This week CM brings you an exclusive test of Renault's
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G300.26D 6x4 tipper chassis, fitted with a Neville Charrold steel body. It's more than competent and competitive in most areas but seems to be rather heavy for a vehicle in this sector.
This six-wheeler is part of the heavily revised Maxter range that was first
shown at the Paris Motor Show in October 1992. Also available are a range of 8x4 and 6x6 models with the same engine, chassis and cab combination, in day and sleeper form.
Our test truck is owned and operated by Oil Tank Supplies (OTS) of Gloucestershire. In addition to its fuel tank manufacture and installation business OTS operates aggregate transport from local quarries.
The hike in vehicle excise duty ('TED) at the newly permitted higher weights wasn't quite so bad for six-wheelers as it was for 8x4s when first introduced last year. As a result the 26-tonne 6x4 has become increasingly popular. Whatever they're taxed for, all today's trucks are engineered for operation at the higher weights.
Renault VI (UK) has no press test fleet of its own at present, hence our trial of a working truck. The K-reg machine had more than 90,000km on the clock when we tried it in early March.
• PRODUCT PROFILE
The 6x4 tipper chassis is the shortest of three day and sleeper cab variants. This is the most common wheelbase used for tipping applications with its 4,52 metre effective wheelbase and 1.35 metre drive axle spread it just meets the minimum 5.2 metre outer spread demanded by 26-tonne legislation.
The 26-tonne rules also require equal loading between drive axles or "road friendly" air suspension can be specified. Renault's solution is to use the low maintenance rubber suspension from Hendrickson Norde as standard equipment on both the 6x4 and the 8x4.
The cab is the GT high roof version of the Club-of-Four design also used on the Manager range. The cab floor has been raised 60mrn over the old model to accommodate the larger radiator (and charge-cooler) demanded by the power rises. This is necessary to ensure adequate cooling.
Ground clearance was also increased by 90mm on the new Maxters. A sump/radiator guard is part of the standard specification.
Other changes include three-step cab entry (the first retractable), roof-level air intake, a vertical exhaust and headlight guards.
Two six-wheelers were introduced in the UK, the other a 338hp (252kW) high power, or TI model using an charge-cooled version of the eight-wheeler's motor. Few of these have been sold here.
The tipper chassis uses a 6min flitch referred to by Renault as its level B strengthening. This readies the chassis for on/off road work, the sort typified by any UK aggregate operation. There is also a level A non-flitched chassis for non-tipping, on-road only applications. An an 8mm C-rated flitching is available for more severe and off-road work such as in quarries.
Rear suspension is Hendrickson Norde rubber on a 19-tonne bogie; front springing is parabolic steel with an anti-roll bar. The rubber system is largely maintenance-free and would be ideal for on-road work which doesn't demand high articulation of the drive axles. Two-spring rear steel suspension is available as an option.
Power comes from the Renault MDR 06.20.45D3 Euro-1 engine. Its 9.8-litre capacity develops 298hp (222kW) at 2,100rpm and 8741bft (1,185Nm) of torque at 1,300rpm. Electric cold start aids are fitted, as is an allspeed governor for PT-0 work.
The nine-speed B9 gearbox offers a range of PT-0 outlets with power ratings up to 7231bft (980Nm). The clutch is power-assisted twin-plate asbestos lined. Power passes through the synchromesh box to the 5.125:1 final drive bogie incorporating 2:1 hub reduction axles. Airoperated cross-axle diff locks are standard. There is no inter-axle differential.
With its 0.75:1 overdrive top gearbox ratio the truck has an overall geared speed of 31mph at 1,000rpm on its standard Michelin 11 R22.5 XZB on/off road tyres. The front tyres are on/off road Michelin 315/80 R225 XZYs, plating the front axle to 7.5 tonnes.
ZF power provides exceptionally light steering, making what is a rock stable chassis exceptionally manoeuvrable. However the rigidity inherent in the rubber rear suspension can make the truck feel rather tail heavy. OTS has complained of understeer in the past: given the light steering this description is understandable.
From our experience, the problem, if it can be described as such, is more a lack of balance within the chassis. The driver will always correct for such variances, but OTS has questioned the lack of a third differential between the drive axles. Renault says the design is well accepted, offering the advantages of simplicity and light weight.
