What is TYRE RETREADING?
When a tyre loses a few millimeters of its tread it doesn’t have to be thrown away, but it has to be brought to a new life, as it still maintains its specific structural qualities unimpaired. Eliminating and replacing the worn out tread, the tyre can be given back features completely similar to the original one: in fact, the tyres retreaded according to the Ece Onu 109 regulations, compulsory all over Europe, suffer the same controls and resistance and quality tests as new tyres.
Therefore, retreading tyres means extending the life time of the product improving its yield in kilometers, valorizing the casing and exploiting completely the investment already done by the purchase of the new tyre. ln fact, the casing represents approx. 70% of the total value of a tyre.
Moreover, every year Customers choosing to use retreaded tyres save money and protect the environment. To build a truck tyre 70 kg of rubber are needed for the production of which 100 liters of oil are needed. If the tyre is not retreaded after its first use, this amount of raw materials would be lost through disposal. Instead, by retreading, it is re-covered in great part, adding only a limited quantity of raw materials to replace the worn out tread.
The problem of tyres disposal is particularly heavy; approx. 100 years are needed in order for one only tyre to get completely deteriorated and the impact of this procedure on the environment is highly harmful. Thanks to retreading, every year it is possible reducing the wastes production and avoiding the introduction to dumping of thousands of tons of used tyres.
The need to replace the tyres of circulating vehicles involves the need to get rid of approx. 180 million tyres per year in Europe (30 million in Italy only) with a negative impact on the environment that can be easily imagined. Retreading a higher number of tyres using frames which revealed to be still perfectly entire after accurate controls after the first use, allows to contribute considerably to safeguard the environment.
The technologies employed by our company for the manufacture of our machines always allow us to offer to the market high quality products.
Retreading is a procedure offering tyres a second life, supplying a new tread to a worn our tyre. This occurs by means of six essential passages:
- INSPECTION: it consists of an inside and outside analysis of the tyre in the aim to find aspect and structural faults, executed both by expert technicians and by the support of equipment technologically in the van.
- BUFFING: it is the operation by which the residual tread is eliminated from the casing.
- REPAIRING: in this phase eventual structural damages of the casing are considered and repaired, restoring the optimal conditions of the casing.
- BUILDING: by different treatments and the aid of automatic machines, the new material is applied onto the casing (rubber compound) to retread the new tread.
- CURING: the casing, complete with new materials, is submitted to the curing procedure to obtain the tread profile desired.
- FINAL CONTROL: this phase represents the last ring of the continuous chain of quality controls executed during the whole retreading procedure and it has the aim to check that the finished tyre responds to all technical and aesthetical speciﬁcations foreseen in our quality standards. Only when it got the corresponding approval, the tyre is given back to the Customer.
Hot retreading involves the vulcanisation of a tyre in a mould at a temperature of around 150 °C. The tread and the sidewall veneer of the tyre are made up of non-vulcanised rubber compounds. The shape and tread of the tyre are created in the heating press.
Arguments in favour of hot retreading:
- Suitable for all tyre applications, including car and aircraft tyres.
- Material costs are lower than the more complex products required for precure retreading.
- Hot retreading also allows extensive repairs to be carried out on the tyre carcass (e.g. belt replacement).
- Even bias-ply carcasses can undergo hot retreading without any problems.
Points to note:
- A separate mould is required for each tread and size. This requires a high level of investment in a range of moulds, which will be needed to be regularly updated.
- The production process needs to be designed for large numbers of tyres. This calls for a central production workshop, an extended customer area and therefore brings with it relatively high logistics costs.
Precure or “cold” retreading involves vulcanisation without a mould at a temperature of between 95 °C and 110 °C. The tyre is put together using a pre-vulcanised tread liner (= new tread) and a non-vulcanised bonding gum layer. The bond between the carcass, the bondung gum and the precured tread is created in an autoclave. Precure retreading has become fully established in the truck tyres sector since the introduction of radial tyres in the mid-1960s.
Arguments in favour of precure retreading:
- Less investment is required on the part of the retreading plant (no expensive moulds) and lower follow-up costs, since it is the material supplier who updates the range of moulds.
- A wide range of tread types are available, allowing the optimum tread to be selected for the tyre application.
- The comparatively low investment costs involved mean that decentralised, smaller production units can be operated. This means lower logistics costs and makes the operator more flexible and closer to his customers.
- The precure retreading process is kind to the carcass, since vulcanisation temperatures are lower and put less strain on the rubber-metal bonds in the carcass. Heat build-up in the tyre, rolling resistance and other tyre properties are often easier to assess than with hot retreading.
- With comparable tread geometries, the running performance of a precured retread is often better than a hot retread and the same as an equivalent new tyre.
Points to note:
- Precure retreading requires high-quality carcasses.
- Material costs are higher than hot retreading material, since the precured tread is already vulcanised and is therefore a more heavily-processed product.
- Labour costs per retread are higher than for hot-retread truck and bus tyres.