BRIDGESTONE | SIDECUT REPAIR
WHAT IS THE DIFFERENCE BETWEEN 1-STEP AND 2-STEP REPAIRS? A 1-step repair means that after preparation by completely fi lling the damaged area and applying the patch, the tyre is cured under heat and pressure, resulting in hot vulcanisation of the damage and the patch in one step. In a 2-step repair, the damage is fi lled and
cured with the help of a smaller vulcanising equipment (e.g. TP-II) in a fi rst step, and after this process the inner liner is buffed and the patch bonded to the tyre by a cold application process with chemical curing in a second step.
WHAT DAMAGE SIZES ARE REPAIRABLE? The repairable size of the damage varies very much depending on the dimension of the tyre. Therefore a repair chart is needed to fi nd the maximum size for the tyre in question. Here are two examples: - A smaller truck tyre with a width of 8.25” or 225mm and a 100 to 90% ratio can accept a repaired damage size of a maximum of 20mm x 130mm or 40 x 80mm in the sidewall. (The smaller damage size is related to the number of radial cords damaged = axial direction; the bigger number is related to the length of the damage from the shoulder to the bead = radial direction). - A bigger truck tyre with a width of 425mm and a 65% ratio can accept a damage size of a maximum of 30 x 140mm or 45 x 100mm in the sidewall. The repair charts are to be found inside the
boxes of patches. They are continually updated and the workers concerned can read these correctly after repair training.
WHY THERE ARE SO MANY DIFFERENT PATCH SIZES? Due to the many different dimensions of tyres in the market, with high and short sidewalls or ratios from 100% to 30%, we need repair patches for all type of damage and sizes. As a patch supplier, REMA TIP TOP GmbH attempts to reduce the number of different patches by replacing some dimensions by new sizes which can cover the spectrum of two patches from the old program (e.g. RAD116 replaces RAD112 and RAD114 for car tyres, and RAD135new replaces RAD135 and RAD145 for truck tyre tread damage).
HOW DOES VULCANISATION TAKE PLACE? Vulcanisation is a chemical process that causes single molecules in the raw rubber material to build chains of molecules which can stabilise their position in the material by building bridges between them with the help of sulfur and accelerators. You can feel the difference by
Not repairable
Pressure & Time. The necessary chemical substances are already included in the materials supplied by the provider. So please never say “glue” when referring to a vulcanising fl uid. Glue is completely different from vulcanising fl uid.
Section repair required
MINICOMBI
pulling a piece of raw rubber material with your own hands. It becomes longer and will stay that length after you release it. That means it can be deformed and it is sticky; you can form it into a ball. If you take a piece of vulcanised rubber into your hands, however, you may be able to pull it and elongate it, but it will go back to its old shape after you release it. For perfect vulcanisation there are three important factors that are needed: Heat &
• Never mix materials from different repair systems or suppliers
ARE THERE ANY INTERNATIONAL STANDARDS TO BE FOLLOWED? There are some standards focusing on the retread industry and the repair process inside this industry. (e.g. ECE-R108 and ECE-R109). In some countries there are local standards and regulations directly relating to tyre repair, for example in the USA, Germany, Austria, the UK and the Netherlands. (TRA, RiLi, etc.) They all try to give a minimum standard for safety reasons. The main items common to these are:
• The tyre must be inspected carefully before the repair process starts. The general state of
the tyre must also be taken into consideration. • • Look for hidden additional damage
Respect national limits and regulations
HOW TO CARRY OUT A 2-STEP REPAIR FOR SIDECUTS IN 6 STAGES: 1. CLEAN
The tyre has to be clean enough for inspection and the inner liner must be cleaned with LIQUID BUFFER and then a vacuum cleaner to remove all traces of silicone, graphite and other mould lubricants.
26 JUNE 2011 real QUESTIONS real ANSWERS
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