13 March 1999

TRY

A SUPER SINGLE FOR SIZE

Staying single was the best option for a Suffolk business which wanted the benefits of flotation and good grip combined with safe road use.

EQUIPPING tractors with sufficient tyre rubber to give adequate traction and low ground pressure for autumn operations is invariably a compromise.

Single wide section tyres will give enough grip but insufficient flotation for seedbed work; dual wheels usually give enough of both but are unwieldy; and true flotation tyres rarely offer sufficient grip, load capacity or bead integrity to cope with heavy draft work on big tractors.

However, Suffolk farmer Gerald Western believes he has found a tyre that comes closest to combining the best of these characteristics in Michelins latest ultra wide, low-profile radial. At up to 1.05m wide, the XM609 (and its newly introduced successor, the MEGAXBIB) is designed as a super single tyre for tractors and harvest machinery.

"Weve used duals, and they are very effective," he says. "But with land spread some distance apart they are a real nuisance when you want to move from field to field. The big XM609s we run on our 190hp tractor give us lots of flotation and no inconvenience."

Growing 625ha (1,544 acres) of arable crops (plus set-aside) at The Grove, Brundish, near Woodbridge, and on a neighbouring farm on contract, Mr Western focuses almost exclusively on seed crops. So a high level of management attention to detail is essential at all stages of production to ensure both quality and yield.

The cultivations approach mainly involves ploughing, followed by heavy rolls, with seedbeds then worked down and sown with a power harrow or coil and tine combination cultivator coupled to a pneumatic seeding outfit.

Timeliness of operations, and avoiding the soil compaction that can restrict early seedling and subsequent root growth, are key requirements to hit target drilling dates and encourage strong establishment.

"With drilling capacity already under some pressure, wasting time removing and fitting dual wheels every time we need to move the tractor some distance is something we can do without," says Gerald Western. "At 4m wide, it is just not practical to run down narrow lanes with the extra wheels fitted. Besides, there is a risk of breaking tractor half-shafts if you have to run the outer wheels up a kerb or grass verge to give oncoming traffic room to pass."

More manageable

Despite a section width of 1.05m (3ft 5in), the XM609s – supplied on specially-made rims by Warwickshire-based Sam Moreton & Sons – limit overall width of Mr Westerns 190hp Fendt Favorit 818 to around 3.2m (10ft 6in), creating an outfit that is more manageable in the field as well as on the road.

Sidewall flexibility is one of the key aspects of the XM609 design; it allows the tyre to deform naturally to present the biggest possible footprint for minimum impact on soil structure and maximum traction.

At the same time, the tyres large volume and tough carcass structure allows it to carry big loads at modest inflation pressures. At 2.4 bar (35psi), the largest size in the range is rated to carry 8,290kg at up to 30kph, and more than 1,050kg where speed is restricted to 10kph. That makes it suitable for use on harvest machinery as well as tractors operating heavy mounted implements.

With a folding tyre press and seed hopper carried up front, and a heavy 6m power harrow and seeding coulters on the back, Gerald Westerns Fendt 818 has an all-up weight of around 13 tonnes. Yet the Michelin rear drive tyres can be run at just 0.69 bar (10psi) in the field, notes driver Paul Wilby.

"Sidewall deflection looks a bit much at times but that is what the tyre is designed to do," he points out. "It spreads the tread lengthways and sideways to make a big contact area."

With a handy built-in air supply on the Fendt, the tyres can be pumped up to 1.1 bar (16psi) or more to cope with longer road journeys, stiffening the sidewalls to improve stability when travelling on main roads at speed.

Paul Wilby concedes that, with relatively shallow, close-spaced lugs, traction can be a bit wanting when ground is wet and sticky, especially as the front press tends to take some weight off the front wheels.

"But it is not a major problem and its small price to pay for the convenience when it comes to move to another field," he says. "With duals, it can take an hour to move and you need someone to bring the outer wheels separately; with the XM609s fitted, I just fold up the press and cultivator and Im away without even leaving the tractor seat."

With an outfit capable of preparing and seeding ground at up to 30ha (75 acres) a day, the ability to move without downtime improves the seasonal workload potential of the outfit. In a catchy season, that can make the difference between hitting and missing key variety drilling dates.

Gerald Western sums up: "I had some reservations about changing from duals but experience so far suggests we made the right decision. On two occasions weve drilled peas in the spring alongside a rubber-tracked tractor and the prints left were very similar; that proves the flotation capacity of the tyres.


Load capacity Max load Equivalent

at up to 30kph at up to 10kph 80-series*

1000/50R25 6,740kg @ 9,450kg @ 18.4R30

2.4 bar (34psi) 2.7 bar (39psi) 16.9R34

14.9R38

1050/50R32 8,290kg @ 11,630kg @ 20.8R38

2.4 bar (34psi) 2.7 bar (39psi)

* with similar overall rolling radius.