Spending a few minutes checking combine tyres after harvest and preparing them correctly prior to the machine being stored away for winter could save farmers thousands of pounds in unnecessary replacement costs next year, according to Mitas Tyres.
“Replacing combine tyres is very expensive and often caused by poor maintenance, so it makes sense to look after them correctly,” emphasises Mitas Tyres UK automotive engineering manager Ron Wood. “A key part of the process is to ensure that tyres are stored correctly between harvests, because this will maximise their life, avoid costly failures and minimise unplanned downtime at a critical time of the year.
“The short, very intense period for which combines are used each season and busy autumn drilling period which follows means that these machines are often forgotten once harvest has been completed. However, it is very important to ensure that combines are thoroughly cleaned and correctly prepared for long-term storage.
“During the nine or ten months when the machine is not being used it should ideally be supported on blocks to take the load off the tyres, which should have their inflation pressure reduced to 0.7 Bar. If it is not possible to store the combine in this way then inflating them to their normal operating pressure will prevent ‘flat spots’ from developing when the machine remains static for a long period.
“Pressures should also be checked periodically and, if possible, the combine moved slightly to rotate the tyres, so that the weight rests on a different part of the circumference. Tyres should also be protected from direct sunlight by storing the machine in a closed, dark barn, but if that is not possible then each one should be fitted with an opaque cover to prevent light from degrading the rubber.”
“Taking a few simple steps to look after a combine’s tyres will pay dividends, not only in terms of keeping the machine operating reliably, efficiently, safely and at peak productivity during next year’s harvest, but also avoiding unnecessary downtime and replacement costs.
“Combine tyres do not tend to ‘wear out’ in the conventional sense and can have a very long service life. Most still have plenty of tread remaining even when they actually need replacing, so potential problems often go unnoticed. However, any shortfalls in the tyres’ integrity will be quickly exposed when the machine is used again due to flexing of the sidewalls, so it is important to check them carefully for signs of excess wear, damage and incorrect operation.
“Punctures and accidental damage are the most common reasons for replacement, but older combine tyres often have to be withdrawn from service because of ageing cracks, which are caused by ozone in the atmosphere attacking the rubber compound and causing it to degrade. This is particularly the case on farms in coastal areas, where the ozone concentration in the air is much greater. Tyres should also be stored away from high-capacity electrical equipment, such as a welder, as this will also increase the level of ozone in the air and cause tyres to degrade more quickly.
“Although ageing cracks, particularly those in the sidewall, may appear quite narrow and shallow they can quickly become wide and deep with flexing in service, leading to gradual pressure loss or even sudden failure. In this case the tyres should be replaced as soon as possible with ones that match or exceed the manufacturer’s original specification.
“Demand is increasing for wider drive axle tyres which can operate at a lower inflation pressure, thereby reducing the ground pressure. Mitas offers a range of larger sizes, 900/60 R 32, 900/70 R 32 and 1050/60 R 32, which provide higher load carrying capability at lower pressures, while the new Mitas 800/70 R 32 SVT CHO (Cyclic Harvesting Operation) 175A8 (172B) tyre has been designed to maintain the overall width of the combine within 3.5m. It allows a lower inflation pressure for a given load when used in cyclic operation at 10kph, which means that the sidewall deflection is increased, resulting in a longer contact patch and lower ground contact pressure. Whereas a standard tyre at a load of 10,710 kg requires an inflation pressure of 3.0-bar, the CHO tyre requires only 1.6-bar.
“With more time generally available for machinery maintenance during the winter months it is good practice to fit replacements then to avoid the pre-harvest peak in demand which occurs every year, when delivery times increase,” recommends Ron.