Rear Pitman arms bushings sudden failure?

vt · Post by vt » May 20, 2009 2:24 AM

Been flushing the brakes today, and suddenly noticed that all four bushings on rear Pitman arms are squished mercilessly out of the socket and obviously need urgent replacement. I can swear they were just fine less than a month ago when drive axles were being replaced, and the car made less than 700 miles or so since - I would've noticed. Or am I hallucinating?

The only thing worth mentioning in between was new tires installed and "alignment" done (with somewhat hilarious results, but that's another story for another day). Wonder if those specialists could've tried to do something to the suspension while trying to "align" it that could result in busted bushings. I don't think I'll go there again no matter what else I find, so the question is purely academical.

Now, do I understand correctly that the replacement is pretty straightforward? As in, http://www.bimmerboard.com/forums/posts/51281 plus corrections from http://www.mye28.com/viewtopic.php?t=33 ... pitman+arm plus some common sense adjustments (the car is somewhat lowered, don't know how much, so some lining up will be required).

Will Lemfoerder replacement kit http://www.rmeuropean.com/search.aspx?k ... 3321126476 do, or I'd want to go somewhere more exotic and buy the Pitman arms separately, and bolts, washers and locking nut piecemeal? Ultimately, the goal is a stable car, not cheapest replacement.

Post by **Shawn D.** » May 20, 2009 8:14 AM

The "dog bones" do not have bushings in them -- they're bearings. What you're seeing is probably torn boots (not good either), which doesn't mean the bearing is necessarily bad (yet). You don't need to replace the fasteners when you do these.

vt · Post by vt » May 20, 2009 11:23 AM

Shawn: I thought self-locking nuts (part 15 at http://www.realoem.com/bmw/showparts.do ... g=33&fg=30) are disposable?

bmws forever · Post by **bmws forever** » May 20, 2009 12:03 PM

Those are large bolts. I've reused successfully, but, do torque them down. I recall these being deformed nuts, not nyloc.

vt · Post by vt » May 20, 2009 12:10 PM

Sir, 127 Nm, Sir!

(rant) Just replaced the tires, decided to torque the wheels out of being paranoid - guess what, if you're not paranoid it doesn't mean they're not out there to get ya. The lug bolts torque was ranging from almost finger effort to all my weight on a long wrench necessary to release it.

Post by **Shawn D.** » May 20, 2009 12:24 PM

vt wrote:Shawn: I thought self-locking nuts (part 15 at http://www.realoem.com/bmw/showparts.do ... g=33&fg=30) are disposable?

I've reused self-locking nuts multiple times and have never had to replace one, nor have I had a re-used one come loose. It's pretty easy to tell that they still have squeeze when you reassemble.

Blue Shadow · Post by **Blue Shadow** » May 20, 2009 12:45 PM

Shawn D. wrote:I've reused self-locking nuts multiple times and have never had to replace one, nor have I had a re-used one come loose. It's pretty easy to tell that they still have squeeze when you reassemble.

Whereas Rod replaces the hardware as specified in the manual. His car shows it. Ours do not. I always wondered why these parts were specified for replacement other than increased repair costs, safety from our litigious society or TÜV requirements.

Rob_K · Post by **Rob_K** » May 20, 2009 10:48 PM

Meh, I always use the Lemforder and use their new hardware. It's just prettier.

vt · Post by vt » May 21, 2009 1:57 AM

Rob_K: too late

Karlyn set is on the way, let's see how shiny it is. Got a bigger problem now, though - just found that the clutch is dead... but that's a completely different story.

euro635gas · Post by **euro635gas** » May 21, 2009 12:47 PM

I tossed mine and never looked back. But I'm running Kmac adjusters.

vt · Post by vt » Jun 20, 2009 8:18 PM

I guess I should always be planning for the worst case on any car that I haven't owned from day one. Had I decided to go the expensive way and bought the Lemfoerder kit with fasteners included, I would've saved time and aggravation well worth the extra price.

Turned out, two washers were missing, and one bolt half-destroyed, with barely enough thread to put the nut back. Will have to replace it anyway, but well, it's Saturday and of course it is a special order item.

(big picture: http://tinyurl.com/kwqdr4)

I had to buy washers at Lowes, ended up with ones 2.1mm thick instead of 2.5, grade 8 hardened steel, yellow coated - do I have to bother ordering original BMW washers or the hell with it?

For what it's worth, dogbones that I took off the car look identical to the ones I put back on (Karlyn), and they don't look like they've been there for a long time - the metal is still clean and shiny, wonder how long to they live in extreme hot climates to begin with?

