Low pressure was indeed a major culprit in this mess. Ford, themselves, are the ones who recommended the lower PSI because their models showed that the Explorer would be more likely to rollover at 35 PSI. The recommended 26 PSI was already very low, and with a propensity to lose 2 PSI a month, the possibility of getting to dangerously low PSI causing tread separation, and therefor the possibility of a rollover.