Tube patching

I've had an on-again-off-again relationship with bicycle inner tube patching going back nearly five years. The cycle goes as follows: for months I patch punctured tubes with the hope of saving money; then for months I curse at leaky patches and toss tubes after new flats. Leaky patches are the worst—a failed patch is a single flat twice repaired.

Are patches worth it? Can they be made to work reliably? I've reentered the on-again phase and after successfully patching seven straight tubes, I think this time it's the real thing and patches are worth it. What changed is that I discovered I was previously doing it wrongly.

There exist numerous how-to guides on the Web for patching tubes, and they all say the same things, so I'm not going to further that redundancy. But I know I can read every word in a short how-to and still screw it up, so I'm going to describe some between-the-lines wisdom I've gleaned from experience—including what I was doing wrongly.

• Keep some air in the tube while patching. I aim to have the tube be the same size as it will be when inflated inside the tire. The reason for this is that patches don't stretch, and patching an uninflated tube creates a cinch spot that won't evenly expand to the shape of the tire.

• The step of sandpapering the tube before applying the rubber cement is critical. This is because you're not just “roughening up” the tube surface; instead, you're removing the non-stick layer put there to prevent the tube from sticking to its mold during manufacturing. That non-stick layer serves no purpose after manufacturing, so sandpaper thoroughly.

• As for what I had been doing wrongly in previous years, that has to do with using a small amount of rubber cement, not a big amount. This has to do with a counterintuitive property of rubber cement, which is that it must be completely dry for it to adhere—unlike glue, which must be wet. I now use my fingertip to smear a layer of rubber cement thin enough so that it dries within seconds. If it doesn't dry within seconds, I've used too much.

• Keep in mind you needn't entirely remove the tube from the tire to patch. If you know where the leak is, such as when you hear the “hiss” of a fast leak, you can remove only the leaky part of the tube, thus keeping the wheel on the bike. This is the fastest way to fix a flat other than a wheel change.