Rim tape protects the tube from the rim. If it fails to do this you'll get a puncture.
The rim tape does different jobs depending on the construction of the rim and can fail in a number of ways; spoke Heads – Some rims are made of a simple strip of metal. The rim tape protects the tube from the ends of the spokes. Tightening the spokes may push their heads through the rim tape. If this happens remove the tape and file the spokes down.
Spoke Holes – Some rims have a tubular section. The rim tape protects the tube from the holes in the bed of the rim well. The holes are necessary to connect the spokes to the nipples when building a wheel. If the holes aren’t covered the tube will blister into them and then puncture.
The rim tape may be a rubber or plastic strip. This may fail at the thin sections around the valve hole. When you select new tape make sure you replace it with a purpose-made strip of adhesive fabric of the correct width for the rim. It needs to cover the holes for the spoke heads but not wide enough to interfere with the tyre.
Remove The Rim Tape
Remove the old rim tape if it has failed.
Replace The Rim Tape
Replace with a strip of purpose made adhesive fabric. If you don’t have a purpose-made fabric rim tape two or three rounds of electrical tape will do the job. Use a bradawl to re-open the valve hole pushing from the inside out.
If your tyres are a very tight fit use electrical tape instead of fabric rim tape to give a little more room when it comes to fitting the tyre.