In wet conditions, work in the fields can easily become problematic when you don’t have the self-cleaning capacity of your tractor tyres or implements under tight control.
Slip effectively always begins with too much earth accumulating between the tyre lugs without you really knowing why. Yet when you start to slip, working gets complicated, the tyres seal over the soil, there is loss of traction and the steering is less responsive. In short, work slows down and if the weather conditions get worse, the situation can turn into a nightmare with the risk of getting stuck in the wettest parts of your field.
In reality, by taking a few simple precautions, you can considerably improve your tyres’ self-cleaning capacity and avoid slip, even if the earth is heavy, as we explain in this article:
1. What are the consequences of inadequate self-cleaning for tractor tyres?
The agricultural tyre is the only direct contact between your tractor and the ground. If it does not self-clean properly, the consequences may be multiple and could be very damaging for your productivity, such as excessive slip for example and sealing of the arable soil layers.
Excessive slip slowing down work
1. Increase in slip ratio
Your agricultural machine’s tractive effort depends on several factors, among which is the slip ratio. A little slip is actually necessary to facilitate the transmission of tractive force to the ground. The slip ratio should be between 8 and 12%, because above a certain limit, around 30%, you will be obliged to stop working or risk seeing your trailer completely bogged down.
To be exact, slip is linked to a combination of different factors, the first of which being the accumulation of earth between the tyre lugs. If you are faced with the following situations and you don’t know how to compensate for a poor self-cleaning capacity, you are likely to notice a rapid increase in the slip ratio:
Difficult weather conditions
Excessive slip is often linked to bad weather conditions which may influence the structure of your soil, in particular in the event of persistent bad weather or a high level of humidity. Wet ground is effectively more slippery and will demand an optimal tractive effort and tyres with lugs developed to reduce the accumulation of earth and avoid slippage.
A specific type of soil
The nature of your soil is a factor to check before starting work, especially if you transport heavy loads. You must begin by analysing the condition and type of soil on your land to avoid the risk of excessive slip. If the soil is slightly damp and crumbly, with nice weather conditions (light, soft soil) you can work normally.
On the other hand, don’t hesitate to postpone operations when the earth is too wet and sticky, because slippery ground leads to a high level of slip which is likely to result in your wheels getting clogged up. There could be major consequences for your wallet, because in addition to losing time, you must take into consideration the increase in fuel consumption, premature wear to your tyres and loss of future yields.
An unsuitable tyre model or tyre size
In certain cases, the model or type of tyre that you use will be a factor in slippage. Here are the most frequent cases:
- Your tractor’s original tyres correspond to a classical tyre which is an economic solution for the tractor manufacturer, but certainly not the model of tyre that is best suited to your specific situation. Your type of farm, the size of your fields, the earth in your region and your local weather conditions must be taken into consideration when choosing the most suitable tyre for you.
- Tyres that are too small compared to your load or your implements require higher inflation pressure to compensate, which can generate an accumulation of earth between the lugs and excessive tyre slip.
- A tyre structure that is not appropriate for the work you have to do, for example, diagonal or bias ply tyres for field crop farming will be less suitable. They are more rigid and therefore less efficient for self-cleaning than radial VF tyres, which are far better for avoiding slip.
Diagonal structure tyres are less efficient for self-cleaning
Inflation pressure linked to weight but ill-adapted to the type of soil
Many farmers tend to increase inflation pressure in their tractor tyres when they work with heavy implements in the fields, with the aim of limiting the excessive crushing of the tyres.
Unfortunately, this practice is not recommended, especially in wet conditions, because overinflated tyres sink deeper into the ground to get a better grip. This increases rolling resistance, the accumulation of earth on the tread and therefore increases the slip ratio.
2. A waste of time cleaning mud on the road
During the autumn and the start of winter, end of season harvests such as sugar beet, potatoes or carrots require agricultural convoys which go from field to road in the rain and which can leave the roads muddy.
When the weather is unkind and the earth is sticky, the tyres’ self-cleaning capacity is crucial. If your tyres are properly set up with a relatively light accumulation of earth, you save time on the cleaning of your wheels and roads.
If the earth accumulates on your tyres, the road may become much more slippery at the place where you enter and exit your agricultural site and cause accidents for other road users.
3. Soil erosion
The use of low-cost tyres may have a negative effect on the quality of your soil. Generally, this type of tyre does not have lugs that have been studied to reduce soil disturbance.
