in the Wrangler with 285/70/17's I only drop them to around 22 psi if just the wife and I. If I am towing the van up the beach I will drop them down to about 18 or even 15 if really soft so I dont risk getting bogged, but I dont have any ground clearance issues with it!
The threads I was reading was on a dedicated Cherokee forum,
this should link you to the page.