One tire myth that continues to resurface is based on a fictional regulation stating that punctures in steer tires cannot be repaired and returned to the front axle of a vehicle. The confusion is rooted in a federal motor carrier safety standard that makes “ply repairs” illegal.
While the definition of “ply repair” can be the subject of much debate, I have a letter from the Dept. of Transportation that states puncture repairs in the tread area do not constitute ply repairs and thus are legal. If you would like a copy of the letter, send me an email with your fax number and I will make sure you receive one.
But before you consider changing your policy on repairing steer tires, there are a number of issues that must be addressed. First and foremost, the definition of a puncture, or nail hole, repair is an injury that is 3/8-inch in diameter and located in the crown area of the tread. The crown area is the center of the tread that extends 1 to 1.5 inches from both shoulders. Any injury that is located in the shoulder or exceeds the maximum size is defined as a section repair, or ply repair, and therefore cannot be repaired and returned to the steer axle.
Besides the size and location of the injury, another important point that must be made is what constitutes a proper puncture repair. Two types of repairs that are not considered acceptable are the plug-only and patch-only methods. The plug-only repair involves a piece of string or rubber that is forced into the injury from the outside. These on-the-wheel repairs are not only unsafe, but they also increase the likelihood of a non-retreadable casing. The patch-only repair involves removing the tire from the rim so the interior can be thoroughly inspected, but the failure to fill the injury allows water and moisture to enter the belt package and will eventually destroy the casing.
A proper nail hole repair involves three basic principles: remove the damage, fill the injury, and seal the inner-liner. Removing the damage requires a special carbide cutter that trims the belt package and body cords back to solid rubber and stabilizes the area. The injury is then filled with a rubber stem that seals it from the outside. Sealing the inner-liner is accomplished with a repair unit that is vulcanized to the interior of the tire. Puncture repairs not based on these principles cannot be considered consistent with recommended industry guidelines.
Finally, companies that repair steer tires and return them to the front axle must recognize that any tire operated in an underinflated or overloaded condition runs an increased risk of casing fatigue — and steer tires do not have a dual mate to help share the load. The level of fatigue depends on the length of time the tire is exposed to excessive flexing and heat. Since it's impossible to determine the internal condition of a tire in the field with a standard visual inspection, technicians must rely solely on their experience when determining the serviceability of a tire in need of repair.
For some fleets, the risks associated with repairing steer tires and returning them to the front axle are not worth saving a few dollars. But it's important to note that the decision is ultimately based on policy, not federal regulations. So fleets that are primarily restricted to local use with limited highway activity may be needlessly removing steer tires from service simply because they believe, or have been led to believe, that a puncture repair is illegal.