FAQ

The main difference between radial and diagonal or cross-ply tire is in the construction. A radial tire 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 tire is softer than a bias tire 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 tire 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 tire stiff, but strong, and gives the tire a small contact surface and a high rolling resistance.

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.

The load index is a numerical code associated with the maximum load that a tire can support based on the speed (indicated by the related symbol), and in-service conditions as specified by the tire manufacturer. It can be found on the tire's sidewall, listed after the tire size information.

The load index, reported on the tire's sidewall, identifies the load that the tire 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 tire's internal structure, but indicate equivalent strength compared to early diagonal-ply tires. In all cases, when changing tire 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 tire is equal to or greater than the load index of the original tire, and / or that the nominal load capacity of the new tire is sufficient to support the vehicle's gross axle weight values.

IF means Improved Flexion. An IF tire can support higher loads at the same inflation pressure when compared to a non-IF tire, or it can support the same load with 20% less inflation pressure.

VF means Very High Flexion. A VF tire can support higher loads at the same inflation pressure when compared to a non-VF tire, or it can support the same load with 40% less inflation pressure.

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 tire (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 tire.

Yes, although not always. In some cases, you may need a wider rim to get better tire 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.

The term FRONT indicates a tire which is to be mounted on the non-driven axles of agricultural and forestry tractors. The tire tread generally consists of circumferential grooves and ribs.

IMP means a tire 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.

IND indicates a tow wheel tire for construction vehicles, with load and pressure capacities that differ from tires of the same size used for agricultural tractors.

MPT refers to a special purpose tire designed for multipurpose trucks, on and off-road, and for agriculture.

NHS refers to a tire designed primarily for use off public roads, but also suitable for temporary or occasional use on public roads.

SB means Steel Belt. This means that the tire has a steel belt instead of a fabric one.

You can find the optimal tire pressure in the technical manual, which takes into account the product, size, application, speed and load applied to the tire. Alternatively, you can use the Trelleborg Load Calculator or the Tire Book Apps (the free applications for smartphones and PCs that allows you to calculate the necessary pressure quickly and easily).

The Mechanical Lead, or Front Lead is the relative percentage ratio between the peripheral speeds of the front and rear tires. 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.

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 tires sidewall, on the middle of the tire-foot print area
- mark the rolling surface corresponding to the middle of the tire-foot print area
- move the tractor forward so that the front and rear tires 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 tires
- measure the distance crossed respectively to the front (f) and rear (r) tires

- CALCULATION OF Cr (front) = F[m] / n° of revolutions = a / 5
- CALCULATION OF Cr (rear ) = R[m] / n° of revolutions = p / 5

The measure must be implemented in the following way:
- insert the double traction
- mark the front and rear tires sidewall, on the middle of the tire footprint area
- move the tractor forward so that the rear tire completes exactly 5 revolutions
- count the complete number of revolutions of the front tire

- CALCULATION OF Cr (front) = F[m] / n° of revolutions = a / 5
- CALCULATION OF Cr (rear ) = R[m] / n° of revolutions = p / 5

ETRTO stands for European Tire and Rim Technical Organisation. It encourages the alignment of national standards and the achievement of interchangeability of tires, 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 tires, rims and valves. ETRTO works in liaison with the International Organisation for Standardisation - ISO - to develop relevant standards.