Can a Mercedes G-Wagen actually climb a 100 percent grade?

Since its inception in the late 1970s, the Mercedes-Benz G-Wagen has been an extremely capable off-road SUV. And even when the big bruiser was redesigned for the 2018 model year, the G-Class didn’t lose any of its off-road swagger. In fact, Mercedes claims the latest version of the G-Class can climb a 100 percent grade. But can it?

That’s the question Jason Fenske of Engineering Explained tackles in his latest video. But before we get to Fenske’s fact-checking Mercedes’ claim, we should probably define what a 100-percent grade is.

Although it seems logical that a 100-percent grade would be a vertical surface, that’s not the case. Grade is a function of rise over run, so a 100-percent grade is equal to going up a 45-degree slope. Not quite as impressive as the ability to scale the side of a building, but impressive nonetheless.

In order for a vehicle to climb a 100-percent grade, it needs three things: power, the correct center of gravity, and the right amount of grip.

With a twin-turbo 4.0-liter V-8 and a two-speed transfer case, power isn’t an issue for the G-Wagen. And, despite its tall, boxy shape, the G-Class also passed the center of gravity test—it carries its weight between its wheels and fairly close to the ground. That just leaves the question of grip.

In order to fill in this unknown, Fenske uses a braking test to find the coefficient of grip of the G-Wagen’s tires. If he can get the Mercedes SUV to stop from 60 mph in 120 feet, or from 30 mph in 30 feet, the G-Wagen’s tires have the necessary 1G of grip to scale a 100-percent grade.

Fenske ends up getting very close, but not quite to, those magical stopping numbers. The G-Class stopped from 60 mph in 130 feet, and from 30 mph in 32.5 feet, netting 0.925g.

Unfortunately, it was just after that braking test that Fenske learned his data was irrelevant. The G-Wagen he tested was rolling on a set of aftermarket off-road tires rather than the stickier Pirelli Scorpion all-seasons that were equipped from the factory, so his calculated coefficient of grip wasn't relevant to test the veracity of Mercedes’ 100-percent grade claim.

However, Fenske surmises that the factory Pirelli tires would have netted at least 1G of grip in his braking test. That assumption is backed up by the fact that Mercedes has previously demonstrated the G-Wagen climbing a 45-degree hill.