Hope you can answer my question. Here’s the break down…
56 chevy truck.
This truck has been completely disassembled and reassembled.
A 3″ drop front straight axle was installed.
The original caster shims were reinstalled but the truck had bad bump steer (2 deg).
Took it to an alignment shop, they added a 4 deg shim which brought caster to +2, bump steer still unacceptable…
So I am installing new front springs, as they were the originals, and putting in 8 deg shims…
Here’s the problem.
The spring center bolt “locator pin” does not reach the locating hole on the axle AND….the spring “saddle” on top does not reach far enough out to catch the U bolts because of the angle of the axle, to reach the saddle the U bolts are angled.
Question #1: How important is the spring saddle?
Question #2: Can U bolts be used that are flat where they contact the spring?
I know I need to get new u bolts.
Question #3: Are there center bolts available that will reach thru the shim?
Let me know if you need more info, or I can just call.
I think you are going about solving your problem the wrong way.
No amount of shims will correct your incorrect steering geometry.
I think you need to take a good look at the relationship between the drag link and pitman arm as the suspension moves up and down.
Ed Stevens writes a very good in depth article as to the cause and cure of straight axle bump steer: here it is over at Naxja.org.
He explains it much better than I could.
But to answer your other questions, the spring saddle is very important.
While u-bolts can rest directly on the spring’s main leaf, and they do on some vehicles right out of the factory, stress risers can form where the u-bolts hit the plate.
A saddle, even a thin one, separates the axle from the u-bolts stopping any stress risers.
We do have center bolt head extenders.
They are sleeves which slide over the center bolt and come in varies sizes for different center bolt diameters.