Upsize your tractor
tyres for 35% more load

So you've decided to increase the size of your tractor wheels to improve its performance, and in particular its loading capacity, which can increase by 35% with the right tyres.
But watch out – there are some pitfalls to avoid that could cost you dearly.

Increasing the size of tractor tires = more performance

So you've decided to increase the size of your tractor wheels to improve its performance, and in particular its loading capacity, which can increase by 35% with the right tyres. But watch out – there are some pitfalls to avoid that could cost you dearly.

As you are no doubt aware, increasing the size of your tractor's wheels and tyres will improve its performance: soil compaction will be reduced because there will be a larger surface area in contact with the ground, and there will be less slip for the same reason. As a result, your tractor will use less fuel and, most importantly, it will be able to pull heavier loads because the volume of air inside a tyre is proportion to the weight it can bear. In short, bigger tyres mean bigger loads.

The tyre mount originally supplied with your tractor is rarely the most efficient. So if you use heavy tools and have to work in all weathers on loose or rough terrain, the decision to get the largest diameter rear wheel possible is a no-brainer.

Remember, if you want to increase the wheel to its maximum diameter, you should also minimise the rim diameter to make sure you're increasing the volume of air. This is why the tyre you choose is crucial.

Tractor tyre, load capacities

Two identical tyres will have very different loading capacities depending on their quality. A low-cost or budget tractor tyre may be appealing from a financial point of view, but it won't be in the same class as a tyre labelled as IF or VF technology, which is made from materials that can withstand considerable deformation of the sidewalls and is therefore capable of bearing 35% heavier loads.

When it comes to tyre width, it's the type of work you need it for that will be the deciding factor. For ploughing, if you increase the width you'll have better contact with the ground, and therefore optimal tractive force.

For treatment on the other hand, if the tractor needs to pass in between crop rows it will need much narrower wheels.

 

Pay attention to preponderance in 4WD tractor tyres

Respect the preponderance of 4WD

Respect the preponderance of 4WD

Once you've determined the maximum rear wheel diameter for your tractor and chosen the right agricultural tyre, you'll need to calculate the diameter of the front tyre to prevent any problems with the front wheels synchronising with the rear wheels.

This preponderance rule allows for a tolerance of 0 to 3%. Within this range, preponderance will be optimised and your tractor will be able to unleash its full power, as its drive shafts will be working in perfect harmony.

 

The consequences of incorrect preponderance

What happens if preponderance is higher than 4-5%?

The rear axle will slow down the tractor's front axle, and the front axle assembly will be subjected to excessive mechanical stress. You will experience problems when steering, and your front tractor tyres will get worn much quicker than the rear ones.

What happens if the preponderance is negative and less than 0%?

The rear axle will push your tractor's front axle and the front shaft will lose its efficiency, the transmission will be damaged and you will have a lot of slip at the rear.

Consequence of a poor preponderance
Consequence of a poor preponderance

 

How to calculate your preponderance

This is a relatively simple calculation. First off, find the value given for the "Front axle mechanical ratio" by your tractor's manufacturer.

Next, apply the following formula:

(Circumference of the front bearing - multiplied by - Front axle mechanical ratio – minus - Circumference of the rear bearing) divided by - Circumference of the rear bearing - multiplied by 100

For example:
  • if the rear mount is: in 650/75/R38 with a rear bearing circumference of 5760 mm;
  • the front mount used is: in 600/65/R28 with a front bearing circumference of 4450 mm;
  • the mechanical ratio of the tractor's front axle assembly is 1.325;
The preponderance calculation will be as follows:
((4450 x 1.325) - 5760) / 5760) x 100 = 2.36%

In this example, the preponderance is correct and the tractor's efficiency will be excellent with larger wheels than those originally supplied.

 


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

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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.