By The Tire Industry Association
How many times have you seen the sign that reads “Flats Fixed” and wondered what it really meant?
There’s usually a dollar figure directly associated with those words and it’s typically a lot less than other places in the area.
If you’re brave enough to let a “Flats Fixed” place gamble with your life, your vehicle and your cargo, you’ll definitely save a lot of money over the long haul if your luck holds out. After all, that’s what it comes down to when flats get fixed for 10 bucks. If you’re lucky, the fixed flat won’t come back to haunt you.
Most flats are fixed from the outside while the tire is still mounted on the rim. The penetrating object is removed and the void is filled by one or more rubber plugs that are inserted until the hole no longer leaks air.
Simply cut away the excess rubber on the outside and you’re flat is fixed.
Of course, nobody can see if the object caused additional damage on the inside of the tire, so you just have to take that chance.
Then there’s the fact that none of the tire manufacturers actually recommend an on-the-wheel fix. Any tire failure that results from a plugged tire is sure to become the subject of major litigation.
As far as the truck tire industry is concerned, there is only one way to repair a tire, and it includes several steps, in addition to a number of restrictions.
Perhaps the most important is the size and location of the injury. Puncture repairs that can be performed in the field are only allowed in the crown area of the tire, which is the center of the tread approximately 1- to 1.5-inches in from each shoulder.
Injuries outside the crown area may be eligible for a section repair that is typically installed at a retread plant. The maximum size of a puncture repair is 3/8 ths of an inch and there is no established maximum number of repairs - as long as the repair units (or “patches”) do not overlap and the same radial cable is not injured more than once.
It’s also important to note that tires with a puncture repair can be installed on the steer axle, while those with a section repair cannot.
Many companies and drivers choose not to repair steer tires and return them to the front of the vehicle, but it is not illegal to do so.
Each of the steps in a tire repair has a specific purpose:
- Cleaning the innerliner prior to any work removes contaminates that will reduce the amount of adhesion between the repair unit and the tire.
- Removing the damaged body cables and steel belts stabilizes the area around the injury which prevents a separation down the road.
- Filling the injury with a cured rubber stem prevents water from entering the tire body.
- The combination of the vulcanizing cement and cushion gum molecularly bonds the stem to the tire so it becomes part of the casing.
- A smoothly buffed innerliner assures the repair unit creates a final seal on the inside of the tire after it is vulcanized in the same way as the stem.
From a structural standpoint, a properly repaired tire is restored to its original condition.
Even though both approaches to resolving a flat tire achieve the same goal of stopping the leak, there are distinct differences that can have lethal consequences. Besides the damage on the inside that cannot be seen when plugs are installed with the tire still mounted on the rim, there is also the possibility of missing the hole on the inside of the tire so additional damage is created.
Once again, the technician can jam enough plugs in the hole to stop the leak, but eventually the broken cables will result in a separation.
Likewise, if the repair method involves the wrong size carbide cutter for removing the damage in the injury channel or the cutter needs to be replaced, a separation can result.
Each belt package is made up of steel cables which are smaller wires that are twisted for additional strength and uniformity. When a cable is broken, it starts to unwind as the tire flexes in service.