How to Repair a Flat Bike Tire

Getting flats is part of bike riding; if you haven’t had one yet, your day is coming. Flat repair is easily the most common repair we perform in the shop, and while we’re happy to do it, it’s an inconvenience to get one while you’re out if you don’t have what you need, and know how to fix it. Luckily, flat repair is easy for anyone to do, and requires little in the way of tools.

Flat repair tools

These are all the tools you need: a fresh tube, a set of tire levers, and an inflation method.

What you’ll need:
1. A fresh tube or patch kit
2. Tire levers
3. Inflation method

Step 1: Get the wheel with the flat tire off the bike.

Tire lever inserted under bead of tire.

Insert the tire lever between the tire and rim, and lever down.

Step 2: Wedge a tire lever under the bead of the tire and run it around the wheel, unseating the tire from one side of the rim. There’s no need to pull the tire completely off the rim unless you really need to examine it closely to figure out what caused your flat. Most tire levers have a slot at one end for hooking around a spoke. This is handy if your tire fits the rim very tightly because it holds one lever in place and frees up your hand to work another lever in. Most of the time, one lever will do the trick.

Slide tire lever around rim

Work your way around the rim with the tire lever to unseat the tire from the rim

Step 3: Determine the cause of the problem. This is really the trickiest part. The best way to do it (if you’ve got access to a pump or compressor) is to inflate the punctured tube and find where the air comes out. Sometimes it’s really obvious; sometimes less so. What you want to do is find the hole and then relate it to a cause in the tire/wheel. Is it on the outside of the tube (the part pressed up against the inside of your tire)? Then there’s probably something stuck in the tire, most commonly glass, wire, or thorns. Carefully run your fingers through the inside of the tire, feeling for any sharp edges. Most of the time they’re pretty easy to spot and you just pull the cause out. If you don’t feel anything, carefully study the outside of the tire while feeling the inside, looking for cuts or lodged pointy things (you’ll be surprise at all the junk that you’ve been carrying around in your tires). If the hole is on the inside of the tube (the part pressed against the wheel), you want to study the wheel itself. Is the rim strip properly covering spoke holes? Are there burrs in the metal or rusty spots that can rub the tube? The most common problem that we see here is called a pinch-flat. A pinch-flat occurs when you ride under-inflated. When you roll over an edge, like a curb or rock or root, on an under-inflated tire you can pinch the tube between the tire and the rim (pump up your tires regularly and you’ll pretty much eliminate pinch-flats). Once you figure out what caused your flat, and remove or fix it, you’re ready to replace the tube. Be careful and thorough here; if you don’t eliminate the cause, you’re going to be flat again pretty quickly.

Insert new tube into tire

Carefully insert a lightly inflated tube into the unseated tire, starting at the valve.

Step 4: Insert the new (or patched) tube into the tire. Start by putting a little air in the tire to give it some shape (this makes it easier to work with). Insert the valve stem through the hole in the rim, and then shove the tube into the tire.

Reseat the tire

Carefully reseat the tire back onto the rim, being careful not to pinch the tube in doing so.

Step 5: Re-seat the tire back onto the rim, starting in one spot and working your way around the wheel. Be careful not to pinch the tube as your pushing the tire into place; sometimes you have to manually shove the tube into the tire and hold it there while you re-seat the tire.

Inflate new tube, checking for for proper seating

Carefully check that the now inflated tire is neither bulging out of, or sucked into the rim at any point. It should look like this all the way around and on both sides.

Step 6: Inflate. Pump the tire up enough that it assumes its basic shape, but not so much that you can’t squeeze and move the tire around. Check that the bead of the tire is neither bulging out nor sunken into the rim. If you get this wrong, you’re about to hear a loud “BANG!” when the tube bulges out between the tire and rim and basically explodes in your face. This happens occasionally to everyone and will leave your ears ringing. Once you’re confident that the tire is properly seated, go ahead and pump it up to the recommended pressure (it’s stamped or printed on the sidewall of your tire if you can’t remember what it is). When you’re done, check it out again to make sure there are no bulges or sunken spots.

Step 7: Put the wheel back onto your bike. Before you hop on, spin the wheel and squeeze the brakes. This does two things. First, it verifies that you remembered to reattach the brakes after putting the wheel back on. Second, it shows if the wheel is straight or crooked in the dropout. Do they stop the wheel? Now spin it again; does it rub at any point? If not, you’re ready to go.

That wasn’t so hard now, was it? Let us know if you have any questions!

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About Josh Bolick

Josh Bolick works at Florida State University Libraries in the Office of Scholarly Communication.
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