How to Plug a Tire: Step-by-Step and When Not to Use a Plug

01When You Can (and Cannot) Plug a Tire

A plug is safe only for punctures in the tread area, the center three-quarters of the tire width. The hole also has to be no bigger than about 1/4 inch (6mm) across. A nail inside that zone is a candidate for a plug or a plug-patch repair.

Do not attempt a plug if: the puncture is in the sidewall or shoulder (the curved transition from tread to sidewall); the hole is larger than 1/4 inch; there are multiple punctures close together; the tire is run-flat and was driven on while flat; or the tread depth is at or below the wear indicators.

Sidewall punctures cannot be repaired, period. The sidewall flexes with every rotation, and any seal there works loose under that constant flexing. A sidewall-punctured tire gets replaced.

02What You Need

Tire plug kit: includes a T-handle reamer (to clean and size the hole), a T-handle insertion tool, and string plugs (worm-like strips of rubber-impregnated cord). These kits are available at any auto parts store for $5 to $15.

Compressed air: a portable tire inflator or the air hose at a gas station to re-inflate the tire after plugging.

Pliers: to grip and remove the object after you are ready to plug.

Soapy water in a spray bottle: to locate the puncture if it is not obvious, and to verify the seal after plugging.

03Step-by-Step Tire Plug Procedure

Step 1: locate the puncture. Spray soapy water across the tread and watch for bubbles rising around the hole or the embedded object. If you can see the object, confirm it sits in the tread area, not the shoulder or sidewall.

Step 2: leave the object in place until you are ready. While it is stuck in there, it is partly sealing the hole. Pull it only right before you plug.

Step 3: ream the hole. Pull the object with pliers, then run the reamer tool in and out to clean, round, and slightly widen the channel. That gives the plug a fresh surface to bond to.

Step 4: thread the plug. Fold a string plug in half and feed it through the eye of the insertion tool, leaving equal lengths hanging off each side.

Step 5: insert the plug. Push the tool firmly into the hole until about an inch of plug is left above the tread, then pull it straight back out in one firm motion. That seats the plug and releases it from the tool.

Step 6: trim the excess. Cut the plug flush with the tread, or just proud of it, using a knife or scissors.

Step 7: inflate and test. Air the tire up to the correct pressure from the door-jamb sticker, then spray soapy water over the plug and watch for bubbles. If any show up, the plug did not seat. Pull it and redo the insertion.

Note: a string plug alone is a temporary repair. The recommended permanent repair is a plug-patch combination applied from inside the tire, which requires demounting. Have a tire shop perform a permanent repair as soon as practical.

04Plug vs Patch vs Plug-Patch

A string plug alone (external repair) is a widely-used roadside fix, but tire industry standards consider it temporary. Some tire manufacturers void warranties on plugged tires.

An internal patch seals the inner liner but does not fill the puncture channel through the carcass, so most standards call it temporary too.

A plug-patch combination, where the plug fills the channel and a patch seals the inner liner from inside, is the industry-standard permanent repair. The U.S. Tire Manufacturers Association treats this as the correct fix. It means demounting the tire, and any shop can do it for $20 to $40.

For a long-distance daily driver or a tire you intend to keep for its remaining tread life, have a permanent plug-patch repair done at a shop rather than relying on a field plug.