Adjustable Trailing Arm
Installation of adjustable
trailing arm bushings - submitted by Michael Hunt, January, 2010
Many Z-3 owners have mentioned their concern
relative to the fact that these vehicles tend to wear the inner side
of the tires more quickly than the center or outer side of the tire.
This is especially true of vehicles that have been lowered via the
installation of non-OEM springs. This uneven wear is caused by BMW's
quest to deliver a vehicle with world class handling traits. The
vehicle is designed with a negative camber at the wheels. What this
means is that the tops of the wheels are canted in toward the center
of the vehicle. This is great for handling, but can cause havoc to
your tire mileage.
I recently installed a set of the above mentioned bushings in my 1998
M-roadster. Thought I would pass along some of the lessons learned
that are not pointed out in the directions. I used the kit from
Bavarian Motors because they provide a little tool with the kit, which
allows you to remove the stock bushings without totally removing the
trailing arm from the vehicle. You don't have to have the bushings
pressed out with a …..press. This means you don't have to disconnect
the brake lines.
The first lesson learned was to disconnect the axles from the
differential. You can still leave the emergency brake cables and brake
fluid lines connected. But by disconnecting the axles, you can get the
trailing arms far enough away from the cross-member to give you room
The second lesson learned was that if your current bushings are in
pretty good shape, that tool won't quite get the bushing all the way
out of the arm. The simple expedient of adding a couple of washers
between the drive nut and the bushing will allow it to push the
bushing all the way out. This will make more sense when you are
actually looking at the instructions (available on their website) or
holding the pieces in your hands.
The most important lesson learned relates to the way they make the new
bushings adjustable. The inner core of the bushing has a D shaped
hole, off-center, through it. The bolt that goes through this hole is
also D shaped. It would seem a simple matter to align these flat spots
when you are installing the bolt. But when the bushing is installed
and wedged up between the mounting ears, it is not that easy to see.
And the exact orientation of the flat spot on the bolt is not that
easy to see either. The bolt is soft enough to allow you to get it
partly installed even though the flat spots are not properly aligned.
Ask me how know. Then you have a bolt half way in that does not want
to move in or out for love nor money. Don't ask me how I know. Anyway,
the solution is pretty simple. Mark the head of the bolt and the inner
side of the bushing with the locations of the corresponding flat
spots! Then when you install the bolt, you have clear references to
the proper orientation. I went ahead and cut a small line in the bolt
head so that I will have a clear reference in the future when
readjusting the bushing. Since the beauty of this setup is that you
can minimize the camber for normal driving. But if you are heading to
the track, in about thirty minutes, you can maximize the camber.