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Adjustable Trailing Arm Bushings
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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 to work.


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.


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