ROAD TEST: MERCEDES-BENZ UNIMOG & ZETROS

Reviews

Mercedes-Benz has an impressive range of off-road trucks with Unimog and Zetros, and while the latter is (currently) unavailable in the UK as it’s Euro 5 only, the Unimog is the king of off-roaders.

You might think there isn’t an awful lot of terrain in the UK to warrant the need for the ultimate in off-road trucks. And while you are perhaps unlikely to ever face the terrain of Africa, South America or Asia, there are still some instances where a decent off-roader is just what you need.

If you need to head off the highway, Mercedes-Benz has the answer. Well, in fact it has two answers: the ever versatile Unimog, and the equally impressive (and larger, more truck-like) Zetros.

We’ll come on the Zetros later, and start with a look at the Unimog. It’s probably fair to say most readers are aware of Unimogs, but not that many will have had the joy of driving one. Fot those not overly familiar with them, here’s a brief overview.

Unimogs are trucks, but they are (pretty much) go-anywhere trucks with all-wheel drive and amazing off-road capabilities. Mercedes has been building them for 70 years – it even has a museum devoted to the machines.

They have applications in the utilities, county council, agriculture, emergency services, humanitarian aid and road/rail markets. Of course, not all of those are applicable in the UK, but some are – and in those aforementioned rural areas, a Unimog is a serious proposition.

Unimogs are 4×4 and usually have a pretty short wheelbase. However, they can run on normal roads at the same speed as a normal truck (56 mph). This means they are ideal tools for moving between worksites – they don’t need to be transported, and nor do they bimble along at 30 mph on the highway like a typical agricultural tractor. Their closest ‘competitor’ might be a JCB Fastrac, but that’s still a tractor and has no body, plus a top speed of only 50 mph.

Of the Unimogs available in the UK, there’s a choice of two cabs, and two engines offering five outputs ranging from 156-299 bhp. They can gross at up to 14.5 tonnes on their own, but can also haul trailers at up to 36 tonnes GVW.

Unimog options

The two engine options are the 5.1-litre four-cylinder and the 7.7-litre six-cylinder engines, which they borrow from the Actros and Antos ranges.

The former comes in 156 and 177 bhp outputs, and the latter in 231, 272 and 299 bhp outputs. Torque ranges from 650 Nm in the lowest output right through to 1200 Nm for the 299 bhp engine.

The cabs are the UHE (Ultra High Mobility/Off-road) version on the U4023/5023 models, which is more wedged and utilitarian in looks. Then there is the newer, smoother and more aerodynamic UGE (Implement Carrier) cab, which looks a little more truck-like and is available on the U216 models through to the U530. (As an aside, there is a U20 version without a bonnet, but this is not available in the UK.)

Put another way, the UHE cab is most likely more for humanitarian aid and army spec customers, and the UGE is more likely to be bought by utility companies and county councils.

The Unimog can drive with a 43 degree angle of approach and 41 degree angle of departure, and it has a turning circle of 16.4 m. The standard depth of water it can drive through is 0.8 m, but it can be specified for working at depths of up to 1.2 m. The smallest tyres are 365/R20, and it can go up to a biggest tyre size of 455/70R24.

Unimog: Off the road

The test track Mercedes had laid on for us was extreme to say the least, and being used to demonstrate the full potential of the Unimog meant there were examples of terrain you’d realistically never drive over. The really tough stuff was for demonstration only, and the route Trucking got to drive was therefore relatively conservative in comparison.

However, it was still challenging, and took us over tracks you’d never get any typical road-going truck to tackle. It was full of steep inclines, tight curves, mud, gravel, deep puddles and woods.

The truck we had charge of was a Unimog U5023 with the ‘classic’ UHE cab. It’s basic inside for sure, but it had room for three people. With three adults in the cab, it’s certainly cosy and there’s not a lot of room for bags and the like; but again, this is most probably not a requirement for this vehicle. Crew cabs are available if you need more personnel or room on board.

The truck has an automatic gearbox, but you can drive it in manual – which our hosts recommended was best for this kind of course. Starting off in second gear on the flat, we soon found shifting up and down was a necessity, and luckily there were no awkward shifts using a long and sometimes unresponsive gear lever, instead you use a paddle on a stalk close to the steering wheel allowing you to have better control of the vehicle.

