Tractor tyres are pushed to the limit and we demand a great deal from them for activities which are not always straight forward. Use in the farmyard or in woodland that has to be cleared is always possible, but as each tyre is designed for a specific use, it is not always adapted to other types of use. Work that is too hard can lead to invisible injuries which may turn out to be destructive for the tractor.
When you see a small hernia appear on the sidewall of your tractor tyre, you may legitimately consider that it’s not too serious, because in general it is small and confined, so it’s easy to imagine that it won’t cause any more problems than a small cut.
In this article we will look at the real consequences of a hernia on a tractor tyre.
First of all, you have to understand how an agricultural tyre is designed
Each agricultural tyre is the fruit of an elaborate combination of rubber and different components. Layers of woven nylon are incorporated in the rubber to increase its resistance to pressure while retaining its suppleness. It is this specific woven form that protects your tyres against a possible hernia, because it constitutes a tight mesh netting which perfectly contains the inner tyre pressure.
Comes from the coagulation of latex obtained by rubber tapping. Qualities: elasticity, adherence, resistance, impermeability.
Butadiene: this is mixed with the rubber to improve its resistance to wear, to impact, to heat, etc.
TREAD before heating process
Functions: pull, resist cuts, protect, provide comfort, stabilise and steer.
The lugs are formed during the vulcanisation process.
SIDEWALL before heating process
Functions: ensure supplenes, stabilise, absorb shocks, protect from cuts.
The markings are formed during the vulcanisation process.
CASING or INNERLINER
Functions: contain the air, resist load, maintain pressure, absorb shocks, provide comfort.
Functions: absorb shocks, protect, maximise the tyre footprint, steer.
There are 2 types of ply: casing ply and stability ply.
You might wonder if using a design based on woven layers of steel rather than nylon would provide a more solid solution. Manufacturers have effectively made this choice for some tyres that need to withstand very severe pressure, but this type of structure was not chosen for agricultural tyres, because there is a clear lack of flexibility.
There is therefore a mismatch between a tyre whose construction is too rigid, too compact and the suppleness necessary to preserves soils and land and avoid excessive, deep compaction which is detrimental to crops and therefore to your productivity.
The structure of a radial tyre was designed for a better distribution of load to the ground, but also to strengthen the parts that are most in contact with the ground and retain some suppleness in the parts which are not in contact with the ground, thus providing the necessary flexibility for quality work.
The radial structure is made up of layers of fabric which run perpendicular to the direction of travel of the wheel. They make up the structure of the sidewalls and the in-depth structure of the tyre following which this base was reinforced by overlaying layers on the tread to ensure its resistance to the tyre on the contact patch with the ground. This gives the tread a very high level of resistance compared to the sidewalls which remain supple.
1. How is a hernia caused?
The structure made up of several textile layers within the tyre is highly resistant but still has limits, above all faced with a violent impact in the following situations:
- Impact of a natural object like sharp stone, a root or branch when you drive along paths or in your fields.
- On the road at greater speeds when you encounter potholes.
- Metallic objects in the farm courtyard, tools, edges of other machines…
- Sharp objects hidden by the crops, thrown by car drivers from roads by the side of the fields…
- Impact or accident with another agricultural vehicle during manoeuvring for example.
In all of these situations the impact leads to a break in the internal structure of the tyre, without showing any cut on the outside.
It’s imperceptible, above all when the impact is on the tread, for example, with stones or roots. You will only find out afterwards if there is a problem, when setting tyre pressure for example.
You may see a bump appear on a part of the tyre, generally on the sidewalls, because the tread is reinforced.
This "bump" means that the internal meshing of the tyre has been altered, the air which is required to maintain the tyre pressure escapes due to this break in the mesh and is only kept in by the tyre’s rubber.
The impact has brought about a weakness in the structure, with certain threads of the mesh certainly broken. The internal air pressure is no longer contained within the structure of the tyre and deforms the rubber layer which offers the last layer of defence before an air leak.
A what moment are we most likely to see a hernia appear:
- During pressure build-up if you equip your tractor with heavy tooling.
- When driving on the road at speed and loaded, the temperature within the tyre may rise to 65 degrees, increasing the dilation of the tyres’ constituent materials.
- After the winter, when you take out your tractor to begin the season, putting pressure back into the tyres may reveal a hernia linked to an impact which occurred the previous season.
- When mounting the tyre with incorrect lubrication, if the tyre bead installation tool moves, it may cause a tear, leading to an infiltration of air between the casing ply and the sidewall rubber during inflation.
2. Can the hernia on my tractor tyres be repaired?
You may think that a mere bump on the tyre’s sidewall is not very serious, yet this bump is only the visible side of more serious damage at the level of the layers of fabric which modifies the internal structure of the tyre.
Generally, a hernia cannot be repaired, yet in specific cases, certain tyre merchants who specialise in agricultural tyres have the skills and the equipment to carry out hot "vulcanisation" repairs.
