the control arm stop. Maybe I am missing something here, but that's how I understand the operation of the setup when I look at it.

Loosening it doesn't hurt anything, I just don't see the benefit or requirement.

Thanks

 

[4mulas]

I fully agree with this to the effect that it wouldn't turn if not knocked free. But again, I don't quite understand how it would move with raising or lowering the control arm. The load is the same either way. You are just changing where the control arm stop. Maybe I am missing something here, but that's how I understand the operation of the setup when I look at it.

Loosening it doesn't hurt anything, I just don't see the benefit or requirement.

Thanks

the bushing gets pressed into the control arm which has the adjuster lever on it. The pivot shaft the gets pressed into the bushing inner hole. If you install the arm, tighten the pivot shaft tight to the k frame which is stationary, then do a whole bunch of adjustment on the height adjuster lever via the bolt you turn you are twisting the heck out of the rubber in the bushing, between the control arm and the pivot shaft. The pivot shaft isn’t moving, but the control arm is.

if doing a minor adjustment it’s not as important as when doing a major adjustment.

this is all in the Chrysler service manuals particular to your car. So either you’re right and all those Chrysler engineers are wrong, or you need to just really look at how these work in several schematics that are available online even to get your head around It.

good luck

 

[72bluNblu]

I fully agree with this to the effect that it wouldn't turn if not knocked free. But again, I don't quite understand how it would move with raising or lowering the control arm. The load is the same either way. You are just changing where the control arm stop. Maybe I am missing something here, but that's how I understand the operation of the setup when I look at it.

Loosening it doesn't hurt anything, I just don't see the benefit or requirement.

Thanks

It’s the lower control arm bushing that’s the issue. Nothing in that assembly spins, so when the control arm moves up and down the bushing has to flex. If you force the rubber to flex too far, it will tear. That’s why in the FSM when you install the lower control arms you leave the pivot nut loose until the car is at ride height - half the flex in the bushing is for travel on compression, half is for extension.

If you significantly change the ride height without loosening and re-tightening the pivot pin/nut, the bushing will already be flexed at ride height, and in the “long” direction (because you’re not in the middle of the range of travel) you risk tearing the bushing.

 

[Mineallmine]

When I installed my new pin and bushing into my LCA, I was able to pivot them independently of the LCA. It would pivot until it hit the adjustment bolt. The torsion bar mounting point and bushing/pin are one, and the LCA is actually separate (in a manner of speaking) right?

If You take the load off the torsion bar, and then proceed to remove the shock bolt and lower ball joint, does the LCA not have the ability to drop straight down? The torsion bar does not move with it. Or am I forgetting something.

Not trying to cause an argument or anything, just trying to cement my understanding of the operation. I really appreciate the responses.

Also, I just looked at the 66 service manual (don't have my 63 manual here) and it makes no mention at all of loosening the pivot nut. Just to make sure you jounce the car up and down numerous times after each adjustment to determine height.

 

[72bluNblu]

Do you have rubber LCA bushings? Or poly or Delrin?

The LCA will rotate around the torsion bar socket freely if the adjuster plate and bolt aren’t in place, that’s normal. But when the adjusting bolt is in contact with the adjusting lever and socket, the control arm, adjusting lever and socket, and the torsion bar all move as one unit (that’s how it works when loaded). Assuming you have rubber LCA bushings, the pivot pin is pressed into the bushing which is pressed into the torsion bar socket. The pin does not rotate. The socket rotates with the control arm when the suspension is loaded. The bushing has to flex.

You are correct in that when you adjust the bolt to change the ride height the socket and torsion bar do not move, you’re just changing the angle of the control arm. But you’ve changed the position of the control arm within the range of travel, so the bushing is not neutral in the middle of the range.If it goes too far in one direction, it will tear.

 

[Mineallmine]

But the bushing moves with the torsion bar, not the control arm, correct? When you loosen or tighten the bolt the bushing isn't turning, nor is the torsion bar. Only the LCA is.

I know it all moves as one assembly once adjusted. but the change is the relation of the control arm to the bushing and torsion bar. You don't turn the bushing at all when you are loosening or tightening the bolt.

Otherwise, when I release the ball joint without loosening the pin nut, I shouldn't be able to push the LCA down without the bushing turning. IIRC I thought the only thing keeping you from pivoting the LCA down after release was the strut rod

 

[72bluNblu]

But the bushing moves with the torsion bar, not the control arm, correct? When you loosen or tighten the bolt the bushing isn't turning, nor is the torsion bar. Only the LCA is.

I know it all moves as one assembly once adjusted. but the change is the relation of the control arm to the bushing and torsion bar. You don't turn the bushing at all when you are loosening or tightening the bolt.

