Keith D,
The Explorers actually come from the factory with "passenger" designated tires. Even the optional all-terrain tires are "P" designated. In theory a replacement tire should be of the same designation as the factory offering. The choice by individuals to go to an LT tire is purely individual preference/need and by no means a pre-requisite. Tell your friend that if he wants to save his money, get a cheap set of replacement "P" tires, thats all he needs.
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Cheers,
Andrew B.
1996 Ford Explorer 4x4 (slightly modified)
BC, Canada