No apology needed on my end!
Mine is from an XJ6. I pulled it and the car looked unmodified. In fact I thought it was ashame to see it in a salvage yard...
Anyway, yes I am aware of the way it is SUPPOSED to sit. but I am not going to try and do anything about it until...as you said...get it all together and then deal with it. I will need to put new bushings and whatnot, on the IFS as well. I do know that the XJ12 has stiffer springs than the XJ6.

 

Jeff- Ax - I really respect your knowledge and willingness to share info regarding the Jag convert- Jeff you have helped me in the past --- I have the XJS in and just finished putting in the front braces using your model Jeff. Worked very well-- Question is what happens if the control arms are NOT parallel to the ground?

 

As I said, it throws off the designed geometry. The further from parallel the worse it will handle. It's more noticeable with a high centered top heavy vehicle like our trucks than on a stiffly suspended low slung vehicle like my Solstice. Many "baggers" have found out the hard way that their vehicles are completely undrivable when dropped or raised very much from stock. I can explain what happens if you want to do a lot of reading.

 

Thanks - I just wasn't sure what you meant by that and better safe than sorry. I wouldn't mind reading any info you have as it only helps and you seem like a very knowledgeable guy regarding any of this suspension stuff- I really appreciate your expertise and willingness to share it as I am sure others do too. Anything to make this F3 safer is good by me. The reason I am putting in the Jag IFS is the Mustang just didn't feel safe going over 50 and maybe all I had wrong was the setup. Thanks again Dave S

 

Without getting into the geometry issues, yes adding spacers under the lower arm and above the spring plate will lower the vehicle. It is kind of like a shorter spring, but you have the same as stock spring length, but a longer distance for it to fit. So the spring is still the same compressed length with load, but the lower arm is raised up the height of the spacers at the spring location. Since the inner pivot is the same, and the spring is approx halfway, the drop at the spindle is about twice that of the spacer. In other words, a 1 inch spacer will result in about 2 inches drop.

I agree that the lower arms parallel to the ground is best, and meets the design intent. if you want to get really low, then you should mount the suspension assy higher up realtive to the frame to start with. That way you maintain the geometry as designed.

 

OK now you are trying to confuse and old man! I don't want to hijack BARRNONE51's questions but I really want to do this right and hope these questions make sense. I don't want to lower the ride- I like it high to see over all the silly pretty new 10,000 pound SUV's out there that look alike!. So as long as the arms are parallel I can put 15 inch or 17 inch wheels on it with springs from an XJS or XJ6 or whatever and it should work pretty well. Thanks for all the info and I hope BARRNONE51 isn't mad at me. Dave S

 

Dave, the wheel diameter (and tire type, wall height and stiffness) will have some affect on the geometry, but not a great deal unless you go overboard (22's or similar) or are doing a lot of hard cornering. You can adjust for wheel diameter with the tire profile. Having the lower control arms parallel to the ground is the way to go. AFA the springs for the best ride and control you typically want the softest spring that will support the weight and keep the tires in contact with the road over the largest undulations and without going into coil bind at full suspension compression.

 

You are the wizard of the suspension systems and much more - Thanks for all your help Dave S

 

Wow!! this thread really got some traction..Anyway this is some good stuff!! And 49f3dls no worries this is great info and how can someone be mad at good information.
38chevy454 have you done a jag with the spacers and how did it turn out?
I am still not going to do it till I get the truck together to see what the end result is. And one thing to remember that is the front end is kinda inportant to be done right no Joe magee!! if you get my drift.

 

To understand what happens to the geometry, you must first understand what happens when the control arm moves. To make things easier lets lock the frame height (and the inner control arm pivot point) and move the wheel up or down. Since the wheel is connected to the end of the control arm the end also moves up and down. As the arm rotates the outer pivot point (ball joint) also moves closer to and further away from frame.
The distance it moves is called the angular displacement.


If position A (horizontal purple) is our at rest position, then rotating the arm up a small amount (position B) makes only a small change in the displacement AB. The more we rotate the arm (positions C and D) the greater the angular displacement becomes: displacement AC, displacement AD. The change is not linear, but increases exponentially as the angle increases. In simpler terms the larger the rotation from horizontal the faster the outer pivot moves in or out. the outer pivot point movement is much greater when it moves from C to D than when it moved from A to B.
The same displacement change would happen if the arm rotated below horizontal, or if the outer pivot point was stationary and the inner arm end moved up and down.

In turning a corner. the frame rotates about it's horizontal center of gravity, which we call "body roll". The higher the center of gravity the more the frame tilts. When the frame tilts, the side towards the inside of the turn rises up and the side towards the outside of the turn drops down the same amount (for the sake of simplifying the discussion). If the control arms were parallel to the ground at the start, the wheels would both move towards the frame the same amount (same angular displacement), and the truck would continue tracking the same, NO PROBLEM!
But what happens if we lowered the truck by shortening the springs? Both control arms are angled up at rest. Now when we go around that same curve, as the frame tilts the inside control arm will first move up to horizontal then will reverse it's at rest angle and start angling down. Since this change in rotation is near the horizontal position the angular displacement will be SMALL, the wheel will move in or out very little. But the outside arm's rotational angle will INCREASE as the frame tilts, so the angular displacement will be LARGE, and the outside wheel will move towards the frame much more. This will decrease the tread width on that side and the turning radius will change as the the truck goes around the turn, resulting in a handling abnormality, which is often described as the "drunken monkey effect".
So far we have only considered the affect of angular displacement on the lower control arm, when we add in the fact that the upper control arm is typically shorter and not parallel to the lower arm, and the change in displacement length of the outer tie rods, the asymmetry of the movement of the two sides become even more dramatic. The engineers designed the suspension to minimize that asymmetry by starting with the lower control arms and outer tie rods parallel to the ground.
Questions?

 

Of course there are questions it first I have to figure out if I resale understand what you said. I don't want to waste your time or show everyone how dumb I feel right now you are still the wizard thanks. Dls

 

Sorry smart phone. Hanged words resale was suppose to be really

 

Ask away! I don't know what I need to clarify if no one asks questions.
IMHO the only dumb question is the one you have but don't ask it! If you have a question I guarantee there are at least a couple others that have the same or a similar question, so think of asking as helping someone else!

PS I edited the diagram

 

After reading it a couple times it does make sense. I think I even understand why you said the wheels won't make too much of a difference unless you go to extreams again thank you I owe you sneer or two if you get to ky anytime. Dls

 

Darn phone that's beer or two