TECHNICAL INFORMATION
about retreading process

Discover all steps of our exclusive retreading process

+ General information

+ The different processes

+ The basis of Nordic Tires

+ Production of Nordic Tires

+ Performance validation

snowcross-process

General information

To build up an truck tire in the size 395/85R20, approximately 110 litres oil is needed in order to produce synthetic rubber compound, carbon black and others specific oil components.

The natural rubber (about 30% of mass) is shipped halfway around the world to be processed in Europe. There is also 60 kg steel cord used for this tire, sourced from the mining industry. A lot of energy is necessary for the steel and coating production.

An optimistic CO2 balance sheet for this kind of process would mean around 350kg CO2 for a steel cord tire in the weight class of 100 kg.

During the period of use of a truck tire, only around 15% of mass (tread) will be consumed. When the tire is used in a professional way, a quality casing has potential for a second service life. The life span of the tread makes a second service life possible.

All premium manufacturers of truck tires promote and sell the 4 life concept for a new tire to their customers. This concept includes regrooving, hot retreading and finally regrooving of the retread tire. This approach is very interesting in terms of cost reduction per km and the CO2 balance is noticeable enhanced.

Thus, a good casing has a residual value, and would therefore mean that a demounting after only one life cycle would automatically lead to a bad economical situation and also a bad CO2 balance. We can easily say that high quality casings, depending on use, are able to reach a life span over a half million of kilometers!

Unfortunately the image of retread tires is not so positive and in our consumer society, new products are always preferred. The vision of separated treads on road sides made retread tires unpopular. The consumer is not aware that such failures are the results of a economical retread process done by low quality companies. In this industry, there are unfortunately some black sheep who provides bad quality on the market and create bad reputation for retread tires.

From an ecological point of view

A large usage of retread tires for suitable transport systems, could enhance the CO2 balance substantially!

CO2 and other emission

New tire
Retreated tire

The different processes existing in the retread industry

 

Technically, the retread process of a tire consists of replacing the wearied rubber layer on the tread with a new one in the same quality and with the same characteristics. Before starting this process, the casings have to be carefully checked and the rubber must be buffed from the tread area or from bead to bead (omega retreading) and on a second stage be recharged with rubber compound. Generally there are 2 processes existing:

cold-tireCold retread process

This process consists to use a vulcanised and designed rubber band which is stacked on the casing. The sidewalls of the tire are not renewed. The next step is then to place the tire in an autoclave oven and to be heated in order to accelerate the vulcanising process. This kind of process does not allow a strong pressure from the rubber band (tread) on the casing. The push of the tread against the casing will be reached only through the under pressure in the autoclave. In this way, they are 2 difficulties to be managed in order to get a good quality:

  • The exact positioning of the tread band on the casing in order to reach a constant and stress less put on of the tread band so that during the cooking process a good cohesion can be reached.
  • A very careful assembly of the ends of the tread band. On this seam area, the risk of a separation during use is the highest.

The cold retread is mainly used for slowly running tires. This process does not need expensive tools machinery like a mould or a cooking press. This process is therefore easier subject to bad work of non-skilled companies. Tires from this kind of manufacturers are in general damaging the reputation of retread tire.

hot-tireWarm or full mould retread process

This process is globally very different to the previous one. First, the casing is covered with raw rubber. The rubber layer put on the tread is smooth without profile. The reconstruction of the casing with new rubber can be done only at the tread area of the tire or around the casing, that means from bead to bead in case of the warm omega retread process.

The rubber can be applied cold in form of one plate. The best-in-class and more performing way is called orbitread process. This modern process uses a thin hot and plastic rubber band which is wrapped on the casing. After that, the processed casing is placed in a mould which has been developed specially and adapted for the type and brand of the casing.

With the reconstruction of the casing through the orbitread process, no seem needs to be created at the tread area because of the multi layers wrapping. Furthermore, the cohesion between the applied rubber and the casing is more efficient because while the cooking stage, the piled up rubber layers are strongly pressed against the casing through an inflated tube or blade inside the tire.

The basics of Nordic Tires

A casing in good condition is the first requirement to produce a reliable and performing retread tire. Therefore, our procurement of casings is done according strong criterias:

Only casings in very good condition having not been used outside of Western Europe or on construction or recycling sites are selected.

No casings with punctures, chemical, thermic or others damages

Especially the beads must be in top condition for an further reliable fitting as tubeles.

The production date is always checked: not older than 6 years or with visible ozone crackings.

Exclusive selection of Michelin XZL, XZL2, X-Crane casings.

The sourcing and production date of every casing is verified. The customer can also get SnowCross tires build up on basis of his own casings. After the delivery to our factory, the casings are checked on 2 levels: a first optical control at check-in and later in production after the buffing process, when the skin of the casing is visible and touchable.

case-rejected
case-validated

Production of Nordic Tires

 

In order to fulfill the high level of performance requested for fast going firefighting trucks, Nordic Tires are only produced with the most appropriate and performing process in the retread industry.

Step 1 – Buffing of the casing by machinery

In order to take away the old rubber and to prepare the casing for coating with new rubber, the tire is buffed. This step is similar to metal processing and done by a modern computer steered machinery. Picture 3: The contour of the buffed casing is checked on 3 positions around.

Step 2 – Control of the buffed casing with final validation for reconstruction

After the buffing process has not detected inside damages which could appear, the uncovered casing is carefully checked in order to detect smaller punctures, air bubbles and rust, chemical or thermic damages. Then, the buffed and validated casing is wrapped in a film in order to avoid contamination during transfer to the next station.

Step 3 – Reconstruction or recharging by Orbitread

The casing is fit on a CNC machine called Orbitread in order to execute the recharging of tread and sidewalls. An extruder machine leads the hot and flowing rubber band to the casing. The speed of wrapping and the applied rubber mass is monitored by computer to get a uniform covering. During wrapping the pile up rubber band is pushed on the casing with rolls in order to avoid air bubbles and to obtain a quick and uniform sticking.

A hot and flowing rubber band coming from the extruder machine is wrapped on the casing. The rubber put on the tread is an abrasive resistant high quality rubber from Kraiburg which is made in Germany.

Europress system with radial working segments

Step 4 – Cooking of the raw tire

The raw tire is processed exactly in the same way than during the production of new tires: put in a mould and vulcanised in a cooking press. After approximately 2 hours, the vulcanising process is achieved and tire is extracted from the mould. It’s exactly looking like a new tire!

Validated retread performance of Nordic Tire

Nordic Tires are produced with the best-in class and latest innovative process for hot retreading and have the same speed index as the original tire. Nordic Tires fulfill the ECE R109 Standard for retreaded truck tires.

In addition, the tires fulfill higher internal speed requests in order to cover the specific speed requirements for firefighting vehicles in service on private airfields.

At ambient temperature between 20 – 25°C:

  • 1 hour running at 100% load / 90 kph / 8.5 bar
  • Followed by 3 simultaneous accelerations from 0 to 130 kph and holding the maximum speed during 2 minutes