Wobble Shimmy Vibration in front end - running out of ideas - PeachParts Mercedes-Benz Forum

rhodes2010 · #1 11-08-2012, 04:56 PM

I have searched through all the discussions on front end wobble vibration and shimmy and if the problems were resolved I never saw the solutions.

The 1983 300SD W126 has new balanced Pirelli P4 tires on all 4 wheels.

Car was aligned by a local shop that always tells me when a part is worn or
broken (and of course wants me to have them put it in).

I checked rotor run out in the front and only got .001 inch on the outside
surface. Checked close to hub and outer edge of rotor.

My brake pads are down to last few thousand miles and will get changed
soon. But brake pads are within service life/tolerance.

The vibrations started under braking and gentle braking keeps the vibration under control and not severe.
I am starting to feel the vibration over some rough surfaces.

My first thought was to raise front end and grab wheels and all parts
and look for loose, worn, anything that moved.

Control arm bushings check out and are there and not disintegrated.
Ball Joints not loose.
Tie rods ends not loose, boots in good shape (one tie rod is new).
Idler arm appears solid (alignment guys caught this on other car).
Wheel bearings appear to have no play.
Rotor runout is .001.

I can count on the alignment shop to recommend problems they see .
On this car , which they saw two weeks ago, they said nothing.

I found one thread, with one recommendation, that the steering dampener
can cause this kind of vibration under braking and over bumps.

My question to you all is:
if rotor runout and bearing are not the problem, if all other parts check out.
With new tires installed.

Got another place I can check ?
Can a dampener possibly solve this ?
Can shock absorbers cause this ? (shocks are Billsteins with 150,000 miles on them - 6 years old)

Dampeners are cheap enough, but I hate throwing parts at something
without being able to measure or test them.

Thank you for your help.

Dubyagee · #2 11-08-2012, 05:02 PM

Mine did the same until i got a road force balance on four new michelins. The place was called TreadQuarters and got them 100mph perfect.

iPhone 4

rhodes2010 · #3 08-13-2013, 12:28 PM

The ultimate answer seems to be, tighten the steering box.

After a few hundred miles the vibration during braking seems to be gone.

I did replace the idler arm bushing and the steering dampner.

I had never tightened up the steering box on this one.
Used a 19mm socket to crack the nut loose.
A 6mm allen wrench to screw the center outward while
rocking the steering coupler back and forth until I could see pitman arm
move in better relation to steering coupler.

Hold the nut with a 19mm wrench while turning the 6mm outward.
When finished, tighten the 19mm nut again.

Noticeable difference in the steering and vibration.