| BUYERS GUIDE
WIDE WHEEL AND SUSPENSION CHANGES FOR MOTORHOMES
Dual rear tyres and heavy truck springs aren't always ideal
You don’t have to buy an Earthcruiser motorhome to take advantage of this company’s ADR-approved wide-single, forged aluminium wheel and suspension upgrade package.
The original Earthcruiser 4WD motorhome was built on Japanese light truck chassis, because that was the only option in the marketplace. Now, most Earthcruisers are built on Iveco Daily 4WD chassis that offers better ride quality and easier access.
However, many Earthcruiser buyers request Fuso Canter or Isuzu NPS cab/chassis and nearly all of them opt for the wide-single-wheel package, to replace Japanese-standard skinny singles up front and duals rear. Also, the Iveco Daily comes on single tyres, but they'e not wide enough for many buyers.
Canters and NPS light trucks are designed primarily as load carrying gravel-road and hard-surface, off-road vehicles. Dual rear tyres obviously allow greater payload than singles.
However, for typical Australian off-roading conditions that include beach and desert sand, and mountain trail mud, skinny front tyres dig in very quickly.
Duals aren’t ideal in these conditions, either, having too much flotation at light loads and insufficient grip. Duals also capture large rocks that can damage sidewalls and fly out with damaging potential at road speeds. They also can’t be deflated without risk of the sidewalls clashing.
Another problem with single-front and dual-rear wheels is that the rear tyres can’t follow in the front tyre tracks, making off-road driving more difficult and ‘staking’ on tree roots more likely.
Standard Japanese light trucks have a ride commensurate with their payload capacities: firm at light loads and more comfortable at GVM. For recreational use a softer-riding suspension is desirable.
Early in its development on the Fuso Canter cab/chassis the Earthcruiser was fitted with longer-leaf springs, much greater capacity shock absorbers and equal-track wide-single wheels and tyres at both ends. With correct tyre selection GVM wasn’t affected.
These design characteristics continue on today’s Earthcruisers and the company has made its suspension and wheel technology available to people who don’t necessarily want an Earthcruiser motorhome: some want to make their own bodywork, or use a slide-on camper and others want a big working ute that handles off-road conditions more easily, with a better ride.
The Earthcruiser arsenal includes purpose-designed, forged-aluminium 11-inch-wide x 17-inch-diameter single wheels. These wheels are available in three different models, for the Iveco Daily 4x4; the Fuso Canter 4x4 and the Isuzu NPS300 4x4.
Forged aluminium wheels are much stronger and more crack-resistant than cast wheels. Heavy-truck aluminium wheels are almost universally forged types, whereas nearly all 4WD aluminium wheels are cast. (At OTA we won’t take cast aluminium wheels on serious bush expeditions.)
The one Earthcruiser wheel type fits front and rear positions on the two Japanese trucks: it’s simply turned around to create positive offset at the front and negative offset at the rear. Both faces of the wheel nave have radiused holes, for optimum wheel-nut seating.
It’s obvious that at the rear the single rear wheel centre line is slightly outboard of the dual-wheel centre line, but the Canter and NPS300 have massive rear axles, with large bearing assemblies that are unlikely to be stressed by this altered load path. (The Isuzu’s rear axle alone can carry the truck’s rated GVM!)
Earthcruiser’s preferred tyre for these wheels is Toyo’s Open Country 37x13.5 17-inch, 10-ply, mud-terrain radial. It has a load capacity up to nearly two tonnes at 80spi – 3.9 tonnes per axle – so the truck manufacturer’s GVM isn’t affected.
The suspension changes start with moving the spring hangers of the front and rear axles rearward by 100mm and fitting more-cambered, longer taper-leaf springs front and rear. A suspension ‘lift’ around 50mm is part of the exercise. The new spring rates are softer and matched to larger-bore shock absorbers.
The finishing touches are changes to the front step, a fibreglass infill panel between the front wheel arch and the tyre, and a wider front mudguard. There’s also a moulded open-top centre console that can replace the centre (third) crew seat in Fuso and Isuzu cabs.
Earthcruiser can modify a brand new truck, before registration and affix a secondary manufacturer’s compliance plate to it.
In the case of a registered vehicle the company can fit the wheel, tyre and suspension kits at its Helensburgh, NSW factory, but engineering certification for States other than NSW needs to be organised by the truck owner.
The conversion isn’t a cheap exercise, because each forged wheel with tyre is around $1700. The suspension change includes relocating a rear cross member and costs around $6000, with the infill panels and wider front mudguards.
OTA checked out a brand new Fuso Canter 4x4 that had been given the Earthcruiser treatment, including a steel bull-bar, winch and suspended passenger seat.
Being an unladen cab/chassis this truck still had a very firm ride, but we know from testing previous Earthcruiser Canters that the ride evens out markedly when a load goes on the back. The owner, a tradie, intends to build a custom motorhome on the back of it.
For further info check out Earthcruiser at: http://earthcruiser.net.au/
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