ShutterBug

The point was to predict it.

Rednroll

14Sport the image you posted helped me to figure out how to solve this. I just needed to identify all the known variables, unknown variables, then identify all the equations that apply. Then you just need to take all that and do some Algebra.



Equations:
A^2 + B^2 = C^2

D=Lift Height

E=B+D

F= A-X

F^2 + E^2 = C^2

You need to know variables A, B, C and D, where D is your added lift amount, then once you have all those values you can solve for "X" which is the shift amount. Since "C" the TB length, doesn't change we just needed to add another pythagorean theorem equation additionally using the lengths 14Sport mentioned changed and to include the constant variable "C".

Once you get all those variables solved, then we can throw an additional adjustable TB equation into the mix and figure out what the length of the adjustable TB should be to get the axle re-centered.

Y=New TB length.

A^2 + E^2= Y^2

Solve for Y for new TB length.

14Sport

Obviously the math is fresher in your head than mine.

Knowing A before you messed with it becomes very important then since that is what you want to get back to.

I took the easy way and just marked my axle with a laser before starting.



I do, however, think it is likely a prediction could be made. Like Ron said, each Jeep will have it's own individual starting point based on ride height. As the track bar flows through its arc, the ratio between lift and shift change. At the top of its arc, say horizontal, changes will affect lift much more than shift. At the middle of its sweep, 45 degrees, lift and shift will be nearly equal. And at the bottom of its arc, vertical, changes would result in more shift than lift. So if I'm thinking correctly, a table could probably be created using lift and track bar angle to predict shift.

karls10jk

Now that we're bringing "stock" and calculated "lifted" measurements into this, it's important that we all measure from the same spot.....link below.

JK Stock Curb Height Measurement

TheDirtman

The change along an arc is not linear it is exponential. the more the angle of the track bar the more the axle will shift.

zstairlessone

Use an angle finder to find the original angle of the track bar from horizontal

Measure the length of the track bar

The cosine of the angle times the length of the track bar will give you the initial position of the track bar end along a horizontal axis from the pivot (write this number down)

The initial height of the pivot point of the track bar will be the sin of the angle times the length of the track bar

The new height will be the original plus how much the tip of the track bar will be lowered

The arc sine of the new height divided by the track bar length will give you the new angle

The cosine of the new angle times the track bar length is the new position of the track bar end along a horizontal axis from the pivot

Subtract this number from the one in step 3 to get the horizontal distance the axle moves from your expected lift.


It will be different for each vehicle because the starting angle will be different, they may be close from stock to stock, but any weight added or removed from the vehicle will affect spring sag and change the initial angle.

TacticalTankJKUR

Correct but I would've just called C "TB" and it should be clearer that F is being measured to the right angle, not all the way out to the wheel. I also prefer delta A and delta B instead of X and D but beggars can't be choosers!

I simplified the equations removing C since it is a constant and you can solve for F directly with all of the same starting info... making it easy to find X and thus TB', but I entered it all in and the post didn't go through and I was on my way home, so too bad. I can post it tomorrow at work if I remember.

jedg

Hahahaha. This is a great science project. I was skeptical at first but I think you're on to something.

14Sport

That's a valid point. Is this better with a color change outside the right triangle? TBH it was just a quick and dirty to illustrate a point.

TacticalTankJKUR

Yes this drawing is better IMHO. I would change the red triangle to A', B', and C' (or change both triangles to A1 vs A2 and B1 vs B2, etc). If you change the red triangle to primes (A' for example), my forumula becomes:

A' = sq rt (B^2+A^2-(B+Delta B)^2)

and Delta A = A-A' which gives you the shift.

If you use A = 60", B = 10" and Delta B = 2", for a 60" axle 10" stock height and 2" lift for easy math, you get A' = 59.6" and Delta A = .4"