The G300.26D failed, as did the G340ti.32D eight-wheeler tested last year (CM 2-8 September 1993) to deliver the promised 18metre swept turning circle. But Renault is not alone in its guilt on this one. • PRODUCTIVITY
Well run in with more than 90,000km on the clock, the Maxter gave a good measure of its potential for fuel economy. Compared to previous 6x4s tested (at 24 tonnes) the Maxter showed exceptional productivity, as did its 8x4 big brother tested at 32 tonnes.
As with the eight-wheeler some of the other trucks in the comparison tables (page 49) showed better figures, but all ran at the lower weights.
Deep gearing kept the engine spinning fast on the motorway and helped sustain performance on the A-road and hilly sections. We ran the motorway sections of this test at the new 56mph (90km/h) speed limit to help future comparisons.
With this truck, however, because of the speed and weight changes, comparisons are hard to make. But study of the figures reveals some noteworthy facts.
Robbed of the 1,610kg payload increase, the comparable 24-tonne body/payload allowance is only 16.8 tonnes, ie: the worst of the bunch by a clear half a tonne. The 8x4 Maxter told the same weighty story. Renault must get some metal out of the Maxters if they are ever to compete in Britain.
The truck was the quickest of the bunch overall, and on the A-road section. But not surprisingly, considering the extra payload, its fuel consumption fell down on all but the motorway stage.
ill • ON THE ROAD
By modern standards acceleration was reasonable for a truck of this power—compared with typical six-wheelers of just a few years ago, this truck is a positive flyer. The rise to 26 tonnes has done little to dampen the effects of all that extra power.
The eight-wheeler's brakes v.,,ere sure footed and instant. Not so the six-wheeler which, according to OTS, has undergone a surfeit of brake work under warranty
Our track tests at MIRA recorded good enough stopping distances once sufficient pedal pressure was applied, but it did take some force to get it there.
All in all the brakes felt adequate, but not great, for this class of vehicle.
The Renault's rigid rear suspension coupled with the light steering makes the truck's handling predictably cautious. The ride is solid in a straight line and through the bends There's almost no roll from the chassis or the cab. We found we preferred to spin the chassis through the Cotswold hills with the palm of one hand. Manoeuvres were performed in the same lazy way.
The MIDR engine comes with an effective exhaust brake, effective just so long as you keep your road speed down and engine speed up, that is.
The deep tipper gearing helps, but there's no substitute for caution. Every descent could be tackled without the aid of the service brakes, as long as you went slowly.
On the road performance is generally good. The lugging ability of this engine tended to make us lazy We skipped the occasional downshift, but the engine's forgiving nature gave a full recovery Road speed fell away but was soon regained.
• CAB COMFORT
The Maxter cab is deceptively high. Getting aboard is quite a job but the well designed grab rails are useful given the need to jump in and out of this type of vehicle frequently.
The familiar Club-of-Four cab has been given an all-new interior including a new twospoke steering wheel and a foot-operated steering adjustment. The column's wider movement should suit most needs. The extra headroom in the GT cab is certainly an improvement.
The high roof offers overhead bin storage and there's a rear bulkhead bin, but no door pockets. Bottle jack, wheel brace and cab tilt bar reside behind the two seats. The flat wide engine cover could be used as an oddments tray, or at least something to retain things placed on it.
Soft sound absorbing material covers the walls and ceiling. Padded rubber covers the floor helping to keep in-cab noise down, The sound meter again confirmed the impression we gained at this truck's launch, and during our tanker test last year.
The new dash is well lit and competently laid out. It's also easier to clean. The same number of instruments as before have been rearranged into a more logical layout, bringing the more important ones into clearer view.
Taken together all these changes revitalise an old cab. Taller drivers still have to twist a little in the seat to see under the roofline, but at least there's greater vertical travel in the new seats.
• SUMMARY
This truck is too heavy. That's its greatest failing. Like its 8x4 big brother it weighs more than any competitor in its class, which is a shame because it performs so well in other areas. This shortcoming is particularly baffling as Renault's UK engineering centre had such a hand in the truck's design. To compete on equal terms with lightweights from ERF and others it needs to go on a diet.
The truck's contract maintenance and spare parts prices are no more than average. Renault has a historical problem in the UK with the strength of its dealer network, not least on spare parts availability. The company's biggest problem continues to be a lack of faith among potential buyers.
Nonetheless, Renault's best salesmen are its products. They have consistently recorded some of the best fuel economy, journey times and productivity figures in CM's truck test history If hauliers can be persuaded to try them once, we reckon there's a good chance that some long-held views could be changed. E by Danny Coughlan
Our thanks go to Bruce Woodall. Bernie and their team at OTS for the opportunity to drive this truck.