Some time ago, after parking my car in a shopping plaza, I exited to an unnerving noise: the hiss of escaping air. A piece of road debris had pierced the rear passenger tire, which was steadily deflating.

As irritating as the incident was, it turned out to be an easy fix. The spare tire got me home, and I scheduled a visit to the mechanic to inspect the damage. The shop removed the debris—a fragment of an industrial staple, likely shed from a truck somewhere on the highway—and patched the hole. The puncture was minor enough that a repair was sufficient.

However, other flat tires are a result of more substantial damage. When this kind of puncture occurs, a new tire is required. Trying to drive a vehicle with a faulty repair can easily weaken a tire, increasing the possibility that it will fail and lead to an accident.

The location of the puncture plays a big part in determining whether it is safe to repair a tire. The Car Care Council says it is possible to fix a tire if it is pierced in the tread area. If the puncture occurs on the sidewall or shoulder, the area between the central tread and the sidewall, the tire needs to be replaced.

You may also be more likely to repair an existing tire if you get it repaired quickly. The tire company TireRack says that the sidewall or inner liner can wear down if a tire is driven on extremely low pressure, even if the tire has a "run flat" design.

Punctures can be repaired if the hole is a quarter-inch across or less. Some manufacturers may also say a tire should be repaired no more than twice or prohibit repairs if two punctures are within 16 inches of one another.

More serious damage to a tire, such as gashes or long cuts, cannot be repaired. Even if this damage occurs in a repairable area, it is too expensive for the typical repair. Moreover, this kind of tear in a tire will likely weaken the tire by severing its steel belts.

In some cases, a shop may refuse to repair a tire due to other concerns. The Rubber Manufacturer's Association says mechanics should not fix tires which are down to their treadwear indicators, likely a tread depth of one-sixteenth of an inch. It is also unsafe to fix a tire with an improper repair to a previous puncture.

Though there are options to temporarily repair a flat tire, they should not be considered a permanent solution to the problem. The Tire Industry Association says items such as string plugs will let you seal a puncture and inflate the tire, but they will not address any damage caused to the inner liner or sidewall.

Due to this concern, any tire that has been punctured needs to be inspected both on the inside and the outside. It must be removed from the rim for a thorough examination.

Neither a plug nor a patch is a sufficient repair on its own. A plug can often be applied without removing the tire, but doing so risks the possibility that the tire has hidden damage on the interior and will fail at a future point. A patch applied on the interior of the tire will prevent damage in this area, but air and moisture entering through the exterior puncture will increase the chance of tread separation by causing corrosion of the steel belts.

The best repair solution is a combination of both a plug and a patch. The Rubber Manufacturer's Association says that once the puncture has been located, a plug is inserted in the puncture from the inside. A vulcanizing cement and patch are then added for further protection.

If a new tire is needed, the Motorist Assurance Program recommends getting one that matches the original tire's load and speed ratings. Mixing tires of different ratings on the same vehicle can affect its handling, especially if they are on the same axle.

The manufacturer should offer recommendations on where a new tire should be placed on the vehicle if you are not replacing all four tires. In many cases, they suggest that you should get two new tires and place them on the rear axle.

Checking the condition of your tires frequently can alert you to any trouble. Bulges, punctures, cracks, and other damage should all be addressed promptly.