(big picture: http://tinyurl.com/mmhzbx)

Kyle in NO · Post by **Kyle in NO** » Jun 21, 2009 12:05 AM

They must have been installed incorrectly.

wkohler · Post by **wkohler** » Jun 21, 2009 12:08 AM

Kyle in NO wrote:They must have been installed incorrectly.

times two

mercury26 · Post by **mercury26** » Jun 21, 2009 12:32 AM

The PO of my car installed one upside down and it was pretty torn up. I think people install them without realizing their is a top and bottom to them.

Cheers,

Chuck

vt · Post by vt » Jun 21, 2009 12:46 AM

Interesting... I didn't realize there's a top and bottom to them, either. Looking again at the parts I took off, still don't see the difference - other than technological leftovers from casting, that is. I'll rip them open and see if there's any - will have time to do that in about an hour.

Meanwhile, can you tell me, please, how do I distinguish top and bottom? Is 30 miles trip going to destroy them if they're installed incorrectly?

The boots are not only torn, but cracked as well, looks like normal wear for this climate. But then again, what do I know...

mercury26 · Post by **mercury26** » Jun 21, 2009 1:03 AM

If you look at the center casting, the part that links the two bolt hole sections. One side is more rounded than the other, so one side is flat and one is rounded. I agree hard to see on the Karlyn-STI part, but their is a difference.

I believe the rounded part is facing down towards the ground. I used the following link as a guide for installation.

http://www.bimmerboard.com/forums/posts/51281

Cheers,

Chuck

vt · Post by vt » Jun 21, 2009 2:43 AM

Damn! I see it now.

Funny thing is, I was looking at this exact article when I was replacing arms, but couldn't see the difference (even when the parts came) and decided that it must be because the seven uses different parts. That's what you get for being blind.

Strike me the lightning, though, if I can make out which side up are they installed

I'll get to the car in the morning, meanwhile, I'll rip open the old part and see what exactly causes incorrectly installed part to go bad.

Meanwhile, for those poor sods that are following the same footsteps, here's the picture that points out the differences (read the notes): http://tinyurl.com/nqvtgt

vt · Post by vt » Jun 21, 2009 4:33 AM

All right, here:

(big picture: http://tinyurl.com/l2262p)

Whereas I do see how the part is anisotropic, I still don't see why the change of orientation will make it fail. If I understand the physics correctly, the load is applied mostly from bolt to bolt under car's lateral acceleration, plus some torsion when the trailing arm is going up and down. Doesn't make sense. Even the fact that the whole part is asymmetrical is irrelevant - you can't see it from the picture above, but the plastic insert is lined up right across the middle of the bridge, and one side is higher is just because the machined steel insert needs something to cling to.

I'm very skeptical now. I'd rather blame manufacturing quality than installation orientation - unless I'm missing something obvious. What am I missing?

Update: Ah, what the hell - here's one more picture. See how the insert is lined up with the bridge:

(big picture: http://tinyurl.com/n89hkd)

m535is · Post by **m535is** » Jun 21, 2009 9:18 AM

I am in agreement with VT. The only reason there is a difference in the casting is to be able to assemble the part. The part is universal. I have installed them in all different orientation and they all last about the same time. The key is making sure the washers are in the correct orientation.

Hope this helps,

vt · Post by vt » Jun 21, 2009 1:32 PM

m535is: did you install star washers? The only washers that were here (and it seems from RealOEM diagram that those are the right washers) are the flat ones, I don't see how orientation would matter.

I'm a bit concerned that I had to install washers from Lowes, not BMW ones (see above, but not that much - I'll be keeping a close eye on it.

m535is · Post by **m535is** » Jun 21, 2009 10:12 PM

The only washers I used were the ones that came with the Lemforder parts. I don't think the thickness of the washers will matter as they are not used as spacers, but for some reason the washers in my rear suspension were in between the pitman arm and subframe. I think that caused them to fail faster than the should have.

Hope this helps,

vt · Post by vt » Jun 23, 2009 4:10 PM

I wonder if all dogbones are created equal. Looking at this specific item (most likely Karlyn) and seeing a plastic insert, I don't feel much confidence - wonder if other manufacturers also use plastic, or something more durable?

wkohler · Post by **wkohler** » Jun 23, 2009 4:15 PM

I used Meyle last time I did dogbones (old 533). I didn't drive the car more than 1600 miles after that, so I couldn't say one way or the other about quality.

vt · Post by vt » Jun 23, 2009 4:16 PM

This one is a daily driver with about 1000 miles a month, I guess we'll see soon enough.

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Rear Pitman arms bushings sudden failure?

Rear Pitman arms bushings sudden failure?

Autopsy

Afterthought