Re: [bmw] E28 control arm bushing

[mkohlbrenner@xxxxxxxxxxx]

"Watry, Andrew (LNG-SFR)" <Andrew.Watry@domain.elided> wrote:

> Is it the upper control arm (also called the "push strut"?) bushin
> that commonly wears out on E28s, not the lower control arm?

I forget which is upper or lower, but it is determined by the location
of the ball joint at the steering knuckle.  In any case, it is also
commonly called the "thrust arm".  It is the one that is at an angle
of approx. 45 degrees in and to the rear.  And yes, this is the one
that does cause the most notable symptoms when it wears -- shimmying
@ ~55 mph and/or while braking or simply some vagueness in the
steering.

> If so, a couple
> questions:
> * I've heard of a bushing upgrade; is it the 750 bushing?

Yes, the 7-series bushing will be somewhat firmer and will last
somewhat longer.  However, you do have to be careful on the E28
because the mount on the car is narrower than in the 7-series.
You have to ensure that whoever sells you the bushings has
properly modified them for the E28 by shaving down the outside
edges.  I don't know any more details than that, but anyone who
sells these things SHOULD know all about this.  If they don't,
politely hang up and try somewhere else.

> * If the bushing is worn out, is it common that the ball joint at
> the other end is worn too, and it makes sense to replace the whole
> arm rather than press in a new bushing?

It depends somewhat on your driving.  If you drive hard or have bad
roads that really work this bushing, they can last as little as
30K-50K miles.  Ball joints are probably good for 100K or better.

There are plenty of places that will sell you the arms complete
with 7-series bushings pressed in.  That saves you hassle in two
ways.  First, you don't have to hassle with popping the ball joint
without damage -- just have at it with a pickle fork if you want.
Second, you don't have to hassle with pressing the bushings out/in.

I don't know if they have the "narrowed" version bushings for the
E28, but bmaautoparts.com has E34 arms with 7-series bushings
pressed in for $160 a pair.  At that price, I plan to just do the
complete arms this next time around.  Other places sell just the
bushings for almost that much for the pair.

> * It looks like a possible home-repair job without having to
> remove/compress the strut.  True?

Yes.

One additional thing to note:  Do NOT tighten the bolt that goes
through the bushing until you have put the car back down on its
wheels and have put some dead weight in the front seats to
simulate humans.  If you do not do this, you can end up with a
shimmy and will definitely NOT get proper service life out of
the new bushings.

Regards,
Mike Kohlbrenner
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