Performing Performance Repairs

Road hazards are a daily danger for all types of tires regardless of their speed rating, design or what kind of vehicle they’re mounted on. Nails, screws, rivets, pieces of wire, broken glass, shards of metal, sharp stones and anything else that ends up as debris on a road surface may, under the right circumstances, penetrate and puncture a tire. And once a tire has been punctured, it usually begins to lose air. Sooner or later it will go flat and have to be repaired or replaced.
The question is, what kind of repairs are considered acceptable by the tire manufacturers, and how do repairs affect a performance tire’s speed rating and safety?
The answer to these questions depends on several things:
1. Whether or not the tire suffered any structural damage as a result of going flat. No tire should ever be repaired without completely removing it from the rim for a thorough visual inspection inside and out. What may seem like nothing more than a simple nail hole may be more serious if the tire was driven on after it went flat. If the tire shows any sign of run-soft or run-flat damage such as burned, blued or blistered rubber inside, or cracks, breaks or separation in the innerliner, replacement is the only acceptable option.
2. The size and location of the damage. As a general rule, most tire manufacturers allow repairs of holes up to 1/4-inch in diameter in the tread area. Larger holes, cuts or multiple punctures require replacing the tire. Some tire manufacturers also allow small holes in the shoulder area and sidewall to be repaired, provided the holes are no larger than 1/8-inch in size. Others, however, do not want their dealers making any sidewall repairs because of the flexing that occurs in this area.
3. The speed rating of the tire. For speed ratings of Q through T, repairs that follow the above guidelines are generally allowed. But for tires with H and higher speed ratings, the answer isn’t so simple and varies from one tire manufacturer to another, as well as from one brand of tire to another.

Voiding the Rating

Bill VandeWater, consumer products sales engineering manager at Bridgestone/Firestone (BFS) said any tire (including speed-rated units) can be repaired provided the repair conforms to the above guidelines. But he also says BFS does not allow any sidewall repairs. And, if a tire is rated H, V or Z, the speed rating no longer applies after a repair.
“Though some people claim they can successfully repair sidewall punctures, we think it’s too risky. If a tire has shoulder or sidewall damage, we don’t consider it to be repairable. The tire must be replaced.”
VandeWater said if a speed-rated tire is repairable (the hole is in the tread only, is smaller than 1/4-inch in size, and the tire shows no signs of internal damage), the customer needs to be advised that the speed rating no longer applies after repairs have been made.
“We don’t want people driving 150 mph on a patched tire,” said VandeWater.
Also, repairs must be made using a plug to fill the hole with a patch over it on the inside to seal the liner (or a combination patch/plug if the angle of the hole is 25Þ or less).
The hole has to be plugged to prevent moisture from penetrating the tread from the outside. Moisture that enters a hole can rust the steel cords inside the tire, weakening the tire and increasing the risk of ply separation and tire failure. Likewise, a patch inside is necessary to stop moisture inside the tire from penetrating the damaged area, too.
Goodyear’s repair philosophy is similar to that of Bridgestone/-Firestone in that Goodyear does not allow sidewall repairs. If a tire has a puncture anywhere between the tread edge and bead, the tire is not repairable and must be replaced. But as long as a tire conforms to the repair guidelines and is repaired using a plug/patch combination, Goodyear said it does not affect the original speed rating of the tire as long as the number of repairs does not exceed one.

Follow Recommendations

Mike Wischhusen, director of product marketing at Michelin, said tire dealers should always follow the tire manufacturer’s specific recommendations when repairing a tire because they can vary according to the brand on the tire.
“For Michelin brand tires that have speed ratings of Q through T, we allow repairs to be made on holes up to 1/4-inch in the tread and up to 1/8-inch in the sidewall. But on tires that have speed ratings of H or higher, we allow no sidewall repairs. In both cases, the repair does not affect the speed rating of the tire.
“For our BF Goodrich and Uniroyal brands, we allow no sidewall repairs in tires speed-rated T or below, and no repairs of any kind in the tread or sidewall in tires speed-rated H and above,” said Wischhusen.
Because of the liability risks associated with tire repairs today (especially on speed rated tires), dealers would be well-advised to make sure all employees who service tires are familiar with the repair recommendations and procedures for every brand of tire they service. The general repair provisions put forth by the Rubber Manufacturer’s Association – or the specific guidelines of the repair product maker ®“ are fine for most applications, but in the case of speed-rated tires it’s important to find out what the tire manufacturer recommends before any repairs are made.