The steps to patching a tube outlined below assume that you’ve already removed the tube from the tire. If you haven’t done that yet, here are directions
If you are cost-conscious, patching your tubes and using them again may be an option to try and save some bucks, but be forewarned: a patched tube will never be as reliable as a new one. The patch can fail again, so to be on the safe side, a patched tube should probably be replaced with a new one as soon as you get the chance.
- Locate the puncture
Inflate the tube so that you can find the source of the leak. You can sometimes find the leak by listening for the hissing and following the sound to the hole. A more reliable way is to fill a sink with a couple of inches of water, and then placing a portion of the inflated tube underneath the water, rotating the tire until you’ve watched the entire tube go through. The leak will give itself away by the bubbles it produces when its section of the tube goes underwater.
This is an important step. If you cannot find the leak, you will not be able to repair it.
- Prep the site
Using sandpaper, roughen the area of the tube that is slightly larger than the patch you will use. This allows the rubber cement to adhere to the tube.
- Apply rubber cement
Apply a thin layer of rubber cement at the site of the leak over the area you just sanded. Again, this should be slightly larger than the patch you will use. It is not important if you apply rubber cement directly on the hole or not. Allow the rubber cement to dry, a process that should just take a minute. The rubber cement should go from clear to cloudy as this happens. You can hasten this step by blowing on the glue.
- Apply the patch
Most of the time, the patches that come in a pre-made kit will have a thin foil backing which you will need to remove to expose the adhesive. Take that backing off, and apply the patch directly over the hole, pressing it firmly down to seal it onto the rubber cement.
- Inflate the tube
To inflate the tube, place it into its tire and put the tire back onto the rim. Steps to do that are here. Inflating it on the rim and in the tire will help seal the rubber cement bond even more thoroughly as it helps press the patch down onto and into the rubber cement to give even more security that it will hold.
- Even when you think you’ve found the leak, be sure to still check the entire tube, as there may be more than one puncture.
- A piece of chalk comes in handy for marking the leak’s location. You can circle the spot or mark it with an X. Otherwise they are easy to lose.
- Leaks that occur at the base of a valve stem or along the seam of the tube are usually impossible to repair.
- If you are out on the road, you can find the leak by dipping your tube in a creek or puddle. If no other water is available, moisten your fingers with saliva and rub lightly over the surface of the tube until the source of the suspected leak is located.
- If you do not have a patch, you can try using a piece of another old inner tube cut to the right size if you are really desperate. You will need to use sandpaper to roughen it, since it will not have the same adhesive as the patch from a store-bought kit. It is more difficult to get these patches made from inner tubes to stick and hold, but it will usually be enough to get you home.
An inexpensive store-bought patch kit usually includes everything you need. They generally cost only three or four bucks, and I strongly encourage you to carry one of these with you whenever you are on your bike.
What You Need
- Rubber Cement
- A Small Piece of Sand Paper