Tuesday, April 1

Spring Cleaning: Fixing Flat Tires (2/5)

You know what really grinds my gears? I hate when don't ride my bike for a couple days, and then when I go to ride it again, it has a flat tire. I mean, seriously, what the hell. They were full when I parked it. Are there like gnomes that come in the night and steal the air out of my tires, or what? Having to stop and change a flat when I just want to get out and ride is such a pain.

Leaky Bike Tubes

Bicycle tubes will always lose their pressure over time--either because of the porous nature of rubber, or because of a slow leak. If you filled your tires yesterday, you can tell which you have.

Poke your thumb in to the tire again; how is it?
  • meh, same I guess:
    Congratulations, your tires are ready to rock. Just make sure you remember to check them before every ride and pump them up if they start to feel low again; they will inevitably get low over time.

  • a bit deflated, but not totally flat:
    A slow leak. You're probably best off applying a patch. Slow leaks are common, and if you replace your tube every time you get one, your tube budget can get out of control. patch kits, on the other hand, are cheap as dirt.

  • totally, totally flat:
    You probably have a more serious puncture. You probably just want to replace the tube.

Fixing Flat Tires

I've got a slow leak in my rear tire that I've been putting off fixing for weeks--I've just been filling it up every morning before I ride. I'm just going to put a patch on it. Here's a little slide-show:

  1. Remove the Tube
    Take off the wheel, and let the rest of the air out of the tire. Now extract the tube. The easiest way to get the tube out is to use a tire lever and pry the bead of the tire off the rim by sliding the lever around the edge. For the love of God, don't use a screwdriver; you'll just mess up your tires. Pull the lever around the rest of the way and it should slide the edge of the tire right off the rim. Once you're there, it's fairly easy to pull the whole tire off the rim, then pull the tube out of the tire.

    Next, run your fingers carefully around the inside of the tire. You're looking for any sharp burrs or anything that could have caused the puncture. I find it's usually a tiny metal burr. If you find anything, dig it out.

  2. Find the Hole
    When you have a slow leak like I do, it can be really hard to find where it is--it doesn't have enough pressure to hear the air, or even feel it. The best way is to inflate the tube a little bit, then put it underwater and look for air bubbles. When you find them, make a note of where the hole is, and then dry off the area around it. Of course, you won't have a bucket of water available on the road, but you can ride a slow leak long enough to get home anyway.

  3. Patch the Tube
    If you have a patch kit, there's usually a little piece of sand paper in there. Use it to scuff up the area around the hole. This makes the tube more receptive to the gluey stuff, and also gets the layer of grime off of it. Squirt a little of the vulcanizing stuff from the kit on the area. It's better to have unpactched glue than unglued patch, so spread it wide. let it dry for a moment, and then press the patch on.

  4. Put the Wheel Back Together
    There are a few ways to do it, I do it this way:
    Put the tire half-on the rim so that one bead is in the rim, one is off the side. Inflate the new or patched tube slightly so it is easier to work with. Get the tube valve in to the hole (make sure it's straight, if it's angled, it can peal and break) then work the tube in to the side around the circumference of the wheel. Make sure the tube is settled in the rim, then use the tire lever to pry the bead of the tire on to the rim. Now pump your tire up to is recommender PSI.
Flat tires are inevitable, and being able to fix one is only slightly less critical of a cycling skill than being able to balance. Check your tires before every ride, and fill them up! Tomorrow: Cleaning.

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