The rear suspension on a BMW 3.0 CS is supported by a rear crossmember
that spans the width of the car, with the trailing arms mounted to clevises
and the ends bolted to the car via rubber bushings.
As mentioned previously in the
Brace up Boys
post, the crossmember is normally triangulated by the differential, which is
mounted to the floor of the unibody, but I cut the diff mount off of the
crossmember since it is in the way of where the Tesla drive unit needs to
sit. I then fabricated a new forward-facing member to triangulate the
crossmember securing the the car. Seemed good.
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Upside down. Those tabs should be at the bottom, not near the
floor
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That is, until I went to mount the rear anti-roll bar and realized that I had
installed the crossmember upside down! Normally, this would be
impossible because the diff mount only works one way, but with that bracket
cut off, the member can be flipped and installed either way because it is
almost symmetrical. Almost.
But the swaybar mounts are near the floor, not at the bottom where they need
to be. And the trailing arm mounts are a bit off too (although they do
bolt up OK).
This meant I had to remove the entire rear suspension, cut off the fancy new
brace, and start all over again int he proper orientation. A distraction
I didn't need. The only good news is that I can now integrate the
electric parking brake system into the design of the new brace instead of
adding as an afterthought.
Tyler made the original brace very pretty, with holes for lightness. The
new one isn't as pretty but Brett and I made it so that it not only mounts the
parking brake cables better, higher, and out of the way of the swaybar, but
also so that it can be unbolted from the crossmember for easier servicing.
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Parking brake cables go through the middle now, out of the way of the
anti-roll bar
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The new brace is designed from the start for the parking brake
system. It still uses the Chevy Suburban motor mount to attach to
the driveshaft tunnel
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The new brace is a bolt-on design, located by the bolts to the
crossmember
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New versus old. Despite not having pretty holes, the new one is
actually lighter because it didn't require an add-on mount for the
parking brake system
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The bolts act as keys to center the brace on the member. Interesting
fact here: the original diff mount is NOT centered in the member. The
hole is offset by about an inch or so. Just in case you cared.
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All back together, looking forward, with parking brake actuator tucked
up high now
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| Looking backward |
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Crossmember back in the car again, with plenty of room for the rear
anti-roll bar
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Up close, one can see the Chevrolet Suburban motor mount bolted to the
floor in the tunnel
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All back together, with rear anti-roll bar and parking brakes
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