If repairing the tyre is not recommended, this is because the risk of the tyre bursting is considerable and it can happen at any time.
As soon as you detect a hernia, your tractor must be immobilised and a replacement tyre sought. Even when driving at a slower speed, a hernia may lead to bursting and immobilise your tractor or even cause an accident.
Hernia on the tread
There is no point in repairing a tyre following a violent impact to the tread. The repair will not be able to resist the slightest overinflation, an increase in speed on the road or even use with a heavy load.
As you can see in the images below, a hernia on the tread corresponds to a break in the tyre’s inner lining.
This deformation is linked to an internal break which necessitates the replacement of the tyre at all costs.
Hernia at the level of the bead
If the break is at the level of the bead, it cannot be repaired, above all if you can see the metal rods of the bead. The tyre must be replaced as there is no possibility of repair.
Bead cut during mounting, leading to a hernia at the level of the bead
Hernia at the level of the sidewall
This is perhaps the only case where repair work is possible, if the hernia is small and the impact clearly located at the centre of the sidewall between the shoulder and bead turn-up, repairs may be considered.
The appearance of the rubber on both sides of the tyre, inside and outside, must be inspected.
Dismount the tyre and look internally to see if you can find an area where the casing ply is broken.
- If the internal break is too extensive: the tyre must be replaced.
- If the break is visible internally but extremely limited: you can have the tyre repaired using the hot vulcanisation process and an internal repair patch while complying with vulcanisation standards. Any cold repair will not fix the problem, the hernia will always reappear.
3. What are the risks linked to repairs
When the internal structure of a tyre has been damaged, there are very few repairs that are likely to resist the pressure, increasing loads, the permanent flexion and deflexion which the tyre will undergo during operations. The internal temperature may rise to more than 65 degrees on the road with speed and you cannot rule out a further impact to the tyre in the same area, which is why it is generally recommended to change the tyre as soon as a hernia appears.
This is not just a possible option, because there is a real risk of the tyre bursting if the repair is not properly carried out, which would lead to immobilisation in the fields, often at the worst possible time, or an accident on the road if you are driving with a full load, with costs that are generally far higher than just replacing a tyre.
4. What are the solutions for avoiding weaknesses in my agricultural tyres
Always driving with the right inflation pressure is a good way of avoiding problems, especially when setting tyre pressure provides a simple and rapid opportunity to carry out a visual inspection of all the tyres to detect a hernia before heading off to work.
Always use a tyre that is adapted to the situation or work to be carried out. It will always be more prudent to take a few hours to change tyres before carrying out very hard work to preserve your machine and avoid the unnecessary cost of having to replace your top-of-the range tyres.
If you have an afternoon of clearing or deforestation work to do, it is much more productive to lose a few hours replacing your latest VF tyres, which are not suitable for this work, and preserve them by using tyres such as Forestry.
Tractor equipped with Forestry tyres
The more robust design of a forestry tyre, which is reinforced with steel belts, provides better resistance to perforation. Its highly resistant multi-layered fabric structure is extremely durable, with its enriched rubber lugs, its protective guard and reinforced casing, which give the sidewalls an increased shock resistance capacity, well above average compared to a standard tyre.
If you have an even tougher use of your tyres in the farm courtyard for feeding the animals with manoeuvring on hard surfaces, but you also wish to work regularly in the fields, you will need a tyre that is designed to be polyvalent, reinforced and which has a greater layer of rubber than average.
In most cases, this type of tyre will enable you to avoid hernias due to multiple impacts. The VX-Tractor tyre, for example, was designed with a new rubber component that is much more resistant to wear than the other tyres on the market. It has 20% more rubber in its lugs and its new, more resistant casing design is the fruit of a technology which allows for inflation pressure from 0.6 to 2.4 bar, which is perfect for adapting to each type of use and allows the heaviest loads to be carried.
Without totally guaranteeing you against impacts, a tyre that is more resistant overall and which is designed for harder work will minimise the risk of having to change tyre because of a small hernia.
To learn more about ways to increase your farm’s productivity, bridgestone-agriculture has created a comprehensive eBook on the topic which is available for you to download for free:
Bridgestone-agriculture Blog is written and administered by tractor tyre experts who are available to provide you with advice on agricultural tyres. They will help you to maximise your productivity with information on all things relating to tyres: inexpensive tractor tyres, technical data for agricultural tyres, solutions for avoiding soil compaction, sprayer tyre pressure, why and how to ballast your tractor tyres, when to use dual-wheels, the mechanical causes for abnormal wear, discounted agricultural tyres, etc...
Most people who read this article have also read some of the following articles:
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- Agricultural tyres: +37% wear due to misalignment
- The worst consequences linked to used tractor tyres on your soils
- Why do my front tractor tyres wear much quicker?
- How to limit agricultural tyre wear faced with heavy loads
- When does a split make it necessary to replace your tractor tyres?
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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.