How to Fix a Flat Tire

Flat tires happen. Here's what to do when they do.

A flat repair kit, plus multitool.

Slow down gradually and steer your bike to the curb or the side of the road. Get out of traffic as soon as possible, and walk your bike to a safe place--the sidewalk, a park, a coffeeshop, wherever. If you're not somewhere you can safely stop or walk, ride slowly and carefully to keep the tire from coming all the way off the rim, and pay attention to your bike's handling.

If you live in a city with a thriving bicycle culture, you might be able to walk your bike to a nearby bike shop and have the mechanics there fix your flat for you for a few bucks. But if you don't, or if it's late or early or you're on a long ride in an area you're not familiar with, you'll need to fix it yourself. It's simple and straightforward to do so, and it's definitely a good skill to have in your mental toolbox.

You'll also need to carry a small flat repair kit, with the following items: a couple tire levers, a patch kit and/or a spare tube, and a pump of some sort--a hand pump, a frame pump, or a CO2 inflator and cartridge. Your hands will probably get a bit grubby while you're doing the repair--if that bothers you, include a little packaged hand wipe in your kit as well.

My brakes in their open position.

1. Remove the wheel from your bike. Do this by first releasing your brakes. On my bike, I do this by flicking a little lever on the brake itself, and pushing a button in my brake lever to the opposite side.

Removing a rear wheel.

If your rear tire is flat, you'll probably want to flip your bike upside down before you remove the wheel, and shift the chain to the smallest rear cog--it's easier that way. If it's your front tire, straddle the top tube and reach down past your handlebars.

Quick-release skewers open and loosened.

Next, loosen your skewers. If you have a newer bike, they are probably quick release skewers. Pull the lever on the left side of the hub, and then unscrew the nut on the other side. If your bike is older and has bolted-on skewers, you'll need to use a hex wrench to loosen them. It's not a bad idea to carry a small hex multi-tool with you even if you have quick-releases; you can use it to adjust your saddle height mid-ride and fix strange rattles by tightening loose bolts.

When your skewer is loose, your wheel should slip easily out of your front fork. To remove your rear wheel, lift it straight up and then move it away from the chain. You might find it easier to remove and reinstall your rear wheel if you push the derailleur hanger as you do so, to give the chain some slack.

The first tire lever, hooked around a spoke.

2. Next, partially remove your tire from the rim of your wheel. If there's any air left in your tube, let it out by untwisting the nut at the tip of the valve stem and pressing on it (if you've got a Presta valve) or pressing on the pin inside the valve (if you've got a Schrader valve).

Then, move your hands around the rim, pinching the tire to get it unstuck from the rim. Now break out those tire levers!

Tire levers are usually plastic; they are made in metal, too, but metal tire levers can damage rims. Plastic levers, though, have a tendency to break if they're bent too hard. This steel core lever by Soma Fabrications is the best of both worlds--a metal core to keep it strong, with a plastic outer casing to keep you from denting your rims.

Push one lever carefully between the rim and the tire bead (that's the part at the edge of the tire that hooks under the rim), at some point away from the valve. Then, lever the bead up over the rim. Some tire levers come with little hooks at the other end that you can hook around a spoke to hold the lever in place. Use another tire lever to do the same thing, as close to the first lever as you can manage (but don't worry if it's not super close). Once you've got both levers under the tire bead, you might have to wiggle them a bit until the tire pops over the rim between them.

Sliding a tire lever under the bead to remove the tire.

Then, you can run one lever all the way around the tire, freeing it from the rim on one side. You don't have to take the tire all the way off the rim, though you can if you'd like.

3. Pull out the inner tube. Be careful with the valve stem and avoid yanking at it. You'll probably find it easiest to remove the valve stem last, when you can push the rest of the tire aside most easily.

If you're in a rush, it's raining, or you don't feel completely safe wherever you are, you can skip the next few steps and install a new tube (if you have a spare) rather than patching the punctured one. Take the old tube with you and patch it when you get home--it'll be your new spare. If you want to patch your tube, read on.

4. Find the puncture. Inflate the tube and figure out where it's leaking air from. If your tire lost a lot of air all at once, this should be pretty easy. Check around the puncture you find to make sure there aren't anymore--if you got a pinch flat, there are probably two small "snakebite" holes next to each other.

