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Here's a photo of the lift overall, other than the non TJM associated part teething problems, I can say that I'm really happy the way the Cruiser handles on the 315's. Firm but not harsh and quite stable. The lift is a little lower in the back I think, (haven't actually measured it yet) but I don't have any weight up front. I have an ARB winch bumper in my shop waiting to go on which will eventually have a winch installed. It should be fairly level once the weight is on the front end, which will be great if it means not adding spacers. Fingers crossed.
landtank said:I'm not sure why people seem to think you need longer arms with a 4" lift.
In stock form the center of the axle is 2" higher than that of where the arms bolt to the frame mount.
Assuming a 4" springs yields 4" of lift then the axle is now 2" lower than the frame mount.
So comparing the axles position vertically they are exactly the same. They are just at the opposing sides of zero.
This was one of the design considerations when engineering my caster plates. I wanted a plate system that would retain the axle's position on the arm. That was achieved by relocating the holes on the axle bracket to only rotate the axle.
Attached are a couple of pics taken just a few minutes ago of a stock truck sitting in my drive way.
Jake40 said:Looks like you're running front bump stop spacers. Remove and problem solved.
Jake40 said:Alright I'll rephrase then. Contact between the spring and bumpstops is common on lifted 80's running stock control arms and dropped bumpstops. If the axle is square under the truck, the caster is within spec, and lift is uniform in height, then I personally wouldn't worry about the visual difference of the spring from left to right. I would simply remove the bumpstop spacers, as many have done before, and enjoy my truck with far less money invested than the alternative options that have been discussed. Just my opinion. Ignore if you'd like.
Rusty said:You can draw an imaginary line between the two points either side of the pivot.
It's true, if axle centre on stock suspension is 2 inches above the pivot, or frame bushing, then a 4 inch lift should drop the end of the arm 2 inches below the center of the pivot. You can draw an imaginary line between the two points either side of the pivot that would bisect an equally imaginary horizontal line at 90 degrees, or the "zero" as you mention. Of course that's really over simplification though because caster correction that maintains spring alignment requires rotating the axle while keeping the spring perches in line. You just can't do that with stock arms, in essence you have to extend them to be able to relocate the axle pivot point and you run out of arm to do this.
Perhaps your caster plates achieve axle rotation to correct caster by pivoting the axle further out from where my lousy Ironman plates do. Undeniably this means that you really don't have to buy arms if you are prepared to drill and alter the axle bracket holes. You either alter the radius arm brackets on the axle or you extend the radius arm length.
At this point I'd rather try to source new arms than punch a second set of holes, next to, or nearly on top of the existing ones.
kidglove13 said:Obviously this is documented problem with lifting an 80 4 inches and higher.
But for one of your springs to be that much more off than the other I would really investigate to see if something else is not the problem.
landtank said:Assuming the axle perch is sitting flat when in the stock position, once the axle is lifted the spring perch while still vertically centered is actually tilted forward.
Rotating the axle on it's center not only corrects that alignment but returns everything back to it's stock location only 4" lower than before.
A set of arms designed to do this would yield zero gains over drilling new holes in the brackets and might possibly flex less because you would need to accomplish the rotation by repositioning the bushings which I think would introduce more bind.
Good luck with your quest for new arms. I think a company called Snake Arms might have what you are looking for.
Not to perpetuate argumentation, but really, you can't.
It's not two points. Have to draw two imaginary lines, therefore it alters the length of one by rotating.
I'm not the sharpest tool, nor know how to input the radius arm into a calculator, but essentially it's a 4 link with pan hard and by increasing the distance of the vertical plane (lifting) it only makes sense that it shortens one of the link lengths, considering the pivot is the same location on both.
Right?
...Of course that's really over simplification though because caster correction that maintains spring alignment requires rotating the axle while keeping the spring perches in line. You just can't do that with stock arms, in essence you have to extend them to be able to relocate the axle pivot point and you run out of arm to do this.