A common cause of tire repair failure is an undetected injury or leak in the tire. The tire repair is almost always blamed for the failure, when in fact it was merely a victim of the undetected injury or leak. Here is an example of what can happen: A tire can pick up a very small nail that causes a leak, or it can have a valve that has developed a leak or even a bead that has developed a leak. Each of these could be slow leaks. As a result, the tire becomes under inflated, or soft. at which point it becomes more susceptible to punctures. The tire can then pick up a nail or other foreign object and begin to rapidly deflate. When the tire arrives in the shop, the repair man will very often see this nail, or its hole, and assume that this is the only injury. The injury is repaired with a repair unit and returned to service.The original slaw leak still exists and the tire will again begin to deflate. As the tire deflates, it begins to flex much more than it should. This causes severe stresses on the bond between the repair unit and the tire liner. This can cause the bond to break down, particularly in the critical first 24 ho urs before vulcanization has completed. Often times, the customer will observe that the tire is low again and return to the shop. Because it's only been a few days since the repair was performed, the repairman might automatically assume there is a problem with the repair unit. The tire is demounted and he sees that the edge of the repair has begun to lift. Immediately, the blame is put on the repair - even if air is not leaking through that part of the tire! To avoid this from occurring at your shop, it is recommended that you implement a "double tank / double check" policy. That is, every time a tire comes in for repair, use a dunk tank (or leak detecting solution) to check every part of the tire, valve and bead for leaks both before and after repairing the injury(ies).
