You might expect an off-road-prepped truck with eight-wheel drive to be able to go just about anywhere, but this clip of hardcore rigs engaging in a treacherous rally proves otherwise. Just because your machine has double the driven wheels of a normal rock crawler, doesn't make getting stuck an impossibility.
This array of customized eight wheelers come from European brands like Mercedes-Benz and Tatra. They all feature external roll cages and stripped down bodies. Locking differentials let the drivers select which axles to power, but they generally keep the torque spinning all the tires.
Even with four axles turning, soft earth appears to be these big rigs Achilles heel. With enough of a run, these tuned trucks have no problem with steep hills, but their weight causes the tires to dig into the sand. It's probably best to have two of these machines around, so that there's always someone to pull out the other if a driver gets wedged into the dirt.
Where these trucks excel is on the boulder course. These are some seriously big rocks, and they're loose enough that the rigs push them out of the way when rolling over the pile. The skid plates come in handy on this course, but the eight wheels of power and significant axle articulation make relatively easy work of this challenge.
While we only see these machines from the outside, the big windows and cab-over-engine layout make seeing the drivers fairly easy. These folks are working seriously hard at the wheel to get these hardcore off-roaders over this treacherous terrain. There's also a co-driver on-board who is presumably providing extra input about the course and maybe offering a little moral support, too.
Source: K4 Movies via YouTube