If your tube had a slow leak, it might be harder to find the hole. If you can't find the puncture at all and you don't have a spare tube, your best bet might be to put the tube back on as is and pump it up repeatedly as needed until you get to your destination. Then, you can inflate the tube and put it in a tub of water--the escaping air bubbles will show you exactly where the puncture is.

Patching the tube.

5. Patch your tube. Your patch kit should come with a tiny instruction sheet, with directions roughly as follows:

- Roughen the tube around the puncture just a bit with sandpaper.

Et voila, the tube is patched!

- Apply a thin layer of glue (or "vulcanizing fluid," or whatever your patch kit calls it) to the area. Be sure to cover a larger area than the patch will cover.

- Let the glue dry. It won't take too long.

- Peel the backing off of a patch and stick it on, pressing firmly. That's it! Your tube is patched! No need to wait any longer to install and inflate it.

If you're impatient, "glueless" patch kits, with pre-glued patches, are also available.

6. Find what caused the flat! If your tire is still on your rim, you can line up the tire with your new patched tube and figure out where the bit of glass or thorn is that worked its way through your tire. Run your fingers carefully along the inside of your tire, feeling for any snags or scratches. Remove any offending bits to avoid any more flats. It sometimes helps to have something pointy with which to do this; if you have a multi-tool, something on there will probably easily do the trick.

Booting the tire with a folded dollar bill.

If there's a hole or slash in your tire bigger than 1/16th of an inch or so, you'll want to boot it--that is, place something on the inside of the tire to keep the inflated tube from squeezing out of the hole and puncturing. You can buy emergency tire boots and keep them with your repair kit, but a folded dollar bill or Power Bar wrapper (or similar) will work almost as well. It's probably time to buy a new tire, though.

The flat might also have been caused by a spoke poking through your rim tape. If that's the case--especially if you can't find anything else that might have caused the flat--replace your rim tape as soon as you can. In the meantime, you can cover pokey bits with another tube patch.

Reinstalling the tube.

7. Install your patched tube (or your spare). If your tire isn't still halfway on the rim, put it on. Inflate your tube slightly to make it a bit easier to manage, so you can stick it underneath the tire without twisting it too much. It's easiest to install if you start with the valve and work your way around in both directions from there, pushing it all the way under the tire. Be careful to keep the valve seated evenly in its hole, sticking out perpendicularly from the rim.

Reinstalling the tire.

8. Once you've got the tube all the way onto the wheel, underneath the tire, begin to reinstall the tire. This means tucking the uninstalled side under the rim again, being careful not to pinch the tube as you do so. Adjust the amount of air in the tube as needed to make this easier. Again, start at the valve, and work your way in both directions at the same time.

The last bit. (Check out the Monkey Light!)

Eventually you'll have the tire most of the way on, with a little bit still untucked on the opposite side from the valve stem. Getting this last bit over the rim and seated well is always the trickiest part. Hold the wheel on your lap with this part at the top, facing you, and use your thumbs and palms to try to work it over the edge. It might help to backtrack a little, and work back towards that point from both sides, pushing the tire up as you seat it in the rim.

Supposedly, putting baby powder inside the tire makes it slippery enough to make this process a little bit easier. If you're having trouble, it might be worth a shot. Some tires are definitely more stubborn than others!

If you absolutely can't manage to seat the last bit of tire, you can use a tire lever to lever it over the rim the same way you got it off. Be very careful when you're doing this; it's easy to pinch the tube accidentally, and then you're all the way back where you started. Hold the tire and rim at one end of the part that's still off the rim, to keep it in place, while you use the lever at the other end. Get a bit of tire over the rim at a time, and slide the lever closer and closer to your hand, until the last bit of tire slips over the rim.

Inflating the tire.

Squeeze all the way around the tire to make sure the tube and tire are seated well.

9. Pump up your tire! A frame pump is best. It's hard to fill a high-pressure road tire with a small hand pump unless you are very strong and patient, but it'll be enough get you home or to a bike shop where you can borrow a floor pump. CO2 inflators will fill your tire quickly and easily, but if they're all you have, filling and emptying the tube while you're patching and replacing it will be more complicated, and CO2 inflators produce waste in the form of used cartridges. Plus, if you get another flat and you only had one cartridge with you, you're out of luck!

10. Replace your wheel on your bike and ride on! Make sure to pick up all your tools and any trash you might have produced.

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Comments from our Readers

Thaks for the pictures

tgrudzin(chicago), submitted 8/3/2010

Never really sure what side of the repair patch was to contact the tube.