It is different for every jeep. You need to have enough bump stop to keep the tire from rubbing. Once you figure out your bump stops, take your bump stop height and add 38cm. For instance if you added 5cm bump stops, then you will have 43cm between the upper and lower shock mounts at full compression. Then buy a shock with a 43cm or less compressed length. If you have more than 2-3cm of shaft showing at full compression, your shocks are too short. If you have zero shaft showing at full compression, your shocks are too long. How much shaft is showing at ride height is not relevant to anything.