Skip to main content

Fix That Flat!

There have been requests for text versions of the fix-a-flat video published below, so here you go!  Feel free to print out.  I'm cribbing this down to key items to print on a 3 x 5 and will have them laminated in the store.  I'll post when that is ready.

I’ve lost count of how many flats I’ve fixed only to have the bit of thorn or glass that got left in the tire puncture the new tube. Be sure to diagnose what caused the flat!  Start by taking the offending wheel out of the bike (I'll post those details next), and then:

  • Dig your tire levers from your tool kit (remember your tool kit?)
  • Using the tire lever, or levers if necessary, remove one side only of the tire from the rim. Remember that if the tire is an especially tight fit you can hook the first tire lever to a spoke to hold that section of the tire while the next lever is put into play.

  • The valve stem of the inner tube is somewhat more fragile than the rest of the tube, so start this removal a quarter of the way around the wheel away from the valve and continue working away so that the tire near the valve is the last and easiest to remove.

  • Pull the inner tube out of the tire, but leave the valve inserted through the rim.

  • Pump up the removed tube until it is 2-3 times normal size—big enough to hear the leak.

  • Tube analysis 101: Is it a single hole? If so, you should be able to tell if it is on the ‘top side’ or rim side of the tube. A top side single puncture indicates the need to search the inside of the tire for the shard of debris that is probably still there. Leaving the tire and tube partly on the wheel helps narrow this search.

  • A puncture on the rim side indicates that the rim cover or “rim strip” has failed. This strip keeps the spokes or the rim’s spoke holes from cutting the tube.

  • In the case of a rim strip failure, the only correct fix is to replace the strip. A Velox or similar cloth strip is worth it.  An emergency use of a power bar wrapper or the like can get you home.
  • A pair of holes—usually on the side of the tube—indicates that you’ve hit something hard enough to pinch the tire against the rim and have torn a puncture through the fold in the tube.

  • All tires loose air over time. There is so little volume in a bicycle tire that this loss is measurable in days. Road bicycle tires should be checked once a week, as they will loose as much as ten percent of their pressure per week. Mountain tires should be checked every other week.  Unchecked, this air loss makes the pinch flat more likely.

  • Replacing a new tube: put a little air into the new tube, just enough to give it shape. Start by inserting the valve into the rim and tucking this portion of the tube into the tire—which should still have one side on the rim. Tuck the rest of the tube up into the tire and then ‘roll’ the tire and tube over the center of the rim.

  • The slightly inflated tube will want to poke out over the rim's edge—it is this ‘belly over the belt’ that will get caught when finishing the tire installation.

  • Once the tube is centered over the rim, start at the valve and begin working the second side of the tire back up and over the rim. Work in both directions away from the valve.

  • Somewhere before you finish, it will get difficult to carry on by hand and you will be tempted to take up your tire lever and pry. Do not succumb to temptation! In this end zone, make sure that there isn’t some tube still stuck out over the rim's edge. Now let as much air back out of the tube as you can.

  • Push the valve stem all the way up into the tire to make certain that the base of the valve has not been trapped under the edges of the tire. Easily pull the stem back down. The final trick is to lightly brace the wheel on the ground with the valve up. Starting at the valve, pinch the edges of the tire to the center line of the rim. Working both hands away from the valve, continue to pinch the tire into the rim center and stretch the tire away from the valve toward the floor. This center of the rim is slightly deeper than the edges. By getting the sides of the tire into this center line and then all the way around, the far end that remains unfinished should now have enough slack to roll over the rim's edge by hand. Thumb strength helps, too.

  • Be confident! It will work.