Mystery Suspension Bar

[ejsharp]

While changing my rear brake pads I noticed that there is a bar that angles toward the front of the car from the rear wheels that has rubber grommets at each end. One end has severly worn grommets.. totaled actually.

Can these rubber grommets be replaced and what is the bar's function? Must the whole bar be replaced?

Smiles.

[JCE]

Hi:
It is a very important part in the handling of the car, and is a pretty inexpensive part to replace. Do a search under "Thrust Arm" "Control Arm" "Floating 300E" etc. Lots of descriptions of symptoms, part #s, prices (about $35 each), etc. Most 300Es seem to need them before 100,000 miles. I just did mine at 77k miles. The tech said they were worn, but still within limits for most drivers, and were good for another 20-30 k miles. I had him do them anyway, and I could feel the difference (Almost all of my suspension is new, and I could still feel a difference from just these arms!).

[yal]

Also to reiterate what JCE says the new bars apparently have been updated and are stronger.

[ejsharp]

Thanks fellas... that explains why the car does not handle well.

I'll check out parts shop to see how much they want for a pair.

Smiles.

[McLoffs]

Any idea how difficult it is to replace thrust arms? It seems that my car could use it. I like to work on the car myself but would certainly let my mechanic do it if I'm getting in over my head.

[Crowe]

I also just completed a brake job on my car and found the same situation with one of the rods in the rear suspension. The bushing on the "push rod" (third rod from the bottom front of the rear wheel) is all but gone at the end away from the wheel. It looks like it might be a simple process to replace. Can someone confirm that this is a DIY project. Each end of the rod has a bolt holding it in place. It looks like you could remove the old part and replace with a new one. Could this part be responsible for the loose feeling in the rear end?

[yal]

thrust arms???

124 Thrust Arm Confusion

Try these threads. There is a link by Arthur in the first one that has a picture of the thrust link. And try emailing evan for info on how he replaced his. Hope this helps.

[ejsharp]

I've recently completed replacing the right and left thrust arms on my car.... so I'm kind of an unofficial expert on the subject.

The job can be done with a minimal amount of patience, observation and common sense. Under normal circumstances the job would be straight forward... take the old one out and replace it with the new one... but in this case MB has redesigned the bar to make it more heavy duty. Essentially they have decreased the diameter of the bolts while increasing the diameter of the rubber grommet. It is the grommet that has been wearing out.

The old(original) nuts and bolts at both ends of the rod are 19mm and the new nuts for the bolts are 18mm. The heads of the new bolts are also redesigned so that you can not screw-up and put the bolts on the wrong way... they accomplish this by forcing you to put your wrench into the end of the new bolts (a star socket) rather than let you slip the wrench on the head from the side of the bolts. There is insufficient working room at one end of the bolts to slip a wrench in from the end... so there is only one way to insert the bolt and tighten a nut onto it.

Because the bolt hole at the wheel end is designed to have an 19mm bolt fit snugly into it.... and because the replacement bolt is a narrower 18mm bolt... the new bar comes with a kit that includes a metal sleeve that fits into the old bolt hole(wheel end of bar only). Once the sleeve is slid into the bolt hole; the new bar, bolt and nut can be attached. It is essential that this sleeve be used otherwise the car will not be aligned and there will be play in the suspension.

Tools need are 18mm, 19mm open end/box wrenches and a 3/8 drive star-socket and rachet and a standard 18 and 19mm 3/8 drive sockets. I think the star-socket is about 10mm. To make sure... buy the bar and kit and then take a bolt to Sears and get a Craftsman socket to fit the bolt or to another quality tool store or auto parts shop.

When replacing the bar connect the body end first and then the wheel end. You will need a helper to hold some tension on the wheel while the bolt is slipped into place at the wheel end of the bar.

Hope this helps.

Smiles.




[Edited by ejsharp on 04-23-2001 at 10:49 PM]

[Arthur Dalton]

*Note

Do not tighten bolts until you raise the axle to level.
[floor jack under wheel carrier]
If you tighten without doing this, the rubber get twisted in the strut and they will be in the strained position
when car is level. No good.

[ejsharp]

Arthur,

I do not understand what you mean. There is no strut on the rear wheels of a 300E. Do you mean the shock absorber? Or do you mean the stress on the rubber bushing that are in the rod being replaced?

If you are familiar with this procedure I have a question for you... maybe I figured the correct answer out when I installed the rods but I'm not sure... I simply don't remember.

The question is: What end of the new rod attaches to the wheel? The larger or the smaller end of the rod? The new rods are larger at one end than the old rods. The old rods are equal at both ends.

Thanks.

[Arthur Dalton]

Earl.
I am not sure we are talking of the same strut/arm, but any of them require leveling the axle before tightening so the bubber bushing/insert you mention on each end is not under a twist load when the car is sitting normal. So leveling the axle before tighten assures this.[ the bushing does not float on the retaining bolts and is sandwiched, so if the axle is hanging off-level, the rubbers will be twisted when car is let back on ground.
I just did torsion arms on an E320 with the new part from
Parts Shop and did not notice a larger end. I am wondering if you have changed the Torque strut vs Torsion.
Here is the job from the cd.
Would this be the same arm/strut?
Arthur
http://members.aol.com/ajdalton7/job113.jpg

[ejsharp]

You are right Arthur... we are talking two different arms. The ones I replaced are the upper arms (one on each side of car). They run from the top of the wheel on an angle toward the front of the car and then attach to the frame.

If you could look them up and check out the fat end I would appreciate it. I have a clink under the rear and I want to make sure I did not put them on backwards.

I suspect the clink is coming from the mounts of the center pot (rear gear box). The grommets are worn out on them too. Am waiting for parts from the parts shop.

[Arthur Dalton]

Originally posted by ejsharp
You are right Arthur... we are talking two different arms. The ones I replaced are the upper arms (one on each side of car). They run from the top of the wheel on an angle toward the front of the car and then attach to the frame.

OK. These are the Torque struts. Most parts houses refer to them as "Control arm struts"
Go to :
http://members.aol.com/ajdalton7/arms124.jpg

If you could look them up and check out the fat end I would appreciate it. I have a clink under the rear and I want to make sure I did not put them on backwards.

I have not seen the new version, but I think the larger end would go at the wheel carrier. Might want to ask the
tech's here that are familiar with the new design.

I suspect the clink is coming from the mounts of the center pot (rear gear box). The grommets are worn out on them too. Am waiting for parts from the parts shop.

More than likely. They are a common wear bushing.
Lastly, and I mention this 'cause I have not seen it adressed in these post on rear suspension, - the outer control arm bushings wear. This is a wheel carrier bushing
located at the connecting point of the control arm and carrier. [ kinda like where a ball joint would be on the front end.] Seems that the Curb side wears faster than the
other. A friend with a Benz Shop tipped me off on this one, and on mine, it caused a wobble like a bad tire belt.
Took some time in finding,but that seemed to do the trick.

Arthur