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Ballast in Tractor Tyres

 

One of the commonest arguments that we at OKO hear from famers about why they ‘cannot’ use tyre sealant in their tractors is that they must ballast their tyres (usually just their rear tyres) with water for reasons of traction

This is actually not good practice – and if you don’t believe our (admittedly biased) view, here is a report from The Land agricultural newspaper in Australia, about a major tractor manufacturer’s proof that water ballast is bad news.

What’s the worst way to ballast a tractor? By putting water in the tyres, farmers at a recent Case VIP Field Days in Tamworth were told.

The seminar on ballasting, run by Case’s tractor product manager, Phil Withell, was a revelation to those farmers (and they are many) who hold to the traditional wisdom that the first thing you do on buying a tractor is to fill its tyres with water. But Mr Withell told farmers at the seminar that this was a sure way to sap engine power and increase fuel consumption, because as the water continually tried to return to its level it exerted internal friction counter to the tyre’s rotation.

 

And because a tractor should carry “just enough” weight for the job, and ballasting requirements vary between applications, water-ballasted tractors are often too heavy for much of the working year. Side-effects of incorrect ballasting can include increased soil compaction and greater wear and tear on the machine.

 

In a startling demonstration, Mr Withell showed a Case experiment in which identical tractors were loaded with 320 kilogram of weight over the rear axle – one in the form of water ballast, another with cast weights. The two tractors were then run under identical conditions for 45 seconds, at the end of which the tractor carrying the cast weights was nearly a tractor length in front of the other. “The loading on the water-ballasted tractor amounted to only 80 litres in each dual tyre,” Mr Withell said. “Most tractor tyres have a capacity of about 450 litres, and there are farmers who take the same attitude to putting water in tyres as they do with putting fuel into the tank: they fill ’em up.”

 

There were other advantages to using cast weights, not the least being that “suitcase” type weights were easy to take on and off. This was important, Mr Withell said, because optimal ballasting was different depending on the application. Suitcase weights were also advantageous in that they exerted leverage over an axle. Suitcase weights fitted to the front increased load to the front axle, and reduced weight to the rear, and visa versa; but the overall weight remained unchanged. Mr Withell advised six steps towards achieving the correct relationship between the tractor and the ground:

  1. Use the Case table to determine the total operating weight for your tractor.
  2. Use cast-wheel andor suitcase weights to adjust the weight.
  3. Establish correct weight distribution according to the implement and tractor type.
  4. Using tyre manufacturer load and inflation tables, set the tyres to the correct minimum pressure. It is vitally important to set tyre pressures according to the weight they carry.
  5. Under normal operating conditions, measure wheel slip. This should be in line with the Case chart. If wheel slip is outside the guidelines, re-trace steps the first four steps listed here.
  6. Correct any power-hop. On MFD tractors, add two pounds per square inch to the front tyres and test again. If power-hop continues, add another two psi. Continue to add two psi, checking performance until the hop is eliminated. But never exceed the tyre maker’s recommended maximum pressures. On four equal-wheel-drive tractors, add two psi to the rear tyres until the problem is eliminated. With duals or triples, all tyres on an axle should be set to the same minimum pressure.”

So taking this into account, the use of cast weights as needed, plus a few litres of OKO in your tyres, will give you the multiple benefits of improved traction, reduced fuel consumption and cost, reduced damage to your land, and of course fewer punctures and tyre replacements – which given the cost of tyres and the downtime if you do have a flat, means a considerable improvement to your bottom line.

Remember that OKO Off Road lasts the life of your agricultural tyre, sealing multiple punctures again and again, so the modest investment in the tyre sealant has a great payback.

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