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Agriculture

  • 1. What is the difference between a radial and a diagonal or cross-ply tyre?
    The main difference between radial and diagonal or cross-ply tyre is in the construction. A radial tyre is built around a carcass where the layers of ply go radially, from bead to bead. The tread is then strengthened with belt pockets. The sidewall of a radial tyre is softer than a bias tyre providing high comfort for the operator and less heat build up.The soft and flexible sidewall, in combination with the belts, gives a large contact surface and low rolling resistance.
    A diagonal tyre is built around a carcass where the cord path is diagonal, from bead to bead. The different layers of ply cross each other in opposite directions, which most importantly makes the tyre stiff, but strong, and gives the tyre a small contact surface and a high rolling resistance.
  • 2. What does ply rating mean in diagonal or cross-ply tyres?
    Previously, it indicated the number of layers of cotton canvas used in the CARCASS. With the new cable materials (nylon, polyester, steel, etc.), the actual layers are lower than stated.
  • 3. What is the load index?
    The load index is a numerical code associated with the maximum load that a tyre can support based on the speed (indicated by the related symbol), and in-service conditions as specified by the tyre manufacturer. It can be found on the tyre's sidewall, listed after the tyre size information.
  • 4. How do I compare the load index with the PR number?
    The load index, reported on the tyre's sidewall, identifies the load that the tyre is designed to withstand at the pressure specified by the company. Today's load range / ply ratings do not count the actual number of body ply layers used to make up the tyre's internal structure, but indicate equivalent strength compared to early diagonal-ply tyres. In all cases, when changing tyre sizes, or switching from one measurement type to another, it is important to confirm that the load index in the service description of the new tyre is equal to or greater than the load index of the original tyre, and / or that the nominal load capacity of the new tyre is sufficient to support the vehicle's gross axle weight values.
  • 5. What does IF mean?
    IF means Improved Flexion. An IF tyre can support higher loads at the same inflation pressure when compared to a non-IF tyre, or it can support the same load with 20% less inflation pressure.
  • 6. What does VF mean?
    VF means Very High Flexion. A VF tyre can support higher loads at the same inflation pressure when compared to a non-VF tyre, or it can support the same load with 40% less inflation pressure.
  • 7. What are the differences between NOMINAL, RECOMMENDED and APPROVED RIMS?
    NOMINAL RIM: it is the rim size indicated by ETRTO (European Tyre and Rim Technical Organization)
    RECOMMENDED RIM: it is the rim size that Trelleborg uses to develop and test a new tyre (written indication in the official Trelleborg Technical Manual).
    APPROVED RIM: this is one or more additional rim sizes that can be used with the same tyre.
  • 8. Can I use the same rim for both a non-IF and IF (Improved Flexion) tyre?
    Yes, although not always. In some cases, you may need a wider rim to get better tyre performance and also to increase road safety. If it is possible, you will find the note NRO (Narrow Rim Option) next to the size, in our technical manual.
  • 9. What does FRONT mean?
    The term FRONT indicates a tyre which is to be mounted on the non-driven axles of agricultural and forestry tractors. The tyre tread generally consists of circumferential grooves and ribs.
  • 10. What does IMP mean?
    IMP means a tyre designed primarily for towed equipment or agricultural trailers. It can also be fitted on the steer wheels of agricultural tractors, but is not suitable for high torque services.
  • 11. What does IND mean?
    IND indicates a tow wheel tyre for construction vehicles, with load and pressure capacities that differ from tyres of the same size used for agricultural tractors.
  • 12. What does MPT mean?
    MPT refers to a special purpose tyre designed for multipurpose trucks, on and off-road, and for agriculture.
  • 13. What does NHS mean?
    NHS refers to a tyre designed primarily for use off public roads, but also suitable for temporary or occasional use on public roads.
  • 14. What does the abbreviation SB mean?
    SB means Steel Belt. This means that the tyre has a steel belt instead of a fabric one.
  • 15. How can I chose the correct pressure for my agricultural tyres?
    You can find the optimal tyre pressure in the technical manual, which takes into account the product, size, application, speed and load applied to the tyre. Alternatively, you can use the Trelleborg Load Calculator or the Tyre Book Apps (the free applications for smartphones and PCs that allows you to calculate the necessary pressure quickly and easily).
  • 16. What is the tractor Front Lead value?
    The Mechanical Lead, or Front Lead is the relative percentage ratio between the peripheral speeds of the front and rear tyres. Commonly, the correct advancement of a four-wheel-drive tractor provides a Front Lead value between +1% and +5%. The positive value provides good steering ability, and in these conditions, the front wheels pull the tractor.
  • 17. How do you measure the rolling circumference on the field?
    The measure must be calculated in the following way:
    - remove the double traction (the rolling of the front and rear wheels have to be independent)
    - mark the front and rear tyres sidewall, on the middle of the tyre-foot print area
    - mark the rolling surface corresponding to the middle of the tyre-foot print area
    - move the tractor forward so that the front and rear tyres complete exactly 5 revolutions
    - mark on the rolling surface the point at the end of the 5th revolution, respectively for both the front and rear tyres
    - measure the distance crossed respectively to the front (f) and rear (r) tyres

    - CALCULATION OF Cr (front) = F[m] / n° of revolutions = a / 5
    - CALCULATION OF Cr (rear ) = R[m] / n° of revolutions = p / 5
  • 18. How do you measure the mechanical ratio on the field?
    The measure must be implemented in the following way:
    - insert the double traction
    - mark the front and rear tyres sidewall, on the middle of the tyre footprint area
    - move the tractor forward so that the rear tyre completes exactly 5 revolutions
    - count the complete number of revolutions of the front tyre

    - CALCULATION OF Cr (front) = F[m] / n° of revolutions = a / 5
    - CALCULATION OF Cr (rear ) = R[m] / n° of revolutions = p / 5
  • 19. What is ETRTO?
    ETRTO stands for European Tyre and Rim Technical Organisation. It encourages the alignment of national standards and the achievement of interchangeability of tyres, rims and valves in Europe with regards to fitment and use. It establishes common technical dimensions, load / pressure characteristics and operational guidelines. It promotes the free exchange of technical information relating to tyres, rims and valves. ETRTO works in liaison with the International Organisation for Standardisation - ISO - to develop relevant standards.
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