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  #16  
Old 04-17-2018, 01:02 AM
Diesel911's Avatar
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Quote:
Originally Posted by leathermang View Post
Then what is that straight bar running parallel with the center line of the car.. with the serious Bearings do ? Which used to be called a Control Rod...
This is what I know about it.
On a W123 Factory Service Manual the Sway Bar is called the Torsion Bar and the tip of that goes through the Upper Control Arm which if I remember correctly is what the original poster said the tip of is busted off. If that is the case the Upper Control Arm is on that side is going to wonder around a bit.

The other part that attacks to the Lower Control Arm and the rear of theFender well on the forum is typically called the Guide Rod. In the Manual it is listed as Supporting Joint and Supporting Tube of Brake Support.

So does the Control Rod you are speaking of attach to the upper or lower control arm.

33-540 in the manual is title checking and repairing the bearing of upper control arm.

That is the terminology I am used to.

Unfotunately different parts of the service manual sometimes call the same part by a different name. I don't no why but I think it is likely an issue of when the manual was traslated from German into English.

So where does the Control Rod you were speking of attach?

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  #17  
Old 04-17-2018, 09:16 AM
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Quote:
Originally Posted by Diesel911 View Post
This is what I know about it.
On a W123 Factory Service Manual the Sway Bar is called the Torsion Bar and the tip of that goes through the Upper Control Arm which if I remember correctly is what the original poster said the tip of is busted off. If that is the case the Upper Control Arm is on that side is going to wonder around a bit.

The other part that attacks to the Lower Control Arm and the rear of theFender well on the forum is typically called the Guide Rod. In the Manual it is listed as Supporting Joint and Supporting Tube of Brake Support.

So does the Control Rod you are speaking of attach to the upper or lower control arm.

33-540 in the manual is title checking and repairing the bearing of upper control arm.

That is the terminology I am used to.

Unfotunately different parts of the service manual sometimes call the same part by a different name. I don't no why but I think it is likely an issue of when the manual was traslated from German into English.

So where does the Control Rod you were speking of attach?
It IS true that terminology has changed on many items on cars.. which I try to point out not just in this case .. typically starting with the phrase ' in the old days ' ......and it is also true that the MB FSM suffers from not being written originally in American.

In the old days.... this part I am talking about was commonly called a ' Strut Rod ' and this url from google pictures represents it well... it is on the bottom of the front suspension and has substantial connection to the chassis at the back of the wheel well... and hard fastened to the bottom of the moving suspension supporting the wheels at the front. Notice there are TWO parts and at the end is a substantial bearing ... American cars and trucks ' of old ' typically only had that placed and held with large rubber grommets at the chassis.

Counter acting braking forces and the change in steering geometry due to bumps takes serious but flexible bearings... another reason seeing the simple bushings which hold the Sway Bar obviously does not provide....
AND you would not use a Spring to accomplish that function.....as shown by the rigid connection with serious bearings at the chassis. I am sorry I can not figure out how to post a picture of the photograph in the FSM.
As to the upper control arm wandering around.. you have two bushings on the lower control arm , one at the top PLUS this lower strut rod at the bottom.. .the ' sway bar ' is attached to the top.. but is not the controller of the physics .. it is made to reach that neutral spot in order to provide the Left-Right roll comparison/feedback/mitigation between the reaction of the car to trying to roll about its longitudinal center of gravity in corners.

https://www.google.com/search?q=strut+rod+definition&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwiygOPRrMHaAhUJRa0KHWiABS4QsAQIiwE&biw=766&bih=474
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  #18  
Old 04-17-2018, 12:21 PM
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Some men just can't be reached.

I don't need a picture. If you don't believe what 911 and I are saying about the sway bar controlling the upper control arm, go out to your car, take the bolt out of the end of the sway bar and see if you can move the whole front wheel forward and aft. Why do you think the sway bar is basically level from its mounting point at the firewall to the upper control arm? Its to be able to control the fore and aft of the upper control arm. The brake control rod does this for the lower control arm. It has to be this way when there is only one frame attach point for a control arm. If they were like a 70 Chevy, and had two frame attach points, you wouldn't need a sway bar to perform that function. And, you could put the sway bar in an easier to change place, like a 70 Chevy.

