Regarding potential binding of shock and twisting of bracket/frame
crossmember due to arcing of trailing arm:
The lower end of the shocks mount in the same hole in the back of the
trailing arm as the lever arm link does. The hole is around ½ to ¾ inch
wide by my reckoning, though the tube mounting stem is only about 3/8"
in diameter. That means most of the mounting hole is filled with the
upper and lower shock mount bushings, just like the lever arm link. This
arrangement allows for the shock to "orbit" within the mount on the flex
of the rubber shock bushings. My observation was that this flexibility
should be more than sufficient to allow the shock to change angle at
that end as the trailing arm arcs upward. I installed the lower mounts
at full tightness.
I removed the road spring.
After mounting the lower end of the shock, I then jacked up the trailing
arm until the upper shaft of the shock slid through the mounting hole at
the upper end of the bracket ( the " shock tower"). I observed that at
this point the shock was nearly vertically in line with the bracket,
though slightly angled at the top toward the front of the car.
I installed the upper mount at full tightness. I then continued to jack
the trailing arm up ( jack under wheel) and observed the angle of the
shock becoming slightly greater as the trailing arm arced up. I noticed
that nearly all of the change in angle was occuring at the lower mount
on the trailing arm and only slightly at the shock tower mount,
demonstrating what I observed above, that the larger hole at the lower
mount would allow for the necessary flexibility at that end while
maintaining a constant vector at the shock tower. I went up and down
several times with the jack and the observation was consistent. It would
then appear that the shock tower does not suffer from a lot of lateral
force. I would conclude, based on these observations, that the
likelihood of binding of the shock due to the lateral movement of the
trailing arm is very low, given the flexibility of the lower mount and
the only slight change in its slight angle through the entire arcing of
the trailing arm. Keep in mind, that the trailing arm under normal road
loads only moves up and down a couple of inches ( recall my bounce
test), especially with these tube shocks, and would likely not ever go
near the maximum of the arc. I had thought of using poly lever arm link
bushings in place of stock rubber shock bushings, but the need for
flexibility precludes this idea.
to be continued in next section....
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