And the system works well: you get good control and are able to keep a close control of the vehicle on the move. The maximum we got to was third, but most of the route was spent in second, with the occasional downshift to first for a standing start on a steep incline.

Zetros

Now, before we get too carried away, it’s currently not possible to buy a new Zetros in the UK because it’s only currently available at Euro 5. It could be an ideal tool for the army – and we doubt the army would have to meet emissions legislation – but at the moment, it’s not an option for UK operations.

Despite this, we were really looking forward to driving the Zetros. It’s a brute of a truck and it just looks, well, mean! It looks ready for business – and dirty business at that.

The Zetros has more of a truck feel to it compared with the Unimog, which has that borderline tractor (as in farm tractor) feel to it. There were two vehicles available to try: the 4×4 1833 and the 6×6 2733.

The Zetros has amazing off-road capability and was able to do most (but not quite all) of the tasks the Unimog demonstrated before it. But the Zetros has a higher payload capacity. It is a perfect truck for military and armed forces, and also for humanitarian aid. It can also have appeal for utilities.

It’s a real shame Zetros is off the table for UK operators because its OM926LA engine – a 330 bhp straight-six – is currently Euro 5 only. There was no commitment from Merc that a Euro 6 would be offered, although some of its engineers did drop hints that it could be. Until developing nations come on board for tighter emission controls, it’s fair to say there’s no rush to offer it at Euro 6. That said, it is not likely to be too difficult for Merc to enhance its Europe-wide appeal with a less-polluting engine.

As you’d expect, inside the Zetros, it’s another no-frills affair. There are three seats and the cab is big enough to accommodate a pull-down bunk in case you get caught out and need to bed down for the night – although such situations are likely to be rare. That said, the bunk is there if you do need a nap. The wheelbase was 4800 mm.

The truck we drove was the 1833 version with a short canvas body. Under the bonnet was a six-cylinder straight-six developing 326 bhp at 2200 rpm. It has a torque output of 1300 Nm at 1200-1600 rpm.

The gearbox can be a nine-speed – eight plus a crawler – manual or automatic, and it was the latter we had in the 1833 and it performed very well, despite the ever-changing and challenging terrain. There was also a 6×6 Zetros with the same drivetrain and cab – basically an extended version of the 4×4 offering a greater payload.

VERDICT

OK, there are presently very few cases to be made for a Zetros in the UK, and even if Mercedes does offer a Euro 6 version, will there be many takers? Possibly – about 20 were sold before Euro 6 came into play, with Cumbria County Council and the Stobart Group both taking examples for gritting and off-road work respectively – and they were right-hand drive trucks as well.

You could also argue a Zetros could conceivably also make a decent chassis for wrecker applications. So there could be some sales; but let’s face, not many for such a bespoke piece of kit, which won’t come cheap.

But the Unimog is in a different ballpark altogether. Between 200 and 400 are sold each year, and Mercedes is on a drive to push sales up by highlighting the vehicle’s appeal to companies who may not be so aware of their capabilities.

It’s a very versatile truck with plenty of applications for UK operators. These trucks really can do things other off-road vehicles might struggle with, and a driver is unlikely to ever feel they are in a situation they can’t get out of with one of these do-anything, go-anywhere tough beasts.

SPECIFICATIONS

Model: Unimog U5023
• Design GVW: 14,500 kg
• Chassis: 3850 mm wheelbase
• Front axle: 6400 kg capacity
• Rear axles: Single-reduction axle, 8800 kg
• Gearbox: UG 100/8 with single-disc dry clutch
• Engine: OM934 LA Euro 6, 12.8-litre straight-six
• Max power: 231 bhp @ 1450-1800 rpm
• Max torque: 900 Nm @ 1400 rpm
• Smallest tyres (tyre/rim): 365/80R20
• Biggest tyres (tyre/rim): 455/70R24 

Model: Zetros 1833
• Design GVW: 18,000 kg
• Chassis: 4800 mm wheelbase
• Front axle: 9000 kg capacity
• Rear axles: 13,000 kg hub-reduction axle
• Gearbox: Nine-speed plus crawler
• Engine: OM926LA Euro 5, 7.2-litre straight-six
• Max power: 326 bhp @ 2200 rpm
• Max torque: 1300 Nm @ 1200-1600 rpm
• Tyres: 14.00R20

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