Most people discover that their in-service tire may have a puncture after noticing that their tire is flat or low on air.
There are three common ways to repair a punctured tire: A plug-only, a patch-only repair or a combination repair. The patch-only and combination repairs require the technician to demount the tire from the rim to examine the inside of the tire for damage and repair it from the inside. The plug-only repair does not. When tire rubber has been punctured, the hole tends to close up when the puncturing item us removed. Therefore, unless there has been damage or the puncturing object is still protruding from the tire, it can be difficult to locate the puncture through a visual examination only.
Technicians will often swab the tire with soapy water or dunk it into a tank to look for bubbles of escaping air. It is impossible to inspect the cavity of the tire for any puncture damage without removing the tire from the rim. This is one of the multitudes of reasons why a plug-only repair is an unsafe method.
A plug-only repair is accomplished by inserting the plug through the outside of the tire with an insertion tool. The insertion tool is the removed, leaving the plug in the hole, and thereby filling it. Often times, this plug-only repair is a “string plug,” which consists of a 4 to 5 inch long woven cord that is covered with a tacky substance. String plugs are typically supplied as part of a repair kit consisting of a reaming tool, an insertion tool and a few string plugs. Some kits also contain rubber cement to help create a seal between the string plug and tire. Tires that have been punctured and repaired with a string plug may hold air for months, years even for the remaining life of the tire. For this reason, many consumers consider a string plug repair a permanent solution. The tire manufacturing industry expressly disagrees. Various industry publications state that the greatest potential danger caused by a string plug repair is that this type of repair allows air and moisture to penetrate the body of the tire. The tire industry maintains that these elements seep in between the layers of the tire allowing the steel belts to degrade and causing the tire to deteriorate and corrode from within. Over time, this corrosion weakens the steel belts and the bonds between the rubber-to-rubber layers and rubber-to-the-wire layers of the tire, greatly increasing the risk of a tread separation. An additional risk of performing a string plug repair is that a puncture, even if it is within the “repairable” area of the tire, may cause damage to the inside of the tires. Without inspecting the inside of the tire, it is impossible to determine whether any damage has occurred, requiring it to be scrapped.
