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Retread Tires

03/05/2013

Retread Tires?


In a retread tire the worn tread is replaced with new material having the same characteristics as the original one. Retreading is possible because the tire structure has a much longer useful life than the actual tread. This procedure is governed by strict technical regulations:
- ECE ONU 108 for motor vehicles
- ECE ONU 109 for commercial vehicles
Approval of retread tires that come in the field of application of the above mentioned regulations, is mandatory
This process entails different phases.

Preventive selection
In order to ascertain suitability each tire is subject to a tactile/visual inspection by an expert with the aid of instrumental tests such as the shearography.
 
Buffing
This operation removes the remaining old tread and prepares the surface in readiness of the new tread.

Casing inspection and repair
The casing is inspected once again after buffing and any repairs needed are seen to.

Applying liquid rubber
A layer of liquid rubber is applied that prepares the surface for receiving the new material.

Applying the new tread
With the hot technique
The casing is mounted on a rotating machine that applies a new band of raw rubber without any pattern.
With the cold technique
A pre-impressed, vulcanised tread is applied on the casing. The tread is available either as a band or in the shape of a closed ring. Besides the flat bands there are also those with side “wings” for joining their profile to that of the sides of the casing.

Vulcanisation
With the hot technique
The tire prepared with a plain profile goes inside a vulcanising press equipped with a mould with pattern that is impressed on the tire. The press has a device to adjust the time, temperature and internal pressure. When the necessary time has elapsed (which varies according to the size of the casing and the thickness of the tread) the air is discharged and the tire can be taken out of the mould.
 
With the cold technique
The tire is mounted on a machine that applies envelopes. Vacuum is created in order to eliminate any air left between the envelopes and the tire prepared with the pre-impressed tread. The tire then enters an autoclave for vulcanising. “Baking” time normally takes: 2.5 - 3.0 hours. Temperature is approximately 110°C.

Checking and finishing
When the retread tire is taken out of the vulcanising press or autoclave it undergoes a final internal and external test and is checked under pressure by specific machines.
Lastly it is given the finishing touches.

Retreading tires is good for the environment (compared to the production of a new tire; with this recycling procedure 70% of energy is saved and the flow of used tires to dispose of slows down) and for your wallet! So why not retread?