Standard tyre studs effectively cause soil displacement, by lifting up the earth and carrying off the best part of the arable layer on the surface. This phenomenon is worse in wet conditions. Unfortunately, soil compaction and sealing accelerate erosion, thus damaging the condition of your field.
Soil erosion linked to unsuitable work in wet conditions
2. What are the principles of self-cleaning
Depending on the type of soil and the type of tyre, one or the other may lose its shape separately.
- If the soil is soft but your tyre is rigid, it’s the soil which changes form to fit the shape of the tyre studs. The earth stuck between the lugs is packed, which is what is known as horizontal compaction. This compaction makes it possible to find the resistance point to transmit torque to the rim and obtain good traction. However, the rigidity of the tyre will not allow the earth accumulated between the lugs to evacuate correctly when the lug leaves the ground. More earth collects between the lugs on each rotation of the wheel, leading to more slip.
- If the soil is soft but you work with supple tyres, such as VF agricultural tyres whose casing is sufficiently flexible to work at low pressure. The tyre flattens more on contact with the ground and increases its soil footprint, then during its rotation the casing recovers its initial shape and by doing so pushes the earth out from the lugs. It’s the systematic changing of shape with every wheel rotation that makes it possible to free the earth as soon as the tyre leaves the ground and which improves self-cleaning.
3. What are the main techniques to improve self-cleaning
There are ways to improve the self-cleaning capacity of agricultural tyres:
Choose the right inflation pressure
Overinflating your tyres when you work in the fields merely increases rolling resistance, and as such soil compaction and slip, above all in wet conditions. By driving with a high inflation pressure, your tyre’s casing becomes rigid and evacuates less earth.
Ideally you should set the right inflation pressure for your tyres to obtain an ideal slip ratio and optimal motricity. By doing this, you improve the self-cleaning capacity by reducing slip and as a result you also reduce your fuel consumption.
Change in tyre pressure test in the same field
on the left 1 bar = no slip,
on the right 1.25 bar = excessive slip
Choose tyres with a better tread construction
Standard or low-cost tyres have single studs whose only purpose is to participate in the tractor’s tractive force.
If you wish to optimise your productivity and improve self-cleaning, you should look for specific tyres whose lugs have been developed as a result of research and development work.
At Bridgestone, you will find tyres whose lug design is the result of thousands of hours of studies. The lugs are rounded rather than straight to optimise the form of the leading edge, to improve penetration into the earth, optimise traction and reduce soil displacement when the lug leaves the ground.
These lugs have a curved structure with multiple angles, including two dedicated to major roles: one angle for traction, the other for self-cleaning.
On a Bridgestone VF VT-TRACTOR tyre
1. Angle which is designed for traction
2. Angle which is designed for self-cleaning
4. The advantage of VF technology tyres
For optimal work in the fields in wet conditions, it is better to opt for innovative VF tyres. They offer the best compromise between optimal self-cleaning and maximum tractive effort. These latest-generation tyres are designed using resistant materials and with flexible, reinforced sidewalls which means that they can operate at a very low inflation pressure.
Whatever the load transported and whatever the type of soil, VF technology tyres make it possible to increase the soil footprint and as such the tractive effort. As the shape of the casing changes completely when the tyre leaves the ground, the earth is ejected easily, which improves self-cleaning.
VF agricultural tyres have a tread with lug angles that have been studied closely and which guarantee maximum cleaning of the surface of the tyre when it leaves the ground. Thanks to the larger contact patch with the ground, you will have better control of slip while improving your tractive force.
The Bridgestone-agriculture.eu blog is written and administered by tractor tyre experts who are available to provide you with the advice you need on the subject of your agricultural tyres. They allow you to maximise your productivity with information on all subjects linked to tyres: Cheap tractor tyres — Technical data for agricultural tyres — Air pressure advice — Solutions to avoid soil compaction — Sprayer tyre pressure — Why and how to ballast your tractor tyres — When to use dual wheels — The mechanical causes of abnormal wear — Cheap agricultural tyres – etc…
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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This information is intended only to make you aware of the technical and functional aspects of agricultural tires and their use. It does not allow you to make a judgment or a definitive conclusion on a given problem. Only your agricultural tire expert is able to make a technical assessment and take a final decision, case by case.
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