Mercedes-Benz G 63 AMG 6×6: Taking the desert by storm
Chassis and wheels: Automotive declaration of independence
- Axle and suspension components from the G range
- Rally-proven, adjustable gas-pressure shock absorbers
- Best possible degree of articulation
- Three-part stainless-steel underguard
- Tyre pressure control system controllable on the move
- Tyre pressure can be set to required level in record time
- Special beadlock wheels for demanding off-road use
As already described, the chassis is largely based on the current production configuration, the only difference being that the helical springs and dampers have been adjusted to take account of the changed characteristics of the three-axle model. For the springs, too, the engineers were able to draw on the comprehensive array of "G" parts, which includes no less than 15 different spring rates. Both the front axle and the first rear axle have substantially harder springs from the special-protection variant while the second rear axle has a softer spring rate.
With all three rigid axles able to move independently, the G 63 AMG 6x6 has independent axle suspension rather than independent wheel suspension. The axles articulate independently of each other, thereby ensuring the best possible frictional connection with the ground at all times. Although the two rear axles are only 1100 millimetres apart (the overall wheelbase is 4220 millimetres), they are able to assume dramatically opposing articulation angles and so make effective use of every opportunity to gain traction, even in extremely rough terrain.
Only a "G" can improve on a "G"
The adjustable and rally-proven gas-pressure shock absorbers are supplied by an external partner. Working in concert with the voluminous tyres, the chassis set-up impresses with its outstanding ride comfort combined with high driving dynamics and driving safety under all conditions, on and off the road.
The suitability of the G 63 AMG 6x6 for off-road use becomes particularly clear when its key off-road data* are compared with those of the already impressive series-production G:
|G 63 AMG 6x6||G 500 Long Station Wagon|
|Ground clearance||460 mm||210 mm|
|Angle of approach/departure||52°/54°||36°/27°|
|Tilt angle||30° (58%)||28° (54%)|
|Fording depth||1000 mm||600 mm|
|Slope climbing ability||100%||100%|
*Max. figures in ready-to-drive condition acc. to EC: Standard equipment including driver (68 kg), luggage (7 kg) and fuel tank 90% full.
If, despite all the driver's efforts and the outstanding ground clearance, the chassis should accidentally come into contact with the ground, the developers have had the foresight to equip the vehicle with a robust, three-part underguard in stainless steel. This ensures that the most important assemblies at the front and rear as well as those in the underbody area between the front and rear axles are well protected from impacts and hefty knocks.
"...and major variations in air pressure are expected to occur rapidly..."
The design of the tyre pressure control system is in keeping with the high technical standard of the G 63 AMG 6x6. A system that is a familiar feature of many trucks is being used in a passenger car for the first time. From inside the vehicle, it is possible for the driver to adjust the tyre pressure on the front axle and both rear axles independently at any time by means of switches on a special overhead console. Pressure gauges allow the pressures to be monitored. This means that the occupants are spared the usual laborious process of getting out and adjusting the pressures manually. Thanks to a powerful compressor and four 20-litre compressed air reservoirs fitted at the sides in the rear wheel arches, the tyre pressure can be adjusted in possibly world-record time. For example, although there are six voluminous tyres with a diameter of one metre each, it takes the system under 20 seconds to increase the sand-friendly tyre pressure of 0.5 bar to the 1.8 bar required for on-road use. Conventional systems take around ten minutes to achieve such a change in tyre pressure.
The design of the portal axles also has a very positive effect where the tyre pressure control system is concerned. Unlike the situation found where conventional rigid axles are fitted, the inner faces of the wheel hubs are exposed and the installation space is not blocked by the drive shaft. This means that the tyre pressure adjustment can be carried out directly by means of a central channel in the wheel hub. The wheels also have an air channel and are connected to the hub via a compressed air hose with a quick-release coupling to enable a wheel change, if necessary. A strong, bolted hub cover protects the hose connector from damage in off-road terrain.
Despite a kerb weight of 3850 kg: Ground pressure distribution as low as a human footprint
With the usual wheel/tyre combinations it is impossible to reduce the tyre pressure to 0.5 bar for driving in sand. 1.0 bar is normally the lowest possible pressure, below which tyres may come off their rims during steering manoeuvres and sand can enter the sealing surface between tyre and rim, resulting in a slow puncture. There are no such problems with the G 63 AMG 6x6 which is equipped with special, two-part 45.7 cm (18-inch) beadlock wheels. When a tyre is fitted to this type of wheel, it is clamped between the wheel (formed by the two halves of the rim) and an internal beadlock ring so securely that, even in the event of a complete loss of pressure, it cannot slip off the rim and sand cannot enter.
The extremely low tyre pressures increase the contact patches of the 37 x 12.5 x 18 inch all-terrain tyres and provide considerable support when it comes to making progress on loose surfaces. Two processes contribute to this. First, the increased contact patches reduce the ground pressure and thus the tendency of the tyres to sink or dig into the ground. A look at the figures brings this home: reducing the tyre pressure to 0.5 bar increases the contact patch threefold. As a result, the ground pressure of the G 63 AMG 6x6 with a ready-to-drive kerb weight of 3850 kilograms is equal to that of the footprint of a person of average weight.
Second, on muddy and similar surfaces offering better contact, the low tyre pressure supports the self-cleaning process which prevents clogging of the tread pattern and so ensures that the best possible traction is always available.