Rear trailing arm bushings and pitman arms.

E28 technical advice asked and given! Troubleshooting, modifications and more.
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Klimpaloon
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Joined: Apr 26, 2022 10:43 AM
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Rear trailing arm bushings and pitman arms.

Post by Klimpaloon »

My trailing arm bushings need to be replaced. I was looking at the powerflex poly bushings but heard I need to remove the pitman arms. Is this safe or should I go with the e34 m5 bushings?
Shawn D.
Beamter
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Re: Rear trailing arm bushings and pitman arms.

Post by Shawn D. »

First off, welcome to the site -- please read & heed the Tech and Forum FAQ sections.

Did you bother to do any searches before asking? If so, what did you find?

What do you mean by "remove"? What are the instructions, specifically? Not what you "heard."

Here's just one thread on these, and the member didn't delete the pitman arms: viewtopic.php?t=149025
Klimpaloon
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Re: Rear trailing arm bushings and pitman arms.

Post by Klimpaloon »

Garagistic says to remove the pitman arms in their instructions or the polyurethane will bind. https://www.garagistic.com/collections/ ... m-bushings

In this video they need to move side to side with the pitman arm attached but the polyurethane doesn't allow that movement. https://www.youtube.com/watch?v=dWwAHqHFX5I

In the thread you linked bafbaf said he wouldn't trust the bushing mounts to support the cornering load. I wanted to know if going with polyurethane was a good idea or not, and others opinions on if the bushing mounts could support the stress without the pitman arms installed.
jc72
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Re: Rear trailing arm bushings and pitman arms.

Post by jc72 »

I don’t know if you need to remove them but you can safely, very early production e28s and low power euro models (518i/520i) didn’t come with them at all.
Shawn D.
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Re: Rear trailing arm bushings and pitman arms.

Post by Shawn D. »

Your initial post said Powerflex, but you are referencing Garagistic instructions. They're different products. The link I provided was about Powerflex bushings.

I would not remove the Pitman arms. I'd go with the E34 M5 bushings.
athayer187
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Re: Rear trailing arm bushings and pitman arms.

Post by athayer187 »

IMHO - this is an application where urethane is not an appropriate alternative. These bushings need to rotate and translate (slide sideways). The M5 bearing solution is more work, but worth it.
adam_poll
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Re: Rear trailing arm bushings and pitman arms.

Post by adam_poll »

I don’t know if you need to remove them but you can safely, very early production e28s and low power euro models (518i/520i) didn’t come with them at all.
Car's that came without the pitman arms (my 1984 525i included) have completely different rear subframes and trailing arms to a car that has them, the angle that the suspension pivots on is actually different (more, not a good thing!) so I would not take that as proof you do not need them. My car has since had the standard rear end retrofitted to it and I run the pitman arms with new, stock bushings.

Like others have said there are better options (including new stock in my opinion and my car is regularly pushed to the limit on track with them) then poly for this location. Poly works great for the subframe mounts though and likely makes a bigger difference there to the rigidity of the rear end.
jc72
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Re: Rear trailing arm bushings and pitman arms.

Post by jc72 »

adam_poll wrote: Apr 29, 2022 11:24 AM
I don’t know if you need to remove them but you can safely, very early production e28s and low power euro models (518i/520i) didn’t come with them at all.
Car's that came without the pitman arms (my 1984 525i included) have completely different rear subframes and trailing arms to a car that has them, the angle that the suspension pivots on is actually different (more, not a good thing!) so I would not take that as proof you do not need them. My car has since had the standard rear end retrofitted to it and I run the pitman arms with new, stock bushings.

Like others have said there are better options (including new stock in my opinion and my car is regularly pushed to the limit on track with them) then poly for this location. Poly works great for the subframe mounts though and likely makes a bigger difference there to the rigidity of the rear end.
Interesting. I made my post based on what I’ve heard but have never actually seen the stock setup without pitman arms. If you or anyone has pics id be curious to see how it differs.
adam_poll
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Re: Rear trailing arm bushings and pitman arms.

