Retreading
extends the life of a worn tyre for re-use in its original
form by essentially
removing and replacing the worn tread. |
 The first step in the retreading
process is the selection of tyres (casings) suitable
for retreading. This operation is to find any damage
that would render the tyres unsuitable for retreading
and also to access the age of the tyre from it's
DOT number.
Tyres that are over age (7 years maximum) cannot
be retreaded. It is essential that only suitable
casings are accepted in accordance with current
quality standards.
 Tyres are mounted onto a machine specifically designed
to rotate and open the tyre's beads to enable visual
inspection, both inside and out.
After an initial visual inspection, the tyre is
then mounted onto a pressure testing machine where
the tyre is pressurised in stages to its operating
pressure.
A large percentage of tyres are rejected at this
point in the process.
If a tyre is determined as suitable for further
processing then it continues to the next stage where
the worn tread is 'buffed off' to accept a new tread. |
|
| The
Buffing Operation. |
 The purpose of the buffing operation
is to remove all residual tread from the casing.
At the same time the crown and shoulder of the tyre
are specially profiled to pre-determined radii and
dimensions.
Apart from the complete removal of tread pattern,
excessive undertread is also removed to restore
flexibility to the casing and help to eliminate
the possibility of overheating when in service.
This is achieved at Adco using the latest in computer
assisted buffing techniques.
Measurements typed into the computer are used by
the buffing machine to guide the buffing head across
the surface of the tyre, realising an accurately
buffed radius and optimising the shape of the finished
retread to enhance performance, reliability and
wear. |
|
| Casing
Preparation. |
 Post buffing, the buffed surface is then prepared to
receive a new tread.
Cuts and scores to the crown and sidewalls are individually
buffed out, and rubber in solution applied to the
whole tread area.
Where necessary, rubber compound is extruded by
way of a hand extruder filling in repaired areas,
and reinforced repair units fitted.
A layer of bonding rubber is then built onto the
prepared surface leaving the tyre ready for the
next stage - building the new tread on. |
|
| Tread
Building. |
 The process Adco
have adopted is a 'Pre-cured' retreading process.
That is where the new tread is brought in already
pressed / moulded by our supplier, and these treads
are then built and cured onto the prepared tyre.
Since the treads are cured away from the tyre (ie
pre-cured) , then it isn't necessary to cure the
tyre at the higher curing temperatures required
to vulcanise tread rubber (typically 150°c),
and therefore a much lower curing temperature of
100°c can be used.
Finally, identification labels are placed on both
side walls indicating the manufacturer and standards
to which the tyre has been retreaded. |
|
| Curing
Process. |
 When the treads
are built onto the tyre, the tyre is then placed
inside curing envelopes where the assembly is vacuumed
and loaded by way of a mono-rail system into an
autoclave (pressure vessel), and cured.
The vulcanising process forms a permanent chemical
bond between the new tread and the original tyre
structure, this involves heating the tyre whilst
under pressure.
After a stringent final inspection and inflation,
the retreaded tyre is ready to return to the road.
|
|
| Vacuum Shearography Inspection |
 In the RINGTREAD production
philosophy, operator expertise is irreplaceable and,
along with specific operating machines, makes it possible
to determine whether or not a casing can be retreaded.
The ITT inspection machines use the vacuum shearography
technique to reproduce the image of the deformations
at a microscopic level. By modifying the tyre's load
conditions and overlapping images, the machine can detect
"bubbles" that indicate separations. This
technique is much more precise, faster and more reliable
than the methods used today: this makes it possible
to create a retread with the best performances, safety
and service life.
|
Quality
Control & Documentation. |
 Through out the process, production
information is gathered via our in house computerised
job card system introduced in 1989.
Details of tyres collect for retreading are recorded
to ensure customers are returned retreads on their
own casings as requested.
This has been a brief outline as to the manufacture
of truck tyre retreads using the pre-cured retread
process. If you have any queries on any aspect
of our process please feel free to contact
us.
Retreads are manufactured by Adco to the highest
standards and specifications with particular attention
paid to detail. The materials we use in the retreading
process are all of the highest quality, from treads
to repair units.
Adco is ISO 9000 registered and all retreads are
manufactured to European Regulation ECE Regulation
109. |
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