Regarding stress on the frame crossmember where the shock bracket is
mounted:
I noticed, with all installed, that when I raised the trailing arm up
with jack under wheel when the weight and spring tension were taken off
the shock that the shock tower/bracket moved back slightly and the
crossmember it was attached to moved slightly as well. I did this
several times and measured that the movement was 1/8" at the very top
end of the bracket ( thus much less torque movement on the crossmember)
and only at the moment when the weight was first removed from the
shock-at no other point in jacking up the wheel did I see further
movement, even when the car came off the stands. Since at steady state
the shock and tower are not supporting any weight and the tube shock is
nearly vertical, with changes in angle absorbed by the lower shock mount
bushings, I estimate that there isn't much if any torqueing or back
pressure on the bracket and thus on the frame crossmember. Also that
crossmember is held solid by the diff which is mounted between it and
the other crossmember and seems pretty solidly welded on to the main
frame. It was suggested by a lister that a piece of angle iron could be
fashioned that would connect between the lower mount of the bracket and
the main frame to further insure against flexing of the crossmember
caused by stress on the shock bracket. I would think it wise, however,
to check the weld at the crossmember from time to time just to make sure
no stress cracks appear, and certainly examine its health up front
before installing a tube system that attaches at the crossmember.
Regarding rubbing:
I drove about 2 ½ hours with the tube shock conversion kit installed in
all sorts of road conditions, but not to extremes. I then removed the
wheels and found no evidence of rubbing of the tire or any marks or
rubber dust on the shock tower, which protrudes into the wheel well
similarly to the upper bump stop contact, or on the shock itself.
I took measurements of the protruding part of the shock bracket ( its
upper most end) which emerges just into the wheel well almost parallel
to the bump stop contact.
The bracket protrudes 2 1/8" into the well and is 1 ¾" wide and goes 2"
down before angling away and under the trunk/boot. The top of the
bracket is 7" above and 4 ½" behind the wheel center, when the wheel is
jacked up to its normal steady state road height. This compares with
the bump stop contact which protrudes 2 ½" into the wheel well, is 2 ½"
wide, at an angle, is directly over the wheel center at the aft side and
about 1 ¾ ahead of wheel center and the fore side.
I mounted the wheel and tire and then measured the distance from the
bracket to the tire at is closest point. I have 215-65's mounted on
stock (15 x 6?) rims. The crown of the tire sidewall is directly
opposite the uppermost part of the bracket when jacked up to where the
car is just coming off the stands, ie at road steady state. The bracket
at this closest point is 1 3/16" from the tire. The bump stop contact
point is 1 3/8" from the tire at its closest point, for comparison.
I removed the road spring and then jacked up the remounted wheel and
tire (under the tire simulating any pressure effects on tire shape)
until the shock was fully compressed, ie at bump stop height and
measured the distance from the bracket to the tire. At this point the
distance was 1". Keep in mind that as the tire raises and moves inward
at the top, the side of the tire is curving outward toward the wheel,
and as a result the distance is for the most part maintained at a
constant between the tire wall and the bracket. Since most people seem
to run 215-65's, 205-70's and skinnier OEM type redlines on stock rims,
rubbing is not going to be a problem for these set-ups, based on these
observations. Installing zero offset 15x7 panasports with 215-65's,
which seems to be the standard aggressive upgrade, doesn't seem like it
would be a problem since at a minimum there is 1" of clearance, and at
the most, the additional 1" of rim width could not add more than ½" of
tire wall width on the inside, though in reality probably less. 16x8
Panasports could possibly be trouble but more rim diameter and different
tire profile could make up the difference . Shorter comp springs would
lower the profile a bit but that would seem to effectivelyy move the
bracket protrusion further down the tire wall and thus actually increase
the span between the tire wall and the bracket.
continued in next section....
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