Last edited by resto108; 04-17-2018 at 12:32 PM.
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  #19  
Old 04-18-2018, 12:47 AM
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OK I found this attached pic in post #9
http://www.peachparts.com/shopforum/performance-paddock/342744-w123-racing-setup-serious-questions-within.html

While the picture shows the arrangement of a W123 suspension it is mounted on what appears to be a custom frame.

In the 2nd pic I drew arcs which is the direction the Sway Bar and the Guide Rod move when the go up and down. If you then look at the upper control arm you can see that Sway Bar's attachment to the Upper Control Arm means that the Sway Bar controls/restricts the directions that the Upper Control Arm can move.

Without the Sway Bar the Upper Control Arm can wonder in nearly any direction disturbing the alignment.
Attached Thumbnails
Torsion bar salvageable?-w123-front-suspension-b.jpg   Torsion bar salvageable?-w123-front-suspension-.jpg  
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Last edited by Diesel911; 04-18-2018 at 01:02 AM.
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  #20  
Old 04-18-2018, 10:52 AM
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I can't help you guys anymore than I have already.
You drew the parts movement lines in your picture wrong..
The hard attachment to the lower part of the suspension and the bearing at the end of the strut rod do not allow that movement you drew....It is also clear you did not read the references I supplied... or are not able to understand them.

What you should have drawn on the lower rod is what it does not allow to happen...
and that is fore-aft movement of the lower control arm. That with the other restrictions provided by bushings in various planes.... is what controls the movement of the place you are focused on...

Last edited by leathermang; 04-18-2018 at 11:14 AM.
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  #21  
Old 04-18-2018, 11:45 AM
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Quote:
Originally Posted by leathermang View Post
I can't help you guys anymore than I have already.
And we will certainly appreciate your continued forbearance.

To return to the OP's anticipated repair problem, let us note that the bar end repair kits do the job quite satisfactorily, and without removing the bar from the chassis.

Last edited by Frank Reiner; 04-18-2018 at 12:51 PM.
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  #22  
Old 04-18-2018, 12:10 PM
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Originally Posted by Frank Reiner View Post
And we will certainly appreciate your continued forbearance.

To return to the OP's anticipated repair problem, let us note that the bar end repair kits do the job quite satisfactorily.
The sad thing is that replacing the Sway Bar would not have had to be such a Task... as it could have been joined in the center.... made in two parts... with a good hefty sliding joint... Torsion bars when used as STRAIGHT Longitudinal springs in many Chrysler products had fittings on the end which were just fine...and allowed the riding height to be adjusted at the end.. the holding point...
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  #23  
Old 04-19-2018, 11:01 AM
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Originally Posted by resto108 View Post
Some men just can't be reached.

I don't need a picture. If you don't believe what 911 and I are saying about the sway bar controlling the upper control arm, go out to your car, take the bolt out of the end of the sway bar and see if you can move the whole front wheel forward and aft. Why do you think the sway bar is basically level from its mounting point at the firewall to the upper control arm? Its to be able to control the fore and aft of the upper control arm. The brake control rod does this for the lower control arm. It has to be this way when there is only one frame attach point for a control arm. If they were like a 70 Chevy, and had two frame attach points, you wouldn't need a sway bar to perform that function. And, you could put the sway bar in an easier to change place, like a 70 Chevy.
You only had that first sentence the other day and I assumed it referred to Diesell911.... since he had not understood the situation.

''' You don't need a Picture''' LOL I suggest you do need a picture because you are so young that you only have experience with the MB front suspension.... I took my first automotive mechanics class in about 1964....When were you born ? LOL

The MB engineers hooked the anti sway bar to the top of the spindle... and ignoring several other constraining pivot points... you and Diesell911 decided IT was there to position the upper part of the spindle...

That is an efficient system.. but not having seen other systems .. you attributed a function which when you look at the design of the other systems... many of which attach to the LOWER control arm or lower part of the spindle show that is not its function.

Here is a picture.... the first one in this reference... which shows the ''''Anti Roll bar Link Arm """" ..... which clearly are only going to function in an up and down plane... and are not even near the upper part of the spindle... obviously making the ' function ' you ascribe to them anti sway bar impossible.

https://pdfs.semanticscholar.org/2f2c/418f7042b5ea00288bdf0b359f3109ad0947.pdf
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  #24  
Old 04-19-2018, 09:12 PM
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Quote:
Originally Posted by leathermang View Post
While the sway bar helps ' locate' along with the two lower control arm bushings
Everyone does agree with you on this.

