I’m building a 1931 Model A Coupe on Deuce rails with a Lincoln Versailles 9” rear. I’m having trouble figuring out where to mount my upper bars due to the housing is not a centered housing. So one of the bars wants to run up the center section of the housing and the other is on the axle tube…?
@30fordcoupe They will need to be mounted at the same height off the diff tube, and at the same angle as viewed from above, or they will trace different arcs as the suspension cycles. In other words, the bars on each side need to be symmetrical but reversed, if that makes sense. Make the mounting bracket/tabs in the second pic longer so the bar attaches at the same height as the first pic. You may want to add some extra gussets to the longer tabs on this side to strengthen them. Quick question.... Are you setting up your suspension with only the frame supported by the coilovers? Ride height should be set up with a solid bar of the desired length instead of the coilovers, and then the coilover spring rate matched to the finished vehicle weight. Not criticising, just checking.....
As above, you will need a longer mount of the tube and shorter mount of the pumpkin to keep bars same height. My thread has pics of how I done it, but there is heaps of threads about triangled 4 links. Glen
You are half way there by simply using a string line. You need to extend the string line further rearward [down the centreline of the car] The upper control arms can be less "triangulated" this simply moves the roll centre further rearward behind the rear end. If you also string line the upper control arms, THEY BOTH must intersect at the same point on the centreline of the car. [this is only from a birds-eye view, and doesn't dictate roll centre "height"] Once you have this located [centralized] then custom make brackets to fit the offset of your rear-end.
Here is triangulated rear install by @grdra1 https://www.jalopyjournal.com/forum/threads/my-new-ride-finally-on-the-road.1113909/page-3 Starting at post 73.
Imagine the rear susp. as it rolls over a stone. You may intuit the motion(s). Really need to intuit→model→prototype Out of stiff cardboard.
While you can fix the issue by having different frame brackets and such, the best fix would be to center that housing or get a centered housing the correct width.
I ran into the same problem on the 9 inch in my '62 Merc. The mounting brackets to the diff housing will be different from side to side on an off-center housing. Cut and grind as needed. The geometry of the bars as explained in the posts above is what is critical.
Not sure what your rear brake plan, but if you went with the Versailles housing for the disk brakes do some checking around. They were a thing in the 70s when there wasn't many options with parking brake. The calipers are heavy and the parking brake is, to be polite, troublesome. If you want a Ford disk brake rear with a good parking brake look at the early 90s Explorer.
Find the center of the frame and measure left and right the same distance. It does not matter where the center pumpkin is at, only that your mounting points on the rear end be the same distance from the center of the frame. Then make brackets that suit those mounting points and keep the pivot points at the same height. It doesn't matter where the center of the pumpkin is located, its the center of the whole housing that you should be working with.
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