Tire Repair: Plugging vs. Patching

Flat tire
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You're driving along the highway when suddenly you feel the car lurch and then hear the telltale thunk thunk thunk of a flat tire. You get out, change it, and then head off to get it repaired. But which method is best for fixing a flat tire, the plug or the patch?

The debate about the proper way to make these repairs has gone on for decades. Some experts believe that patching is too time-consuming and complex a procedure for something like a small nail hole, in which case a plug will do just fine. Others assert that plugs are dangerous no matter what, and patches are the only proper way to fix a tire. In 2012, the New York State Legislature even went so far as to introduce legislation making it illegal for repair shops to use plugs or patches on their own—they must be used together. Needless to say, the bill did not pass. Here is our take on the subject:

How Plugs Work

Tire plugs are made of short strips of leather covered with a gooey, unvulcanized rubber compound. When forced into a nail hole, the plug fills the hole and the rubber goo vulcanizes under the heat of driving to fully seal the repair. Plug repairs can be made very easily and do not require the tire to be taken off the wheel to repair, although those who claim that repairs can be made with the wheel still on the car have clearly never tried to do so themselves. 

Plug Pros and Cons

The advantages of plugs include low cost and simplicity, and most repairmen will tell you that the vast majority of plugs will last for the life of the tire. You can even plug your tire yourself the old-fashioned way, or buy a special tool that revolutionizes the process for the do-it-yourselfer.

On the other hand, it is clearly possible for a plug to fail, and that's never a good thing. However, most plug failures occur because the hole is too large for the plug or is otherwise irregularly shaped, in which case the damage should have been patched in the first place.

How Patches Work

A patch is an adhesive-backed piece of rubber that is placed on the inside of the tire. The adhesive then vulcanizes when the tire heats up. This is a much stronger and more effective repair. Because patch repairs are generally the province of trained technicians who have the equipment to dismount and remount the tire, they take longer and cost more. On the one hand, this can be a form of overkill for very small nail holes that could as easily be plugged. On the other hand, when it comes to tire safety, overkill cannot easily be described as a bad thing.

When to Replace and Not Repair

Keep in mind that neither a plug nor a patch should ever be used to repair damage that is located within an inch of either sidewall. The sidewall and shoulder areas of the tire will flex too much when rolling and will eventually work any repair loose, often causing an unexpected and catastrophic loss of air while driving.

Another thing to keep in mind is that if the tire has been run on while flat or at low pressure for more than a couple hundred yards, there is a strong likelihood that the sidewalls have been damaged. When a tire begins losing air, the sidewalls begin to collapse. At some point, the collapsing sidewalls will fold over and begin to rub against themselves. This process will scrub the rubber liner off the inside of the sidewalls until the sidewall is damaged beyond repair. If you can see a “stripe” of wear circling around the sidewall of the tire that is softer to the touch than the rest of the sidewall, or if you remove the tire and find large quantities of “rubber dust” inside, or if the sidewall has been worn away until you can see the inner structure—do not repair or put air pressure into the tire, as it is highly dangerous. Just go ahead and buy a new tire instead.