Swing arm bushing blowing out of side

[leonard]

Hello
I'm seeing a problem with my rear swing axle bushing. The inner bushing on the right control (thrust) arm is blowing out and over the cover plate. This is happening on both of my cars; w111 and w113. It is the same bushing on both cars. The w111 was rebuilt by me about 2012. The w113 was rebuilt by a local shop 2 years ago. 
Details:
W111: 1965 220SEb rear axle has never been rebuilt but swing arm has been rebuilt in 2010, the bushing was gradually  blowing out on top and was replaced again in 2012. Bushings came from AutoHauz AZ not sure if OEM
W113: 1967 250SL complete rear axle rebuild in 2019. I bought the car 2020 and rear axle was fine, not sure what bushings were used.
I haven't found this problem when I do a forum search of this site and MBCA site.

The cause is probably my driving/driving style, which is not going to change. But this may not be true

Questions are:
 Would switching to urethane bushing prevent this?  Has anyone else seen this problem and what fix did they do that worked?

I don't want to get into 'have you tried this or that' as this is a bit of major repair and I have set camber/castor on w111 to correct settings based on age and wear of the rear end, so taking this apart requires me to disassemble the shims that were used on this side
thanks Leonard

[ja17]

I have heard others complain of even new bushings from the dealer failing prematurely.

[wwheeler]

When I installed my rebuilt rear axle, I had similar issues on my W111. The rear arm bushings were installed by the rebuilder. When I finally bolted it up, the bushing looked so out of alignment to me that I ended up replacing those bushings. When I took the rubber bushings out, I noticed a lubricant on the outer coned surface of the bushing as well as the inner. The grease obviously allows the rubber to slip some on a metal surface making installation easier. But it also allowed the bushing to ooze out on one side like yours.

Bushings like these don’t move much and flex internally. They shouldn’t actually slip on the mounting surfaces when in operation. Therefore when I installed new rubber bushings back when, I did NOT use lubricant on the outer coned surface and just on the inner. That helped quite a bit although it is still not perfectly centered.

I think urethane would help and only because it will not flex as easily as the OEM rubber. When I redo mine again one day, I will use the urethane because of this issue. That being said, I do sell the urethane bushings for this application and this would appear as a self promotion. It really isn’t and I am very familiar with rubber and urethane and worked in that field for 35+ years. I had already decided a couple of years ago I would use urethane in this application.

[leonard]

Wallace
thank you, I believe I used liquid soap to help lubricate the bushing during assembly of OEM bushing. I was thinking urethane might be a solution, I'm using them on my front suspension, I'll have to order some.  I've done this job back in 1995 and don''t recall this problem occurring, but I was living in Central California that was mostly straight roads. Now I live along Pacific Coast Mountains and go out on club rides.   

Both cars suffer from the same problem with the same bushing. Instead of aligning both bushings equally, I may try to get the the problem-side bushing pressed further in and see if that fixes the problem. My suspicion is that this problem is due to cornering. Car has Michelin Pilot tires which allow me to corner better than w113 (although I do switch wheels sometimes)
thanks for technical input

[mnahon]

Reading this thread made me go have a look at my trailing arm bushings, which I replaced 7-8 years ago. Sure enough, same problem. They're blowing out toward the inside, on both sides of the car. I'm pretty sure I used liquid soap as lubricant when installing; and I bought the bushings from SLS, i.e., they're repros.

Looks like I'll be adding one more job to this winter's list. Any suggestions for how to do a better job are welcome.

[leonard]

Meyer
Mine are OEM, I suspect this occurs because of how we drive them; I'm not easy on mine, I do drive them hard. Urethane bushings might be an improvement and not using soap may help. but assembling without some lubricate makes this hard.

One thought I have was to create a 'U" bracket that is threaded on both ends, then place over the bushing housing and tighten both ends, holding the washers captive and preventing the bushing from blowing out the side. 

[mnahon]

In the 7-8 years since I've replaced mine, I've done about 20,000 km. Of that, probably 80% was on highway (i.e. straight roads). So even if I've done some spirited driving, it's not much in an absolute sense, and I find it hard to believe that my driving style did this in such a short time.

This U-bracket you're suggesting, is it just during installation, or something that would stay on the car permanently?

[leonard]

I was thinking of it as a adjustable 'U' clamp that would have two fasteners on each end. You would tighten one end as the washer pushed out.  For now I' going to replace that one side. I've got a few OEM bushings laying round the garage

[Benz Dr.]

Make sure you have your trailing arms on correctly. They are sided LT&RT and can be installed backwards.

[JohnnyC]

Thank you Benz Dr.  How do we tell them apart, they look the same to me?  Are all of the model year W113s the same trailing arms?

Cheers,
JohnnyC

[Benz Dr.]

They all use the same trailing arms. If you look at the area that holds the bushing that goes around the stud mount, you will see that a partial plate is welded to the bottom edge of the cup on the trailing arm.  That partial plate or flange should point inwards towards the driveshaft on both trailing arms. I think most arms also have L or R stamped into them. It's possible to put them on wrong but I can't say what the results would be. They would never leave the factory that way so if they're wrong, someone put them on that way.

[mnahon]

Hi Dan,

This issue of left/right trailing arm just consumed a couple of hours of my morning. It was discussed in this thread, where there's a picture of what (I think) you're explaining.
https://www.sl113.org/forums/index.php?topic=21553.msg153408#msg153408

I went to check my car and I think it conforms to what you're saying. First picture below is of my left trailing arm.

For confirmation, I took a look at a car presently posted on BaT (blue one) and it also conforms to this. See second picture below.

I then looked at a bunch of other cars sold on BaT and in most cases where there's a picture where this feature is visible, they also conform to this same layout.

Here's one exception where the arms seem to have been reversed (see left arm which is on right side of pic 298).
https://bringatrailer.com/listing/1968-mercedes-benz-280sl-22/

Finally, I wanted to point out that in the thread I pointed to above, the labeling that Naj had put on the arms (green L and R) appear to be incorrect. When I orient that picture the same as the other pictures I have above (see third picture below), I would get the opposite labeling. If others agree, I can try to post a note on that thread warning that the labels are incorrect.

Thanks,

Meyer

[Benz Dr.]

I figured that someone would have already posted about this.