Rockcrawling

Rock crawling is an extreme form of off road driving using vehicles anywhere from stock to highly modified to overcome obstacles. In rock crawling, drivers drive highly modified four-wheel-drive vehicles such as trucks, Jeeps, and "buggies" over very harsh terrain. Driving locations include boulders, mountain foothills, rock piles, mountain trails, etc.

Rock crawling is about slow-speed, careful and precise driving, and high torque generated through large gear reductions in the vehicles drivetrain. Rock crawlers often drive up, down and across obstacles that would appear impassable. Such vehicles to rock climb are primarily 4x4s.

Rock crawling competitions range from local events to national series. A rock crawling competition consists of obstacle courses that are about 100-200 yards long. Each obstacle is set up with gates, similar to a ski course.

Vehicles commonly used include Jeep (the Chrysler and the Mitsubishi Varieties), Lada Niva, BAW, Nissan Patrol, Toyota Hilux, Toyota Land Cruiser, Land Rover, Mercedes-Benz G-Class, Santana PS-10, Ford Bronco, Suzuki Samurai, International Harvester Scout and especially the Mercedes Unimog due to its portal axles and greatly increased ground clearance. These vehicles are outfitted with custom parts. Power is usually not an issue, as rock crawlers typically lower their gear ratios in order to drive more slowly over obstacles without stalling the engine. These custom parts can include:

Oversized, low-pressure, knobby, mud-terrain tires are used. Most vehicles have a low-geared transfer case to make the most torque in the low speeds used for rock crawling. Suspension-wise, rock crawling vehicles sometimes have after-market lift kits installed, raising the chassis and increasing suspension flex, though the rock crawlers running the tougher trails often have fabricated suspension systems, or home-assembled leaf packs to cheaply achieve the goals, making it easier to drive over larger obstacles with less risk of damage to the vehicle. Most suspensions are made to be highly flexible, allowing for the maximum amount of tire area to contact the ground, while keeping the vehicle as low as possible. Due to the conflicting nature of the dynamics and needs of rock crawling and highway driving vehicles, it is not unusual to modify a vehicle solely for off-road recreational usage.

...
Wikipedia