subject: How to Find the tire puncture? [print this page] How to Find the tire puncture? How to Find the tire puncture?
You'll need to do a little detective work to find the puncture. To track down the source of the problem, follow these steps:
Examine the inner tube by listening for a leak. If it doesn't have air, pump it up to a larger shape than round. With the additional air pressure, the leak may make a hissing sound as the air tries to escape.
If you're having trouble listening for the leak, float your finger above the surface of the inner tube until you feel the flow of air escaping. If you've narrowed the source of the leak to a small area, but you still can't find the actual hole, apply a small amount of saliva to the tube. Bubbles will lead you to the source. If you don't want to gross out your riding partners by spitting on your tube, you can sometimes find a very small hole or slow leak by holding the tube near your lips. The lips are very sensitive and should feel the smallest amounts of air leaking out.
If you're still having trouble finding the leak, submerge the tube under water. A stream of bubbles will be clearly evident after submerging the tube. When you remove the tube from the water, wrap it around your finger at the source of the leak or mark it so that you don't lose the location.
In some cases, a hard-to-find leak may be traced to a valve problem. This is one situation in which you may want to employ the saliva technique. Apply a few drops of saliva to the end of the valve to look for signs of air escaping. For a Schrader valve, you can try tightening the valve core. If this doesn't work, you may need to remove the core, put a few drops of oil on the spring, and reinstall the core. This technique requires a valve cap with a built-in valve core tool or a separate valve core tool, something you can buy at bike shop. If the leak is coming from a cracked or cut stem, you'll have to replace the tube. In the case of Presta valves, more likely than a leak is the valve breaking (because valves are fragile).
Valve leaks are hard to find when the tube is outside the tire because the tube usually has very little air pressure and leaks in the valve usually only show up when there is a lot of air pressure (that is, when the tube is sitting inside the tire and the tire is inflated to the proper air pressure).
