Rather than putting all the set-up and selection focus on the front tyres of a combine, as traditionally happens, it is now suggested more attention should be paid to the rear tyres.
While much of the attention is on the front axle when it comes to specifying combine tyres, farmers are now being advised to give greater consideration to the rear tyres.
As machines get larger, the lack of adequate rubber at the rear can have severe adverse effects when it comes to soil compaction and load-bearing capability.
Gordon Brookes, customer engineering support manager at Michelin, believes the issue is increasing in importance as harvesters grow in size, weight and power.
He also warns most machinery dealers do not focus heavily on tyres when securing an order, so farmers should seek expert advice from their tyre manufacturer or dealer.
Offering advice ahead of the 2019 harvest season, he says: “The rear axle is the smallest tyre, so that is always going to be where the damage is most likely to be done.
“Farmers naturally look at the front because that is where everything is going on, while often forgetting the back end is extremely heavy when completely full – despite being on a small tyre.”
A MAJOR area where Mr Brookes says farmers should focus their attention is tyre pressures.
He says: “Nearly all machinery manufacturers leave tyres at the fitting pressure – normally about 35psi – and then the dealer is supposed to amend the pressure if it is appropriate prior to delivery. But only a small percentage do; invariably as they do not know how the machine will be used.
“If the farmer is combining linseed, for example, it has a different density to wheat or barley – and the tyre pressures are dependent on what you are harvesting.”
All tyre manufacturers should be able to provide bespoke tyre pressure recommendations. Mr Brookes says setting up new harvester tyres correctly is essential, particularly if you have gone for a high technology fitment.
“Also, bear in mind that a typical combine might have a couple of different headers and they will all be different weights,” he says.
“The tyre pressures will be different in each scenario.”
MR Brookes says: “When travelling without the header mounted, there is no weight transfer from the rear axle, so the rear tyre loads can be high.
“Sometimes you will even see the rear axle specified on the same tyres you would fit on a loader, so shifting some of the focus from front to rear would pay huge dividends as far as soil compaction is concerned.”
While four-wheel drive harvesters require lugged tyres on the rear, farmers can access a wider range of fitments if they are specifying a two-wheel drive machine, Mr Brookes says.
“If minimising compaction is your number one issue, then you can select a flotation tyre, such as the Michelin CargoXBib,” he says.
“This is designed to spread the weight of laden agricultural trailers.”
MR Brookes’ final tip is to opt for the latest cyclic field operations (CFO) rated tyres where possible, because they offer the highest load capacity and the lowest pressure for a given load.
A CFO tyre has the ability to flex and adapt to the constant changing load put on it by the combine.
Mr Brookes adds; “Our CFO-plus rated tyres are based on a 1,500-metre cycle.
“There are other cyclic markings for other tyres on the market, but the load benefit is not as high, and the cycle distance not as great. Some are only up to 600m, plus they can come with other limitations for things like working on side slopes.
“It pays to specify the best tyre you can from the outset.”