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2WD OR 4WD
Under some circumstances a 2WD can outperform a 4WD.
The success of the Peugeot 2008 DKR race machine in the 2016 Dakar event has prompted some off-road enthusiasts to suggest that there may be a place for a 2WD to challenge the accepted ability of a 4WD for off-road touring. It’s not that simple.
For a start, racing vehicles are always built as lightly as possible, because the only payload capacity they need is for two crew, a couple of mounted spare tyres and enough fuel.
Peugeot hasn’t published an all-up weight figure for the 2008 DKR race vehicle, but it’s certainly a lot less than that of a loaded bush-touring vehicle
In the case of the Dakar event there are also important concessions granted to 2WD vehicles, compared with 4WD entrants.
Peugeot Sport was able to fit the DKR 2016 with suspension offering way more wheel travel: 460mm, compared with only 250mm for 4WD competitors.
Larger wheels and tyres are also permitted, along with a tyre-inflation system that allowed the 2008 DKR machines to vary tyre pressures on the move.
The 2016 race vehicles were upgraded versions of the machines that finished the 2015 race in 11th and 34th positions. Changes included lowering and widening the frame and bodywork and reducing the front and rear overhangs.
The mid-mounted V6 twin-turbo diesel engine was upgraded, with outputs around 270kW and 800Nm.
These changes bore fruit immediately, when an early version of the 2016 Dakar car took a one-two victory at the late-2015 China Silk Road Rally and the
Dakar success followed – albeit with only two of the three 2008 DKR vehicles making it to the finish line.
Hot 2WD vs 4WD competition
The relative abilities of 2WD or 4WD four-seat vehicles were compared in the European battlefields of World War II. The Germans had the 2WD Kubelwagen and the Americans had the Jeep.
The Kubelwagen was a derivative of the rear-wheel-drive VW ‘Beetle’, with an open, lightweight body and 19-inch wheels, and the Jeep was a purpose-designed military quarter-ton 4WD machine.
Changes to the early Type 62 Kubelwagens included a stronger platform frame and reduction gears in portal hubs on the rear axle shafts.
The Type 82’s reduction gears provided crawling speed that matched foot-soldiers’ marching pace and the ‘drop-box’ hubs increased ground clearance that was matched by front suspension mounting changes.
The Kubelwagen featured the first production-vehicle application of a self-locking differential, giving it much better tractive ability off road, and its flat belly allowed it to slide over sand, snow or mud. In some ditch-crossing manoeuvres it was more capable than a 4WD Jeep that could get hung up with diagonal wheel spin.
The locking diff design was first fitted to the mid-engined 1930s Auto Union racing cars, after Ferry Porsche commissioned ZF to build it.
While the one-litre, air-cooled, 22.5hp VW engine couldn’t perform or tow like a 60hp Jeep could, it was inherently more stable, on and off road, and had much better ride and handling, thanks to its independent, long-travel suspension.
There are conflicting stories about what the Americans thought of the VW. In the middle of the War official US military tests concluded that the German vehicle was simpler, easier to manufacture and maintain, faster, and more comfortable for four passengers than the Jeep.
However, by War’s end the opinion was: “The Volkswagen, the German equivalent of the US Jeep, is inferior in every way except in the comfort of its seating accommodation”.
The VW’s configuration made it easy to convert to four wheel drive, by extending the output shaft through the front of the transmission and to the front axle via a propshaft running in a central tunnel in the floor pan.
A limited number of Kübelwagen, including the amphibious version, were built with that system, but the extra expense and weight proved unjustifiable for
the bulk of Kubelwagen applications.
It’s obvious that lightweight 4WD-equivalent vehicles can be built using rear wheel drive only and in some cases these 2WD machines can outperform 4WDs.
However, the need for payload means that most 2WD machines are found wanting.
A mid-engine or rear-engine layout is essential and that’s simply not offered in production, load-carrying vehicles these days.
The last of such machines was the rear-engined VW commercial, popularly called ‘Kombi’.
Like the Kubelwagen the Kombi had portal rear axle hubs that gave it ample ground clearance for off-road driving.
Allan Whiting spent a year in a camper version in Europe many years ago and did a fair amount of off-bitumen exploring without drama. A well-driven old Kombi can still match it with some 4WD vehicles!
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