Why is Mercedes 4 x 4 awesome? 3 Points to Explain It

The Mercedes-Benz G550 4 x 4($227,300), 4 x 4 Squared for short, stands 7 feet, 4 inches tall. Despite being six feet tall and lanky, getting into the cabin was a chore: I had to raise my feet higher than I would normally accept, grab the steering wheel and pull myself into the plush driver's seat. No doubt there are some obvious, diamond-studded differences for semi-truckers entering their trusty steed. Like the semi-truck, the 4 by 4 is taller and wider than almost everything on Manhattan roads.

But while the truck, based on the Mercedes-Benz G-class "Gelandewagen," is strangely perfect for big cities, it truly belongs in the wilderness. After all, this huge SUV is capable of driving over terrain that 99% of the "off-road vehicles" on the market cannot reach. This ability, most evident in its extreme ground clearance, is possible thanks to an old-fashioned mechanical marvel: the portal axle. Here are four things you need to know about the door axle to appreciate the Mercedes-Benz 4 x 4 Squared. 

The portal axle connected indirectly to the wheel assembly

In most vehicles, the axle -- the axle between opposite (front, front, rear) wheels -- is essentially an uninterrupted component. At the end of a conventional axle is a hub, a geared drive system that converts the axle motion at a 90-degree angle, thus allowing the wheel to turn. It's a straight system.

In a portal bridge, the axle is located above the hub. At the end of the axle is a more sophisticated gear system that transmits movement down to the hub, an extra step that keeps the axle higher than the center of the wheel. Essentially, the portal axle rotates in a higher plane than the wheel, which allows, among other things, a higher overall ground clearance.

Higher ground clearance enlarges a portal axle’s capacities in off-road situations

The obvious inherent benefit of portal axle mounting is more ground clearance. The axle-an intact horizontal axle-is raised above the mechanism that controls each wheel so that the lowest point in the center of the vehicle is higher than normal. That's the case with the Mercedes-Benz 4 x 4. It can lift to 17 inches from the ground, compared with 9.5 inches above average for the current "normal" Mercedes-Benz G-Class.

The AM General Humvee, the U.S. military's long-serving wartime vehicle that is now iconic and outdated, was designed with a similar system in mind. Its helical gear reduction hub allows for top-mounted portal axles, providing an additional 16 inches of ground clearance. Coupled with the Hummer's protruding central drive portal axle (which, coincidentally, is at least partly responsible for the Hummer's truly enormous width), this allows for extreme capability in off-road situations. It's worth noting, though, that the Mercedes-Benz 4×4 system adds an inch overall.

Improved torque suits a higher clearance more

Simply put, the portal bridge setup allows less work in the differential and portal axle mechanism to translate into more torque at each wheel. The half portal axle can rotate at higher speeds but produces less direct torque, which means less work at the beginning and more productivity at the end of the machine. As a result, the differential can be smaller, thus further increasing ground clearance, which combined to provide a more comprehensive off-road capability.