Quote:
Originally Posted by leathermang View Post
.... that does not mean it has any function OTHER than reacting to what the suspension on the OTHER side of the car is doing... It used to be called an ' anti roll bar '...
But it does have the 2nd function of locating the top of the spindle axially, i.e. preventing its motion forward and aft. So it serves as both an "anti-sway bar" and an "upper guide rod".

Pulling physics/engineering theory in, to forcefully locate the spindle in 3-D space, at least 6 forces must act on it. That is to counter 3 components of force and 3 components of rotation. The later 3 "moments" are termed "pitch", "yaw", and "roll" in aircraft. See if you can identify all such forces. Hint, the coil spring provides 1 force. If 7+ forces, it would be "over-constrained" and the reaction forces would fight among themselves (ex. push & pull in same direction).

Re other cars, Chrysler RWD cars had torsion bar springs from 1950's thru 1980's. In Aspen/Volare cars, it was L shaped. Porsche long used T-bars, as do some current pickup trucks. Re repair, they are easy to unload safely, and to adjust ride height (compensate for sagged springs). Most U.S. cars had wish-bone control arms. My old Chryslers have wish-bone uppers, but the lower has 1 pivot (like my M-B), with a guide rod going forward, term "strut rod" or "drag strut" (probably because it sees tension). I think most Chevy & Ford had similar LCA setups. FWD cars w/ struts & springs, usually have a wish-bone LCA. It seems sporty cars today have one for both upper and lower, i.e. "double wish-bone suspension" ads.
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  #25  
Old 04-20-2018, 04:29 AM
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Originally Posted by BillGrissom View Post
..... does have the 2nd function of locating the top of the spindle axially, i.e. preventing its motion forward and aft. So it serves as both an "anti-sway bar" and an "upper guide rod".

Pulling physics/engineering theory in, to forcefully locate the spindle in 3-D space, at least 6 forces must act on it. That is to counter 3 components of force and 3 components of rotation. The later 3 "moments" are termed "pitch", "yaw", and "roll" in aircraft. See if you can identify all such forces. Hint, the coil spring provides 1 force. If 7+ forces, it would be "over-constrained" and the reaction forces would fight among themselves (ex. push & pull in same direction)......
IF you are able to plot all the pivots provided by the upper and lower bushings acting on the spindle...and the coil springs... and the LOWER control ROD..
You should recognize some of those pivots as also being Fulcrums...when visualizing where the top of the spindle is allowed to move.. given the Lower Control Rod location.

you will see that all those are controlled and allow for the movements needed in the suspension..

ALL that is missing is the relative reaction left to right in a turn...... and that is what the Anti Sway Bar provides...

To attribute for-aft control.... which is considerable and needed due to brake reaction... to such PUNY rubber grommets on the firewall.... which allow only rotational movement up and down at 90 degrees to the longitudinal access of the car...
When the substantial bearings of the Lower control rod are determining the position of the upper part of the spindle via the multiple fulcrums/pivots involved is ignoring the obvious built in strengths of the components MB used for the system for a visual assumption of placement of attach point of the Anti Sway bar taking on a function it is not sufficiently built for or needed.
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  #26  
Old 04-20-2018, 11:09 AM
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Quote:
Originally Posted by Fulcrum525 View Post
I've had a front end wobble for some months now and have been waiting for spring weather to do a full front end rebuild. Today on the way home however I finally heard a "thunk" from the front and and instantly noticed I pull to the right under braking. I knew instantly that something broke. Thankfully it was close to home so I took it slow. Looks like the end of the torsion bar that connections to the upper control arm. I don't know what the end looks like normally to know if it still usable when I do the rebuild or if I'll have to use this saver. Mercedes Special Tools

https://imgur.com/a/2CBtF
To the OP, Fulcrum525:

1) You have not posted since your original post; that's good.
2) The advice in posts #2-#4 is the appropriate advice; the repair kits work well.


Last edited by vstech; 04-24-2018 at 09:00 PM. Reason: Removed insulting information.
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