Michelin CerexBib Designed for Heavy Loads from Modern Harvesters

Farmers today are harvesting crops during the short peak maturity period in an effort to increase yield per hectare, and harvester productivity plays a key role in this. This is increasingly common practice as farms increase in size and farmers come under pressure to carry on in less than optimal weather conditions. During wheat harvests, today’s machinery covers six hectares an hour, compared with just one in 1965.

This ramp-up in production has seen the introduction of more powerful, heavier and wider harvesters, yet manufacturers of these machines have to take factors such as soil compaction, load capacity and traffic regulations into account when designing something ‘bigger and better’. Michelin has been tackling these issues together with combine harvester manufacturer Claas and has developed tyres for the latest generation of farm machinery – a range of harvesters with wider, 12 metre headers, 11 ton conveyers (compared with six tons in 2003), hybrid systems and larger axial combines for higher efficiency per hectare, more powerful beaters, automatic levelling sieves and engines putting out more than 600hp. Entering Michelin’s agricultural portfolio in the second half of 2010 is a tyre taking these growth developments into account –CerexBib, the third tyre to utilise Michelin’s Ultraflex technology.

This technology centres upon a tyre’s architecture and ways of using it to the farmer’s advantage. Michelin states that conventional agricultural tyres are governed by a basic rule that determines the recommended pressure according to load and speed; if a load or speed increases, the pressure increases. With Ultraflex, however, Michelin says this rule has been overturned: the manufacturer says its patented technology makes it possible to optimise pressure regardless of vehicle speed. When vehicle load or speed is increased, tyre pressure is always less than that used for the same-size tyres employing traditional construction. Through this, soil compaction is reduced, protecting fields and maintaining their full yield potential.
 
Soil protection is not the only benefit provided by Ultraflex technology. The larger contact patch and lower ground pressure also reduce rut depth and increase traction on wet and dry soil, saving time and increasing fuel efficiency. These performance improvements are aligned with recent farming practices, such as direct seeding. According to Michelin, important Ultraflex features built into the CerexBib include a flat crown in order to lower soil compaction and increase tread life, a low-hysteresis rubber compound that limits heat generation in order to increase working life, reinforced shoulders to ensure endurance despite high deflection, thereby enhancing the casing’s resistance to severe mechanical stress due to load or speed, more flexible sidewalls to increase ride comfort and a wider rim to improve road handling at lower pressure.

Thanks to Ultraflex technology, Michelin says the new CerexBib is the only commercially available tyre that can work at a pressure of less than 2 bar. Furthermore, Michelin says a higher rate of deflection and a 30 per cent lower working pressure gives the CerexBib has a 20 per cent larger footprint than a conventional tyre, and thus soil compaction is minimised. A further reported benefit the tyre’s architecture offers is a longer footprint; Michelin says this widens the harvest window, because the CerexBib can take wet weather in its stride. Steeper slopes can also be tackled – Michelin reports that a combination of Ultraflex technology, the compounds used and the tread pattern employed enable the CerexBib to climb slopes of 24 per cent as opposed to the 19 per cent that conventional tyres can handle.

New harvesting machinery is much heavier than equipment previously used and to counter this Michelin says the CerexBib can, in comparison with a conventional harvester tyre, carry an additional 20 per cent load capacity for the same tyre pressure. When used on-road – an increasingly unavoidable aspect of harvester usage – the CerexBib offers the advantage of being some 15 per cent narrower than  currently available tyres; for example, the Michelin CerexBib IF 680/85 R 32 has the same load capacity as the current 800/70 R 32. This lets manufacturers build larger harvesters without exceeding a width of 3.5 metres, the maximum width permitted under European Union regulations without the presence of an escort vehicle. Also pertinent to on-road use is a tyre’s effect on vehicle handling, and Michelin reports that despite the use of lower pressure, its Ultraflex engineered tyres deliver stability with improved steering response and reduced vibrations.

Michelin states that the CerexBib is the first tyre that can be used on both a combine harvester’s front and back axles, with operation at even less than 2 bar possible on the rear axle fitment.