How to tell if leaf springs are worn out

Mine sit just about flat and my lift shackles just about touch the rear bumper. Should there be some arch to these when sitting on level ground? I am guessing mine are worn out.

Even when they're good the XJ springs don't have an even arch, with a portion even negative, so I wouldn't go by appearance, but by ride height. It might be possible to search archives here and find some reference for the correct height, but for starters I'd just put the vehicle, unloaded but with a fairly full tank, on level pavement, and see what it looks like. It should be a tiny bit up at the back. If it's down at the back, your springs are sagging. It's a common condition for XJ's, so they probably are. If you're looking for a cheap quick bandaid, check archives again and see if you can scare up some posts on adding a leaf. Several of us have done this in different ways using leaves from another XJ pack.

There are several threads stating that a quick check is to measure from the center of the wheel perpindicularly to the bottom of the fender flare. The distance should be 17 (+ 1/2?) inches. When looking at my XJ, the front wheels seem to sit a bit above the rear. However, when I measured from the center of the wheels I came away with 16 5/8" (driver side) and 17". (There is an apparent list towards the driver's side when looking at the lift gate.) I do need to replace the rear shocks, and will take another look after that is completed.

Most XJ's sag on the right side because of the torque on the rear axle from that huge 190 horse, 4.0 they put in them. I have a 3" skyjack and spacers on my 93, and the lift is only two years old and it is about 1/4 - 1/2 lower on the right side.