Vibration at Speed

[poland1 <polands@xxxxxxxxxxxx>]

Sean,

I would agree that the first thing to look at with a 55mph harmonic
vibration is wheel balance.   Could also be sometning like a blistered
tire tread, but I would think that would be pretty obvious to someone
doing a wheel balance.

However having gone through a growing problem like yours during my
ownership (75,000miles - 160,000 miles) of a e28 535is, I eventually
recognized that my front suspension components were all in need of new
"wear and tear parts", ie ball joints and bushings.  Basically it got so
loose that while it may have been aligned when static in the shop, there
was no way it was staying in any particular alignment while on the road,
going through various acceleration, breaking, cornering, pavement ruts
and bumps each completely change all the alignment attributes.  After
thoroughly renewing these front suspension pieces, the car has become
totally civilized, no vibrations, no tramlining, no odd tire wear.

Have a trusted shop take a look at front suspension.

Steve Poland
'88 535is
Portland, OR