What is the right load distribution for my tractor tyres?

Ensuring an even distribution of weight across your tractor tyres is essential if you want to work efficiently.

Tractor with excessive loadEnsuring an even distribution of weight across your tractor tyres is essential if you want to work efficiently:
1. Your traction capacity,
2. The preservation of your land
and the growth of your crops
3. How quickly your tractor tyres will wear down
4. The overall balance of your vehicle
and therefore your safety and that of your equipment. Subjected an axle to too heavy a load could have serious consequences...

 

What are the consequences of placing excessive loads on my tractor tyres?

Excessive load on tractor tyresYour agricultural tyres are the only things connecting your tractor to the ground. If you overload your trailer or hitch mounted or semi-mounted tools that are too heavy, the weight of the tractor will crush the tyres.

If the soil is hard, the tyre's lugs will bend under the tractive force, until they tear. The deformation due to compression will be lateral and affect the sidewalls, which are not designed to be subjected to so much force. This increases the risk of internal casing rupture.

There are many potential consequences, the least serious of which in the short term is soil compaction, which will gradually reduce your productivity. Extra cost will be the first visible consequence of overloading, as your tyres will wear down much quicker.

Driving on roads will definitely be more of a problem, because if you need to use the emergency brake and you're overloaded, your tyres might not be able to respond as expected and you could be put at significant risk.

 

Defining the maximum load index

It's often hard to determine the maximum weight your tractor tyres can endure with accuracy, so how can you be sure that you're not exceeding the maximum load that your tyres can handle? What weight should you put in the front to offset the weight of the tool behind, without exceeding the load limit for your tyres? These are answers you need to know if you want to avoid having to replace your tyres once a year.

Agricultural tyre load indexThe maximum load index is indicated on your tractor tyres, as a number usually between 75 and 190 along with a speed code that could either be a letter or a letter and a number (such as A1, A2, A8, B, C or G) that corresponds to a precise speed.

The tyre manufacturer should have provided you with an equivalence table so that you can see the exact weight for this index for any given speed. This weight is the maximum load per tyre that should never be exceeded.

 

Why do I have to increase the size of my tyres to increase the load capacity?

The tyre mount originally supplied with your tractor is rarely the most efficient – it's usually just whatever's cheapest for the manufacturer.

So if your tools are heavy and you need to work in all weathers on soft or heavy terrain, the best choice would be to increase the diameter of your rear wheel to its maximum possible size. This will allow you to carry heavier loads because the volume of air contained in a tyre is proportional to the weight it can bear.

The bigger the tyre, the higher the air volume
and the heavier the load it can carry.

 

Managing the load transfer to my tractor tyres

The total weight of the tractor and its mounted or semi-mounted tools exerts a force that presses down on your tyres. This force is then transferred to the ground and compacts the soil to a varying degree, depending on the inflation pressure of your tyres:

  • If the load being transferred is heavy, you need to rebalance your tyres by increasing the pressure otherwise they will be compressed too much.
  • However, do remember that, if the pressure is too high, there will be excessive soil compaction and ruts are more likely to form.

 

Balancing load distribution

LWeight is distributed based on your tyres' properties. If your tyres are all the same size, they will each be subjected to the same load.

For 2WD tractors, at least 20% of the tractor's total weight must be placed on the front tyres. This balance is necessary to guarantee the effectiveness of the steering shaft.

With an unequal 4WD tractor, the weight must be distributed 40% at the front and 60% at the rear. If a semi-mounted tool generates substantial load transfer on the rear wheels, you will need to rebalance the vehicle with extra weight on the front.

 


To learn more and boost your farm's profits, Bridgestone-agriculture is offering you a free, detailed eBook that explains the essential role your agricultural tyres play in your productivity.

Download eBook: Increase the profitability of your operation

The information contained in this publication is for guidance purpose only. Whilst every effort has been taken in its production, no responsibility can be accepted for any loss or damage arising from any kind of undetected technical or commercial error contained in this content. Any data supplied in this publication is subject to possible revision following the date of publication. Due to the constant advance of tyre technology, the contents of this publication are subject to change without notice.