Otherwise, when I release the ball joint without loosening the pin nut, I shouldn't be able to push the LCA down without the bushing turning. IIRC I thought the only thing keeping you from pivoting the LCA down after release was the strut rod

The bushing rotates when the torsion bar socket rotates. The socket twists the torsion bar. The socket is connected to the adjusting lever.

The control arm can only move independently of the adjusting lever and socket if the adjusting bolt isn’t in contact with the lever- when the control arm is unloaded.

In your example, if the adjusting plate and bolt are held in place, the resistance of the bushing will hold the LCA up. If the control arm falls down in that scenario, it’s because the adjuster isn’t loaded. Which, by the way, it should be within the normal range of suspension travel. The adjusting bolt should have some tension on it if the control arm is between the bump stops, otherwise you risk the adjuster becoming unseated when you fully extend the suspension.

You are correct in that the bushing is not turning when you’re adjusting the bolt. But you have moved the resting position of the control within the range of travel, the LCA is no longer in the middle. You need neutral for the bushing to be in the middle of the range of travel, otherwise you will flex the bushing too far in the “long” direction.

 

[Mineallmine]

I have one more question. I am going to have to go over it all again once I get home to see what I'm missing because I must be missing something and that is definitely possible

As long as the amount of load that is placed on the front suspension of the car has not changed, the amount of load on the torsion bar hasn't changed, thus the bushing will turn no more or less regardless of the position of the torsion bar position (adjustment). So after adjustment it's center will be the same under load, just the relative position between it and the adjusting lever will be different. The position of the adjusting lever will never move from where it is, correct? If so, the bushing will not have moved. Just the amount of thread sticking out of the adjusting bolt that is pushing on it. (whether more or less, depending on raise or lower)

Sorry if I'm not explaining myself correctly. I might be completely off here.

 

[72bluNblu]

I think you’re explaining yourself correctly, you’re just completely ignoring the distance the LCA will travel from its new position. That distance is the problem.

Also, the load on the torsion bar does actually change depending on the position of the control arm. The weight of the car remains the same of course, but the load on the torsion bar changes with the effective length of the control arm. When the control arm is parallel to the ground, the length of the control arm and the effective length are basically the same. But when the control arm is at an angle, the horizontal distance from the ball joint determines the effective length. So, raising/lowering the car can actually change the load on the torsion bar at ride height, you’re changing the effective length of the control arm.

The procedure for installing the LCA is very clear in the factory service manual. The LCA pivot nut is supposed to be torqued at ride height. That makes the whole procedure more difficult. There is absolutely a reason for it, it’s not just that a bunch of us on the internet got together and misunderstood how the suspension works and came up with our own procedure. The procedure is in the FSM.

 

[Mineallmine]

I'm not saying anyone got together and misunderstood anything. Like I said I'm not trying to start an argument. The FSM does not say to loosen the pivot nut (for the 66 Manual anyway) for adjusting ride height. To torque after reinstalling the LCA, absolutely, and I fully agree with tightening with load on the suspension.

I didn't start this thread to try and say I'm right, you are wrong. I just was trying to determine the correct way and reasons. Loosening it, doesn't hurt anything during the process, obviously, but I wanted to understand it better. I have found posts on here and other sites saying you don't have to as well. Just wanting to see if it really matters.

I added the 66 FSM procedure for reference.

 

[Phreakish]

The weight of the car remains the same of course, but the load on the torsion bar changes with the effective length of the control arm. When the control arm is parallel to the ground, the length of the control arm and the effective length are basically the same. But when the control arm is at an angle, the horizontal distance from the ball joint determines the effective length.

I think this is the crux of the matter.
Changing only the ride height at the adjuster doesn't rotate the torsion bar, but the torsion bar does rotate as a result of changing the ride height due to the other changes in the geometry caused by the ride height change. Rubber bushings are pretty limited in their deflection range, and so maximizing it is essential to a long service life.

 

[4mulas]

I think this is the crux of the matter.
Changing only the ride height at the adjuster doesn't rotate the torsion bar, but the torsion bar does rotate as a result of changing the ride height due to the other changes in the geometry caused by the ride height change. Rubber bushings are pretty limited in their deflection range, and so maximizing it is essential to a long service life.

It doesn’t rotate the bar but it twists it. This is what creates the spring to act as your suspension

 

[Phreakish]

It doesn’t rotate the bar but it twists it. This is what creates the spring to act as your suspension

That's what I meant. The adjustment doesn't directly twist the bar more, but it does wind up twisting differently as a result of the change in the angle of the control arm. In my experience, moving the adjuster changes the at-rest amount of twist in the bar.

 

[RustyRatRod]

I think as long as you're adjusting within the range of the factory specs, loosening the pivot nut isn't required. But as @72bluNblu recommended, if you go much out of that range then you probably should loosen it. Of course if you have poly or delrin bushings, then it does not matter.

