Repairing a tire properly requires it be demounted from the rim so it can be inspected on the outside and inside, remove damaged material, fill the void with rubber and seal the innerliner with a repair unit.
Puncture repairs are limited to the center of the tread area. If there are punctures or damage in the shoulder or sidewall of the tire, it is not repairable.
Many times, a simple object, such as a nail in the tread, can severely damage the sidewall and may not be seen on the outside of the tire. Therefore, on-the-wheel wheel repairs such as string plugs are not recommended and must be considered temporary.
In fact, a plug by itself or a patch by itself is not an acceptable tire repair because the plug does not seal the innerliner permanently and the patch does not fill the void created by the piercing object.
Without a secure seal to repair the injury, water can enter the body of the tire and start corroding the steel belts. Emergency tire sealant aerosols are not recommended as long-term solutions to a flat tire for the same reasons.
Once the tire is off the wheel, here are the general steps involved in applying repair material:
- Remove the puncturing object, noting the angle of penetration. Using a blunt awl, inspect the wound and the direction of the injury angle. Remove any loose foreign material. If the wound was made at greater than a 25-degree angle, use a two-piece repair system. And if the sidewall is damaged or if the wound is close to it, do not repair.
- Prepare the surface by cleaning the area around the puncture thoroughly with an appropriate (pre-buff) innerliner cleaner. Use a clean cloth and/or scraper, according to the repair material manufacturer’s recommendations to remove dirt, mold, lubricants or anything else that could compromise repair unit adhesion or contaminate buffing tools.
- The next step is to prepare the injury channel for its repair. Using a powered drill (1,200 rpm max.) with an appropriately sized carbide cutter, start at the inside of the tire and ream the puncture channel several times. Then repeat this from the outside. Use a probe to double-check any splits in the radial plies surrounding the injury and remove any additional damage found.
- Select the correct size and type of repair patch based on the repair materials manufacturers recommendations. Center the patch over the wound and using a tire crayon, outline an area a half-inch larger than the material.
- To prevent contamination and preserve the outline, buff within the marked area thoroughly and evenly with a low speed buffer (5,000 rpm max.) with a fine wire brush or gritted rasp. Take care not to expose or damage tire casing body (ply) cords. Buff to a velvety surface.
- Remove all rubber dust from the buffed area by using a fine wire brush and vacuum, being careful to avoid touching and contaminating the area. Do not use compressed air as air lines contain contaminants such as oil and moisture, which would reduce adhesion. Follow the repair material manufacturer's recommendations for cleaning the buffed area.
- The tire must be “relaxed” when the repair is applied, meaning the beads are not spread excessively. Apply the patch, following the instructions based on a one- or two-piece repair unit. Allow any chemical cement to dry according to the repair material manufacturer's procedures. Do not use forced air or outside heat source to accelerate drying time.
- Remove the protective layer and inspect the repair.
It’s important to be aware that tires that contain puncture sealant(s) may have been damaged as a result of being run under inflated and/or overloaded. Be sure to inspect these accordingly before repairing tire. Before repairing tires that were manufactured with a puncture sealant, contact the tire maker or sealant manufacturer for repair recommendations.