Rock Crawler Tackling the Trail

About this drawing

A 4x4 rock crawler looks like it is defying gravity, but it is all mechanics. The key is four-wheel drive: the engine sends power to all four wheels at once, so if one lifts off the ground, the others keep pushing.

These rigs also have a low-range transfer case, which multiplies torque in exchange for very slow speed. On rocks, drivers creep along barely faster than walking, controlling every tire. Many also use locking differentials, which force both wheels on an axle to turn together even when one is in the air.

Lifted suspension lets each wheel travel far up and down on its own, wrapping the vehicle over the shape of the rocks. Big tires with deep lugs grip better, and drivers often let some air out so the rubber flattens and hugs the stone.

Rock crawling is popular in places like Utah and Colorado, where famous trails cross bare rock. Drivers stick to marked routes to protect fragile land, travel with at least one other vehicle and rely on a spotter who walks ahead and signals where to place each tire.

• rock crawler
• 4x4
• off-road
• adventure
• trucks