 

[72bluNblu]

I'm not saying anyone got together and misunderstood anything. Like I said I'm not trying to start an argument. The FSM does not say to loosen the pivot nut (for the 66 Manual anyway) for adjusting ride height. To torque after reinstalling the LCA, absolutely, and I fully agree with tightening with load on the suspension.

I didn't start this thread to try and say I'm right, you are wrong. I just was trying to determine the correct way and reasons. Loosening it, doesn't hurt anything during the process, obviously, but I wanted to understand it better. I have found posts on here and other sites saying you don't have to as well. Just wanting to see if it really matters.

I added the 66 FSM procedure for reference.

View attachment 1716091770

View attachment 1716091771

Right, but you have to understand the the FSM is always telling you to adjust the ride height to the same spec. Which means if you followed the FSM the whole way through and you tightened the pivot nut at ride height when the LCA was installed, if you should ever need to adjust the ride height you'd be adjusting it back to where it was originally. Not setting a completely new ride height.

So as RustyRatRod said, if you're within the factory specs you're fine. If you're substantially changing the ride height, you will likely be changing the effective length of the LCA enough that you will have a loaded bushing at your new ride height because the load on the torsion bar will be different. You may also be moving the LCA far enough from center of range that you're changing the distance in one direction of travel enough to over stress the bushing. Ie, if you lowered the car, your suspension will travel further on extension than it will on compression, unless you have also adjusted the height of the bump stops to keep the travel distances equal.

Loosening and re-torquing the pivot pins is a pretty simple operation that only takes a few minutes. If you don't think it does anything, or you don't think you're changing the ride height enough for it to matter, don't do it. Personally in that situation I'd rather take the few extra minutes to loosen and re-torque them and have the peace of mind that it can't be an issue, than not do it and discover later than I changed the height enough to tear the bushings. But I use Delrin bushings on my cars so as to eliminate both the slop and the resistance to travel that the rubber bushings have, so, the entire point is moot for me.

 

[Mineallmine]

Right, but you have to understand the the FSM is always telling you to adjust the ride height to the same spec. Which means if you followed the FSM the whole way through and you tightened the pivot nut at ride height when the LCA was installed, if you should ever need to adjust the ride height you'd be adjusting it back to where it was originally. Not setting a completely new ride height.

So as RustyRatRod said, if you're within the factory specs you're fine. If you're substantially changing the ride height, you will likely be changing the effective length of the LCA enough that you will have a loaded bushing at your new ride height because the load on the torsion bar will be different. You may also be moving the LCA far enough from center of range that you're changing the distance in one direction of travel enough to over stress the bushing. Ie, if you lowered the car, your suspension will travel further on extension than it will on compression, unless you have also adjusted the height of the bump stops to keep the travel distances equal.

Loosening and re-torquing the pivot pins is a pretty simple operation that only takes a few minutes. If you don't think it does anything, or you don't think you're changing the ride height enough for it to matter, don't do it. Personally in that situation I'd rather take the few extra minutes to loosen and re-torque them and have the peace of mind that it can't be an issue, than not do it and discover later than I changed the height enough to tear the bushings. But I use Delrin bushings on my cars so as to eliminate both the slop and the resistance to travel that the rubber bushings have, so, the entire point is moot for me.

So, I did the adjustment to my ride height over the weekend. I found the front was half an inch higher than the rear. I dropped the front one inch. Looks much better now.

I did loosen the pivot shaft nut doing this as suggested and tapped them to make sure they broke free. I may not totally see how it could move but as I said, I don't know everything, and as stated it is easy to do, so I erred on the side of caution. I had previously marked them when I was removing them and after the adjustment did not notice any change, but again, it could be so small I possibly wouldn't notice any way.

I do appreciate all the input received on this. Definitely was not trying to start arguments over this topic. I just saw conflicting answers on this forum and others and was looking for clarification. It great to have a place like this that you can put up questions and discuss what and why and how. My car may be done (for now...they never really are done are they?), but I will be back with more questions as issues come up with the shakedown runs, and even after I'm sure.

Thanks again.

 

[72bluNblu]

Was the 1" lowering because the car was higher than stock?

If you're 1" lower than what the factory height setting says, then factory torsion bars will result in the suspension bottoming out all the time, even under normal conditions. Lowering the car that much means you need to increase the wheel rate. Which is fine, since these cars were so under sprung. You may also need to look into running a shorter lower bump stop to bring back some suspension travel.

If you lowered the car 1" from where it was, you will also need a new wheel alignment. That's more than enough drop to mess with the alignment settings to the point that they can cause problems.

 

[Mineallmine]

Drove it a bit already and no bottoming out issues so far. Had the alignment done yesterday