Got a slight shimmy a few mph on each side of 55 mph. Above and below 55 everything is pretty good. The shimmy isn't horrible, but it's definitely noticeable. Where do I start looking for the cause?

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Len
'59 220S Cabriolet-SOLD and living happily in Malta
'83 240D 351,500 miles original owner-SOLD
'88 560SL 41,000 miles - totaled and parted out
https://sites.google.com/site/mercedesstuff/home
'99 E300 turbo 227,500 miles
'03 SLK320 40,000 miles - gave to my daughter
'14 Smart electric coupe 28,500 miles
'14 Smart electric cabriolet 28,500 miles
'15 Smart electric coupe 28,000 miles

Wheel balance.

Nah... Diesel purge and Italian tuneup, or Windex.

I’d start by balancing and or rotating tires. Does the steering wheel move during this?

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Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (113k)
1991 350SD (206k)
1991 300D (228k)
1993 300SD (291k)
1993 300D 2.5T (338k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (265k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)

Check Tire inflation. How about the Wheel bearing end play?

Inspect the Tie Rods for play and so on with the other steering parts.

Look at the Rubber Donuts at the end of the Torsion/Sway Bar where the Sway Bar goes through the upper control arm.

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84 300D, 82 Volvo 244Gl Diesel

Check wheel balance first, vibration there can introduce a harmonic in the steering and/or suspension (particularly if there's play in some of the joints) at a particular frequency. Once the tires are balanced the 55mph shimmy will probably disappear, at least until the ongoing wear in the suspension components reaches a point where something else triggers a new harmonic. Wheel bearing play and alignment could also be a factor, all those tiny amounts of backlash in the assembly add up.

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Started with the easy stuff - got the wheels balanced and rotated and the shimmy has just about disappeared. I might be imagining that there is still a little shimmy because I'm looking for it. But I don't think the average driver would notice anything. The car really is back to riding on rails again. Feels nice.

__________________
Len
'59 220S Cabriolet-SOLD and living happily in Malta
'83 240D 351,500 miles original owner-SOLD
'88 560SL 41,000 miles - totaled and parted out
https://sites.google.com/site/mercedesstuff/home
'99 E300 turbo 227,500 miles
'03 SLK320 40,000 miles - gave to my daughter
'14 Smart electric coupe 28,500 miles
'14 Smart electric cabriolet 28,500 miles
'15 Smart electric coupe 28,000 miles

Worn shock absorbers can cause this, as well. When they are worn out, they won't dampen the vibrations in the road and this translates into side-to-side play in the steering if there is looseness in it. My roommate's W126 would shimmy harshly above 70 MPH even though the wheels were balanced. After replacing the front shock absorbers, the shimmy went away.

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DON'T MESS WITH MY MERCEDES!


1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Highly Optioned, 350,000+ Miles