THE SECOND LIFE OF THE TIRE

Round, so it can roll, and elastic, so it can cushion: the tyre is the only point of contact between the vehicle and the ground. The proper functioning is guaranteed by a structure made of composite materials, which are held together by a complex industrial process that puts together around 200 different raw materials to manufacture a semi-finished product. The proportions of mixtures vary according to the type and purpose of the tire.

As we have already explained in the post "The quality of the retreaded is no less", the structure of a tire has a much longer lifetime than the tread, and this is the exact reason why it is possible to give a second life to the tire. In this regard Salvadori is the world leader in the sector with its history of innovation, research and excellent customer care counting more than 35 years. Salvadori takes care of the entire life cycle of the tire: it manufactures and distributes products for tire retreading, tire repair and tire service, without overlooking finished products made of recycled rubber.

But how is a tire retreaded? The standardized procedure that leads to the "rebirth" of a tire is divided into seven phases. The manufacturing process makes use of high-tech machinery and of materials largely similar to the original ones in order to completely restore the original functionality of the used tire while guaranteeing its reliability and safety.

The first phase is the INSPECTION. It consists in evaluating the load-bearing structure of the tires that at the end of their first life have used up a few millimetres of tire tread (20%). First a VISUAL analysis of an expert technician, then an ELECTRONIC one through NDI® technology to examine the internal structure of the casing and to reveal any defects invisible to the naked eye.

The second phase is BUFFING, which is needed to remove the old and worn tread. Once completed, a further inspection of the casing, and if necessary, additional repairs are carried out. If the injuries turn out to be too large, the casing is dismissed.

During this second phase air buffers, buffing mediums, grinding stones, brushes and carbide cutters are used to perform the repairs, extruder guns are used to fill possible craters, and buffing blades, like our TOP RUBBER, are used to remove the old tread.

Subsequently a layer of cushion gum is applied to prepare the surface for the application of the new material.

The next step is TREAD APPLICATION, one of the most important phases of the retreading process. It can be done in one of the two ways. The HOT PROCESS means that the casing is mounted on a rotating machine that applies a new strip of non-vulcanized rubber without a pattern. During the COLD PROCESS first a layer of cushion gum is applied on the casing and on top of it goes a tread in strips or circles, depending on tire size and design. The choice of the material to be applied depends on the use of the tire and is also the result of multiple year experience in the selection of suppliers.

The casing, covered with new materials, undergoes the CURING process, at appropriate temperature and pressure. Also in this case it is possible to proceed in a HOT or COLD way. In the first case the tire is placed in a press, inside which there are sectors with the design chosen for the tread. The tires are left inside at a certain temperature for a certain period of time. During the hot process curing tubes and bladders are used.

A COLD curing process, on the other hand, requires the casing with the new tread to be placed in an envelope, which can be inner and outer (double system, as in the Salvadori ALL-IN line) or only outer with the application of a ring (ARC Ring system). This is necessary to create a vacuum effect that is to remove the air and create pressure on the tread. Afterwards the tires are placed into an autoclave, where the combination of time, temperature and pressure leads to the curing of the cushion gum and creation of a bond between the new tread and the tire.

The FINAL INSPECTION represents the last phase in the continuous chain of quality controls carried out throughout the retreading process and aims at verifying that the finished tire meets all the technical and aesthetic specifications required by the quality standards. The tires thus returned to new life can also be repainted and labelled to give a "fresh" appearance.

It is worth noting that, after the pioneering period of the 1950s, today a retreaded tire satisfies the same safety standards and possesses the same functional characteristics as a new one. In fact, a retreaded tire must undergo the same tests that are obligatory for new tires, and that is imposed, firstly, by rigid standards of Italian regulation UNI 9950 of September 1996 and then by UNECE Regulations 108 (retreaded tires for passenger cars) and 109 (retreaded tires for commercial vehicles) of June 1998.