There is nothing more frustrating than being told that a simple puncture in the shoulder of a truck tire is unrepairable. After all, the difference between the location of a repairable puncture and one that is non-repairable is often measured in millimeters. For decades, the only puncture repairs that were allowed in the field had to be located in the crown area, which is the center of the tread approximately 1 to 1.5 in. from each edge. Injuries outside the crown area in the shoulder were considered unrepairable in the field, so they had to be referred to a full-service repair facility or a retread plant.
One of the main reasons that standard puncture repair materials were not allowed in the shoulder area was the simple fact that the repair unit itself (or patch) would extend into the sidewall. If the edge of the repair unit or the edge of the reinforcing ply material in the repair unit was located in the high flex area of the sidewall, it’s not a matter of if it will fail but when it will fail. As a result, a significant number of tires were unnecessarily scrapped because the fleet did not want to wait or pay for a full section repair.
The Tread Rubber and Tire Repair Materials Manufacturers Group (TRMG) is an organization that establishes recommended practices for the tire retreading and repairing industries. For the past few years, TRMG has been working on a document that would outline the industry guidelines for a “reinforced shoulder repair,” or RSR. At the recently held Global Tire Expo in Las Vegas, TRMG led a seminar based on the guidelines it approved the previous day—and during that hour in the Las Vegas Convention Center, it was the start of a new era for the truck tire repair industry.
The key to success for the RSR is the positioning of a larger and longer (but more expensive) repair unit. Standard puncture, or nail hole, repair units are the smallest of the repair materials because the primary purpose is to stop the air leak when the injury is in the crown area of the tread. There is very little flexing in that area, so adhesion is not a problem and the need for reinforcement is minimal. Unfortunately, the same materials cannot be used for an RSR.
When a standard low-profile 22.5-in. truck tire travels one mile, it makes about 512 revolutions. This means each sidewall cable flexes 512 times in a mile or 51.2 million times during its first 100,000 mi. That’s a lot of flexing. The longer repair unit in the RSR makes sure the ends of the patch and the reinforcing ply material are anchored in a non-flex area. If the RSR is installed correctly, it will withstand the millions of flexing cycles it will experience during its lifetime.
Commercial truck tire dealers and retreaders finally have a reliable and economical tool to repair small punctures in the shoulder area. For some fleets, the RSR will lower tire costs because the expense/time of a section repair becomes unnecessary. And while the RSR will probably cost a little more than a nail hole or puncture repair, it will keep a lot more tires in service and prevent some tire purchases on the road. Injuries in the sidewall and those larger than industry recommendations will remain section repairs so nothing changes in that regard. But the simple puncture in the shoulder can now be safely repaired in the field, and that’s great news for everyone in the tire and transportation industries.
Kevin Rohlwing can be reached at [email protected]
