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Bike repair: Flat tires

Filed Under: cars and transportation, fix-it

Bike Repair: Change a tube(click thumbnails to view gallery)


If you ride a bike, you know the frustration of having a punctured tube. Suddenly, you are immobile. And that sucks.

Luckily, changing a bike tire tube is easy, but it requires a critical tool. The tire lever is vital to changing a tire, and if you have two of them, the work is cut out for you.

Slip the tire lever under the bead of the tire and pry the bead out from the rim. Then hook the lever tool onto a spoke, and, using the other lever, pry out more of the tire and then slide the free tool around the rim, pulling the bead out until that side is removed.

Removing the tire is easy. Carefully extract the valve stem -- the little tube you inflate the tire through -- from the rim, and then peel the tire and tube out of the rim.

Inspect the tire and tube for damage. In the photos, my tube has a puncture in it from a sharp, metal road hazard, probably a roofing nail. It also sliced through the tire itself, but hopefully you won't have this problem. The tube is the thing you want to pay attention to.

The hole in my tube is easily detectable. Nail punctures or other minor tears may not be so obvious, though. If your tire has a slow leak, chances are the hole is TINY. To find the puncture, put some air into the tube and submerge it in a bathtub or basin of water. Holding the tube under, inspect the tube closely for bubbles rising from it. Where there are bubbles, there's a leak. If you can't find it, put a little more air in the tire (in case the hole is so small that it only leaks under higher pressures), and repeat. If it's impossible to find a hole, you might have a problem with the valve stem. Submerge it, and gently work it around with your fingers to see if any cracks at the base of the stem are the culprit.

Once you find the damage, and it's not too bad to fix, you'll want to patch the tube. To do this, you'll need a kit with patches, sandpaper, and vulcanizing fluid (in a small tube). Sand the damaged area, spread vulcanizing fluid in the area around the hole (not too much, but you definitely want to cover the area where the patch will go), and wait for the fluid to set. This takes about 5 minutes.

Then carefully apply the patch, holding it on firmly and pressing all around it. Pinch it on and try to make sure it's contacting the whole area with the tacky fluid on it, and make sure the hole is as close to the middle of the patch as possible.

Let that set for a minute (with you holding it firmly, but not too hard) before you carefully remove the plastic backing from the patch. If the patch starts to peel up, you might need to sparingly put more fluid on the area, and then hold it in place firmly for a minute or two. The patch should peel off without too much hassle.

Replacing the tire is practically the opposite of removal. Put one side of the tire around the rim. You can do this by hand by pushing the bead of the tire over the rim and following it with your fingers around the rim until it pops on, and then carefully slip the tube back into the tire. Start with the valve stem, and be careful. I can't count the number of times I have replaced a tube but was careless with the stem, and ended up cutting the tube unintentionally right where the stem meets the tube. That sucks mightily, and I urge you to avoid this. It can produce a slow leak or a quick pop, and both of these outcomes are undesirable. Be attentive. The tube you save may be your own.

Seat the tube all the way around the inside of the tire, making sure it's not going to pinch against the rim. Push the un-inflated tire into the tire, feeling for twists or bunched up areas of the tube. Make sure the tire and tube are smooth against each other.

Then, using your fingers at first and then the levers, press the second side of the tire onto the rim. The bead will go on about 3/4ths of the way around the tire, then you'll have to use the levers again. It's a bit tricky at first, but once you do it you will feel confident and virile. Pump the tire up to acceptable limits, put it back on your bike, and ride away.

Note: You must make sure if you are replacing a tube that you get the proper size. Standard rim sizes are 26" and 27", and widths vary by tire. Some popular tire sizes are 26" x 2" and 27" x 1 1/4". Tire size is usually printed on the sidewall.






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