The Ford Explorer is the sport utility vehicle category's 900-pound gorilla. And that enviable status is sure to continue now that Ford has lifted America's favorite multipurpose truck to a higher plane. The 2002 Explorer hits showrooms this spring with comprehensive changes from road to roof. Track width, wheelbase, and overall width have all been increased a couple of inches. Door openings are wider and sills are lower for easier access to the interior. Fully boxing the frame members increases their resistance to twisting. In pursuit of a smoother ride and superior handling, front torsion bars have been replaced by coil springs and the rear suspension is an independent design. The standard 4.0-liter SOHC V-6 is tuned up with more torque, and an optional 240-hp 4.6-liter SOHC V-8 replaces the 5.0-liter pushrod V-8.Inside, more sophisticated underpinnings have cleared space for a third row of seats. New are side curtain air bags that stay inflated for several seconds after a lateral collision.