Post by adam_poll »

I went digging on Realoem and it actually shows my car had pitman arms but my memory says different, those pieces were long ago scrapped though. The other difference with this setup is the trailing arm bushings, they used the same 30 mm bushings that were used on the E30 and a bunch of other cars rather than the 44 mm bushings the majority of North American E28's got.

To the original question, the pitman arms serve a purpose trying to keep toe in check so using a poly bushing that prevents that from happening sounds like a downgrade to me.
LeiseyJr
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Re: Rear trailing arm bushings and pitman arms.

Post by LeiseyJr »

https://youtu.be/dWwAHqHFX5I

With e34 m5 trailing arm bushings, the pitman arm is what controls the arm through its travel.
4x4_e30
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Re: Rear trailing arm bushings and pitman arms.

Post by 4x4_e30 »

I just dropped my subframe to install eccentrics after having the Garagistic poly bushings in for the last 10k miles. I greased them sufficiently, but failed to read the warning about needing to remove the pitman arms. Long story short, I've been having weird toe issues in the rear right lately, and a ominous popping sound coming from the back when pulling out of driveways in the last thousand or so miles. The inside of the bushing wore out between the spacer and the poly. Had about 3/16" of vertical slop with a prybar.

So if you're going to install poly bushings, take the pitman arms off. Poly bushings will not deflect enough for the pitman arms to do anything other than bind everything up and accelerate wear.
szacsi72
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Re: Rear trailing arm bushings and pitman arms.

Post by szacsi72 »

Poly for the trailing arm sucks, period. Don't install them. If the M5 RTABs are steep, just get stock ones, even those will be better.
I don't recomment to remove the pitman arms - altough you could - , because these subframes and arms were designed in a way so that the pitman arms will carry most of the sideways load. Remove the pitmans arms and add the poly, you may actually get more complience from the system than stock rubber due to bushing overload.

I have polys in mine installed by the previous owener. They suck. I will remove them when I do my suspension overhaul.
LeiseyJr
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Re: Rear trailing arm bushings and pitman arms.

Post by LeiseyJr »

The M5 RTABs are very difficult to get right now. Quite annoying
szacsi72
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Re: Rear trailing arm bushings and pitman arms.

Post by szacsi72 »

LeiseyJr wrote: Mar 07, 2023 2:05 PM The M5 RTABs are very difficult to get right now. Quite annoying
If anybody happens to need some, I think I can hook you guys up. I have access to multiple parts stores that can order for me from the manufacturers directly trough my company. However, please note that I'm in europe, so if you are in the US, this won't be a good deal for you. I'm just letting you know in case you really can't find any.
4x4_e30
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Re: Rear trailing arm bushings and pitman arms.

Post by 4x4_e30 »

My new set of M5 bushings just showed up in the mail from ECS. They are Hamburg-Technic brand but seem to be well made and their other parts get good reviews. I guess only time will tell.
Blue Shadow
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Re: Rear trailing arm bushings and pitman arms.

Post by Blue Shadow »

4x4_e30 wrote: Mar 11, 2023 11:07 AM My new set of M5 bushings just showed up in the mail from ECS. They are Hamburg-Technic brand but seem to be well made and their other parts get good reviews. I guess only time will tell.
First time I have read that Hamburg-Technic parts get good reviews. I haven't hunted for reviews but back when Uro started and H-T was available there was talk of a number of brands of front end parts weren't very good.

Hopefully this is true and the bushing work well for you.
neilg
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Re: Rear trailing arm bushings and pitman arms.

Post by neilg »

4x4_e30 wrote: Mar 11, 2023 11:07 AM My new set of M5 bushings just showed up in the mail from ECS. They are Hamburg-Technic brand but seem to be well made and their other parts get good reviews. I guess only time will tell.
Did you fit the Hamburg technic bearings yet?
ElGuappo
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Re: Rear trailing arm bushings and pitman arms.

Post by ElGuappo »

Are the E32 740/750 trailing arm Bearings a different part number?
They work and fit perfectly, and might avoid the //M tax.
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