Strong steering vibration after hitting imperfections on the road

[dragon850]

This is for my friends car, I can't figure this out. Driving on the freeway after hitting a pothole or some bigger imperfection he gets a death rattle in the front suspension.
When you let off the gas bring the car below 50 mph ride smooths out again and he can speed up smooth till he hits another imperfection.
Both upper and lower control arms changed, sway bar links changed, tires are new, balanced, alignment done, upper mounts new.
Car has bilstein shocks, one of them I can compress with my hands but not easy.... the other I cannot. Is it safe to assume shocks are bad??

[mandd]

Front Shocks.

Mark.

[SanDiego850]

I've had the death shimmy for years. New tires help for a bit.
All new steering components changed, and shocks, still there. I have 18 inch wheels but I think the only thing that might help is 17's with more rubber.

[Chamberlin]

Stuck caliper... Is it an 840ci with Brembos?

[CD05001CIA]

Knock a wheel weight loose or off. I see them all over the place.

[dragon850]

I've had the death shimmy for years. New tires help for a bit.
All new steering components changed, and shocks, still there. I have 18 inch wheels but I think the only thing that might help is 17's with more rubber.

Tires are new, it's weird it's smooth till you hit a pothole. 18" M pars.

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Stuck caliper... Is it an 840ci with Brembos?

It's an 850 with big brakes, but shimmy only happens after hitting a pothole, otherwise smooth.

- - - Updated - - -

Knock a wheel weight loose or off. I see them all over the place.

Tires re balanced, did not help.

- - - Updated - - -

Front Shocks.

Mark.

That's what I am thinking...

[Chamberlin]

Oh I interpreted the original message incorrectly ... I thought it was a continuous problem at certain speeds ever since hitting that one pothole... But you're saying that it just takes any pothole or road imperfection to get it oscillating (if you're at a particular speed range when it hits). That is most likely a combination of worn parts, and yes a failed strut not being able to dampen out the system's resonant oscillations. Happened all the time on my lifted jeep, related to big tires and a steering geometry problem. In this case, it seems to be a vertical suspension motion oscillation.

[Stantz]

How long does it vibrate after hitting a pothole? A few seconds?

[dragon850]

How long does it vibrate after hitting a pothole? A few seconds?

Vibrates until the speed is reduced, then again no problem after speeding up.

[Dr. T]

Can also happen with loose steering components. Steering box, tie-rods or the infamous idler arm bushing....wears out like the upper control arm bushings....

[Stantz]

I’d agree with the shock absorbers being bad, or at least one of them is.
Especially if you can compress one of them, and you can’t compress the other one.

[shogun]

Had a similar problem with a friends E32 Alpina B12, that also started shaking like hell. We changed among others for testing + some were dead already: shocks, wheels, tires, center bearing of drive shaft, engine mounts, trans mounts, front brake discs, rear dog bones and beer cans etc pp., in the end it turned out if was the center steering tie rod, one of the 2 ball joints was totally damaged, http://www.bmwe34.net/E34main/Mainte...ering_link.htm

[jehu]

it turned out if was the center steering tie rod, one of the 2 ball joints was totally damaged, http://www.bmwe34.net/E34main/Mainte...ering_link.htm

Was this evident while the damaged part was still installed? Did it appear weak when manipulated with a pry bar?

I have some minor shaking during braking and some slight vibration in the steering yet have replaced; Upper control arms+750i bushings, lower thrust arms (aluminum), both complete steering tie rods, struts and strut mounts yet the center link appears solid when a pry bar is used to apply forces. I have the center drag link and a new idler arm bushing but was going to return the center link however I had to ask if perhaps despite appearing sound to any possible examination while installed it can yet still be damaged.

[shogun]

Not really evident when installed. After we disassembled it and compared the tightness of the ball joint, it became clear that this was the main problem.
Note that there are also differences in center tie rod/draglink LHD vs RHD. Important info for our members from RHD and LHD countries. Many members from RHD countries order parts in the U.S., but always carefully check if they really fit your RHD car.
I recently bought a new LHD Febi center tie rod for my 750 LHD and installed it and we discussed about the difference between RHD and LHD. My wrenching buddy said there is a difference, but we did not know the difference, and here I found it with pics
http://bigcoupe.com/phpBB2/viewtopic...ht=rhd+problem

This confirms the findings on my original BMW draglink for LHD. There are 2 connections/ball joints on a drag link, 1 is basically solid/fixed, the other one is much more flexible, the old one I took out and also the new one, so the RHD versions is just the opposite side. The shape of the metal at the bottom is different. I also check my old one, it looks the same, one ball joint is differently preloaded. So the shape of the drag link is the same LHD and RHD, it will fit, but the preload is on the opposite side.
And I checked a bit more pictures and much to my surprise some of the cheaper aftermarket draglinks show no difference in the shape of the bottom part of the draglink, so I wonder if they just make these to fit RHD and LHD without the small differences BMW and the better brand ones make in ball joint preload?

Edit: just have to add another 'funny' story where we searched a long time on an E32 750. The steering box was not tightened enough and under certain road hard conditions it slightly started moving, causing steering vibrations. #5,6,7 and 2,3,4 http://www.e32-schrauber.de/bmw/date...nkgetriebe.jpg