How To: Patch a flat tube

Don't toss those popped tubes! Patch 'em! A good patch becomes the strongest part of the tube. In fact, you can patch a tube many times and keep right on using it. Knowing how to patch comes in handy, too, when you're on a ride and discover that your spare tube has a hole in it. 

You'll need a patch kit, pen, pump and, of course, your punctured tube!

Find the hole:

Inflate the tube listening for a hissing sound and follow it to find the hole. If you can't hear a hiss, hold the tube next to your face (or lips; they're especially sensitive) as you search for the hole, and you should feel the escaping air. If you can't find the hole, try adding more air. Still no luck? It's probably a really slow leak. To find it, submerge the tube in water and look for bubbles. Can't inflate the tube? There's probably a hole in it so large that the air leaks out immediately. Look for it or have a friend listen and look while you pump.

Tip: If the tube has a tear 1/2-inch long or longer, has several holes in it or has a hole next to the valve, it'll be difficult to impossible to patch. Time to buy a new tube. Use the old one to make a water-balloon slingshot.

Mark the hole: 

Use the little chalk piece in the patch kit (if it came with one) or a pen to mark the hole so you don't lose track of it. But, don't mark the actual hole because the glue may hide the marks, which means you might lose track of the hole. To prevent this, place marks on either side of the hole about an inch away. Alternatively, simply tear the hole slightly larger (about 1/4 inch in diameter). Don't worry, the patch will make the tube good as new.

Tip: Be gentle when marking the tube by tearing, especially on lightweight tubes, which are fragile.

Sand the tube: 

Prepare the tube for the glue and patch by roughing it up at the hole with the sandpaper. Scuff a spot larger than the size of the patch and brush off the dust with the back of your hand.

Tip: You can also blow the dust off the tube but your breath is moist and you don't want to wet the tube. So blow carefully.

Apply the glue: 

Unscrew the glue tube, invert the cap and press it onto the tube to puncture and open the glue (the cap has a spike in its end). Squeeze a blob of glue onto the hole and spread it with the end of the tube to cover the sanded area. Be sure to make a glue spot slightly larger diameter than your patch. Now wait at least 5 minutes for the glue to dry fully (it'll look cloudy when dry).

Tip: It may seem counterintuitive, but the glue must be dry before applying the patch. You can wait as long as you want -- even weeks As long as the dried glue remains clean and free of dust and dirt, the patch will stick to the tube perfectly when you get around to applying it..

Patch the tube:

The last step is sticking on the patch. Hold it by the cellophane and peel the foil off to expose the patch's sticky side. If the foil won't lift, try pulling from a different edge. Now, press the patch on the tube making sure the hole is in the center of the patch. To finish the job, roll your pump end over the patch to fully seat it. Don't remove the cellophane as it keeps the patch/glue from sticking to the tire. Good job. You've recycled your tube!

Tip: To ensure that the repaired tube won't let you down, it's best to give it a final check by inflating and listening for leaks or submerging the tube and looking for bubbles. If you find another hole, patch it, too!

About "glueless" patches: 

Some cyclists prefer to carry "glueless" patches for on-the-trail repairs. These come without a tube of glue, so applying it and waiting for it to dry are unnecessary. Instead, the patches carry a strong adhesive. To fix a puncture, buff the tube lightly with the sandpaper included in the kit, brush off the dust, peel off its backing and affix the patch. Careful! Don't trap any air beneath it.

Tip: A glueless patch doesn't become a permanent part of the tube the way glued patches do. So glueless ones work best as temporary repairs. It'll get you home, but you may find that the tube slowly leaks air. No problem. Simply replace it with a new tube before your next ride.