Introduction
This week’s roadtest contender is the Renault Kerax 6x4 tractor, a no-nonsense, heavy-duty tractor aimed at the uncompromising muckaway and heavy-haulage sectors. This is a rugged machine, punted squarely at the niche market dominated by the likes of Foden and Mercedes. If the Kerax is going to snatch a slice of this cake it will need to put in a high-class performance.
As regular readers know, tractive units are usually tested around our Scottish test route. However, 6x4 tractors are not best suited to this route and they’re not often to be seen tramping up and down the UK on long-haul work. Instead, we opted to take the Kerax, coupled to a short tipping trailer, around our Midlands tipper route where the new Renault could be evaluated more effectively.
Product Profile
Take a look at the Kerax and its mission is immediately apparent. The straight-beam front axle means a high-mounted cab and plenty of ground clearance – 378mm to be precise – while the double-reduction back end ensures the gearing is right for heavyweight applications. Robust 300mm chassis rails give the Kerax the beefy appearance you’d expect for this sort of application.
Riding on hefty steel suspension front and rear we were never expecting pothole-flattening riding comfort from the Kerax double-drive workhorse. But while we were ready for a hard ride we didn’t expect it to be quite so bumpy – the constant bobbing of the cab got a bit tiring after a few hours in the saddle. ‘Twas ever thus with steel suspended double-drive bogies, particularly with the tipping trailer set so far back over the kingpin, although we’ve driven more comfortable 6x4 tractors recently.
While ride comfort may not be one of the Kerax’s strong points it scores highly in a number of other areas, not least road handling where it sticks to the road and gives a very assured drive. The steering set-up is nicely weighted and the handy sized Renault steering wheel makes for easy manoeuvring. In general, 6x4 tractors have a tendency to understeer, particularly when in tight spots. Thankfully, the Kerax doesn’t seem to suffer too badly in this area, which was particularly helpful when inching through the buttock-clenchingly tight roundabouts in the centre of Buckingham.
Productivity
An overall fuel figure of 5.46mph tends to send the bean counters running for cover. But before we get too carried away in condemning the Kerax as a fuel guzzler let’s hear a plea of mitigation.
First, the test was carried out in very high winds. Second, the outfit has the aerodynamics of a housebrick. Third, this rig is built primarily fir off-roading with a very short rear axle so the engine is spinning at 1,600rpm to hold 85km/h. And fourth, 5.46mph isn’t that bad in the first place.
Before you start sniggering, let’s qualify that last point. It’s not that bad if you consider that our test route is designed to be a toughie, and the fact that the Kerax was freighted to a full 44 tonnes – the first time we’ve tested a top-weight artic on this route.
And remember the Kerax’s substantial 27.58-tonne payload. Multiply that figure by the fuel economy and the productivity rating of this 44-tonne outfit works out at 2.4p per tonne/mile, compared with 2.6[ returned by the Volvo 32-tonner we tested last December.
On bare fuel economy the Volvo enjoyed a whopping 28% advantage over the Kerax. But factor in the payload and the productivity benefit shifts to the Renault by some 7.6%.
Assess the Renault against the more fuel efficient Daf 75CF320 tested in June 2000 and the results are equally encouraging for Renault. Here the Daf enjoyed a fuel economy advantage of no less than 45%; but the Kerax payload slashes the productivity difference to 12%. Maybe the Kerax isn’t such a fuel guzzler after all.
But fuel economy will never be the strong point of a 6x4 tractor – its virtues will always come to the fore when venturing off-road.
We haven’t been able to put the Kerax through its paces on-site this time, but close examination of the chassis indicates that it shouldn’t be too inconvenienced by muckaway sites or quarries. There’s a clear foot of ground clearance under the rear bogie and more at the front, while the steel bumper, grilled headlights and hefty sump-guard are set to afford effective protection.
