Basic Bicycle Maintenance
Fixing a Flat
This wikihow lays out the steps in changing an inner tube:
There are dozens of little mistakes you can make installing a tube that will cause another flat; if you bring the flat to a bike shop the mechanic will know how to best install a tube. Either way, you should always diagnose the cause of the flat and choose the proper remedy. If you bring your bike to a shop, make sure to find out the cause of the flat; many bike shops will not do this because its easier to just pull out and replace the inner tube. Here are six common problems listed below:
1.) Exterior Puncture (most common)
Evidence: Hole is on the outside (pavement side) of the tube.
Cause: Something sharp on the road pierced your tire and inner tube.
Remedy: Replace or patch the tube - usually the hole in the tire is not big enough to warrant replacing. If the hole is big enough, replace the tire. Having a pinhole in the tire is OK, pressure will close the hole, and the tube will not push through. If you can't replace the tire, you can put a square inch of gapher tape or a dollar bill on the inside of the tire as a temporary emergency solution.
Evidence: Hole is on the inner (rim) side of the tube.
Cause: The tip of a spoke poked through your tube, or there was a gap where your rim tape wasn't covering a spoke hole.
Remedy: Replace the tube and make sure to cover up the gap or sharp point. Adhesive-backed cloth is the best material for rim tape.
3.) Pinch Flat (you didn't fill your tires up enough!)
Evidence: Snake bite! A double puncture, two small parallel slits mimicking snake teeth.
Cause: Tire pressure was not high enough, or tube not properly installed, the tire pinched the tube against itself or the rim.
Remedy: Check that the pinch flat did not rip the tire as well. Replace the tube and make sure to inflate to recommended PSI located on the side wall of the tire. Be aware that older, low quality rims may not handle the max pressure advertised on the tire.
4.) Tire Seating
Evidence: Your tire exploded violently but there is no damage to the tire.
Cause: Tire was not seated properly on the rim, inner tube came out between rim and tire.
Remedy: Double check that there are no rips or holes in the tire. Replace the tube, inflate slowly and make sure the tire is seated properly all the way around (not bulging, the tire line is even all the way around the rim).
Evidence: Air leaks out the valve or valve stem.
Cause: A damaged valve.
Remedy: Replace the tube, make sure the valve is straight.
6.) Unidentified Slow Leak
Evidence: Can't find any leak.
Cause: A tiny, tiny little hole somewhere.
Remedy: Double check the rim / tape and tire. Overfill the tube as much as you can to try to find the hole. Replace the tube.
Chain Cleaning + Lubrication
Ideally your chain should be clean and lubricated. This wikiHow is very thorough, not all steps are necessary:
We recommend lubing at least once a month, or after riding through wet/dirty conditions, and going through all gears before wiping the excess off.