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Old 08-25-2013, 03:52 PM   #4
Dog Chauffeur
DRONE's Avatar
Joined: Oct 2007
Location: Tacoma, WA-ish
Oddometer: 4,089
The Wreck--Part One

Before I begin describing what happened, I want to state a few observations and opinions--
  1. My sidecar outfit tips the scales at over 1350 lbs when rider, dog, and camping gear are on board--well over the recommended 1100-lb max load rating of an 1150GS Adventure.
  2. I drive my sidecar hard (ask around).
  3. I use my sidecar extensively on rough, uneven surfaces.
  4. The BMW telelever front suspension is an innovative and utterly reliable suspension when used on an ordinary leaning motorcycle where, essentially, all it has to do is go up and down.
  5. On a sidecar rig, the front forks are subjected to powerful lateral forces that are absent on a leaning motorcycle.
  6. The telelever is connected to the lower fork bridge by the ball joint. ALL the lateral forces that are generated during a sidecar turn are transmitted from the forks to the frame through the ball joint.
  7. If the ball joint connection fails, the telelever suspension fails.
  8. The BMW/OEM lower fork bridge on my 1150 was replaced by the previous owner at 50,000 miles with an aftermarket lower fork bridge that reduces trail and results in easier steering. There is no way to determine if this part was installed correctly. The only way to know if it gets done correctly is to do it yourself, or observe and verify as somebody else does it.
  9. If the ball joint is under-torqued, or over-torqued, or installed without high strength threadlocker, there will be a tendency for the connection between the ball joint and the lower fork bridge to fail due to metal fatigue.
  10. The outfit was driven for 23,000 miles after the steering modification was installed with no sign of any problem.

Note that the threads of the steel ball joint are filled with aluminum alloy, and that there are no threads remaining in the ball joint fitting on the lower fork bridge. What happened, simply, is that the ball joint pulled the threads out of the bridge. Once that occurred, all that was needed was the right (wrong?) suspension movement to dislodge the ball joint from the bridge.
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