Originally Posted by crunchedtj99
i was looking more at articulation travel. lets say for an example what the 8.5" of travel a 6" lift shock on an xj would give me. i can do the math but more looking at what real world people have and actually think they use is
If you are looking at articulation, then the very rough rule is similar to the one above.
Articulation travel of the tire = Shock Travel * (Distance from tire to axle midpoint / distance from lower shock mount to axle midpoint).
But that assumes you have good shock geometry, suspension geometry, no tire interference, etc. Can be hard to actually achieve that. And thats assuming the axle pivots around its center, which it doesn't always. Depends how its loaded, and the links used.
For example, if a shock is mounted 24" out from the center of the vehicle, and the outside edge of the tire is 40" out from the center of the vehicle, then if you had a total of 14" of travel, then your tire could in theory move in an arc of about 23". But that depends on so many factors of the suspension design, how much up and down travel you have in the shock, binding in the steering, suspension joints, driveshaft, brake lines, yadda yadda..
Your bigger concerns will be how to fit the shocks and not have them hit anything at full stuff and droop. Especially on an XJ. Coilivers are wider than air shocks, getting them spaced out to not pull into the frame, or have the tire come up and hit them can be a challenge in an existing vehicle. Wider axles makes a big difference.