2014-03-12   facebook twitter rss

Tyre Choice and Pressures Critical Following Extreme Weather

Unprecedented wet weather across all regions of the UK this winter could cause lasting damage to soils and soil structures that may take years to put right. But, through careful choice of tyres and optimum setting of pressures, the effects can be minimised, according to Mitas Tyres Limited, the UK’s leading off-road tyre manufacturer.

Record rainfall over the last few months has created potential long-term issues with the soils on most farms, so careful management will be the watchword going into the spring, advises Ron Wood, a Technical Consultant who works with Mitas Tyres. The correct choice and operation of tyres will, he emphasises, be even more important than normal in minimising the damage caused by agricultural machinery, as well as obtaining optimum machine performance under unusually difficult conditions.

Ground contact patches made by the same tyre, carry an identical load but at different inflation pressures. The tyre on the left is inflated to 0.6 bar, the tyre on the right to 1.6 bar

Ground contact patches made by the same tyre, carry an identical load but at different inflation pressures. The tyre on the left is inflated to 0.6 bar, the tyre on the right to 1.6 bar

With many fields at or close to their maximum water-holding capacity and many having lost a considerable amount of their structure, it is vital that operators recognise the importance of correct tyre choice and settings under these conditions. Spending time focusing on these areas will deliver significant benefits.

“There is generally a conflict between what is required of tyres and the demands placed on them in the field and on the road, particularly in the case of tractors which operate at higher speeds,” Mr Wood explains. “Field work typically requires low inflation pressures, whereas higher pressures are required for road work. The best way to reduce the pressure differential between field and road use, and thereby the need to adjust pressures, is to fit the largest tyre possible.”

Where there is no limitation on tyre width most farmers will opt for a wider tyre to maximise traction, such as the Continental SVT (Super Volume Tyre) which will also allow an approximate 20% reduction in inflation pressure to carry the same load compared with a standard tyre when working in the field. For specialist applications which require a narrower-section tyre to be fitted, such as row-crop working, a considerably higher inflation pressure is required. There has been a trend to mitigate this by fitting wider row crop tyres up to 380 mm or even 480 mm in width from the more typical 300-320 mm, the increased air volume allowing a useful reduction in inflation pressure.

The relationship between ground pressure and tyre inflation pressure is approximately one-to-one, so the aim should be to select a tyre which will operate at the lowest possible pressure for a given load and speed. This will maximise the area in contact with the ground and help to keep the machine on top of the soil, avoiding ruts which will cause operational issues and have to be removed at a later stage. Setting tyre pressures correctly will also minimise wheel slip, reduce fuel consumption by up to 20%, increase work rates, result in less wear-and-tear on machinery, improve operator comfort and significantly reduce maintenance costs.

At higher speeds on the road, higher pressures will be required and adjusting them to the correct levels recommended by the manufacturer will improve steering accuracy, braking performance and stability, contributing to much safer operation and avoiding overheating of the tyre. Correctly-adjusted tyres will also reduce rolling resistance and fuel consumption, wear more evenly and last longer.

Mr Wood suggests that in difficult field conditions operators should consider reducing the loading on the tractor to allow lower tyre pressures to be used, whilst remaining within manufacturer’s guidelines. In the case of a draft implement such as a plough that could mean dropping a furrow or only partially filling linkage-mounted or trailed equipment such as a sprayer or fertiliser spreader.

Establishing the correct pressure for a particular application may take a little time and effort initially, says Mr Wood, but will pay for itself time and again through improved machine performance, reduced soil damage and lower operating costs.


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