Trailside Repairs: Fixing A Flat Tire

Whether you run tubes or tubeless, eventually you will have a flat out on the trail. A surprising number of riders, including Lance Armstrong, don’t know how to fix a flat tire, so here is everything you need to know to be a flat tire expert!

What to Carry

The first step to flat tire preparedness is carrying the right parts and tools. The bare essentials would include a tube, a tire lever, and a means of inflation; either pump or CO2. Here is what I carry:

If a flat can’t be fixed with this kit, it’s not fixable.

I think I have a flat, now what?

ONOZ! I have a FLAT!

First, pull off the trail. Do NOT try to ride it. You will just end up ruining the tire and possibly damage the rim. If your tire is tubeless with sealant, give the wheel a spin and then hit it with the CO2 or pump. If it seals and stays inflated, be on your way, you’re all set.

If that doesn’t work, read on…

Prepping for the Change

Before getting into the actual change, take a moment to examine the outside of the tire for any foreign object that could have caused the puncture. Look for thorns, nails, pieces of wire, etc. Also check for any long cuts or tears in the tire. If it’s just a puncture, removing the item that made it is sufficient. We’ll address cuts and tears in a moment.

Next, use your thumbs to separate the tire bead from the rim on ONE side of the wheel. Pick a spot and work your hands around until they meet up again, pressing the bead in as you go. Once that is done, insert your tire lever enough to catch the bead, pull it out over the rim, and then slide it along, working the bead out over the rim as you go. With most wheel/tire combos, the bead will come off easily. Some are a much tighter and will require a pair of levers.

At this point, you will have ONE bead of the tire off of the wheel, and the other bead will still be in place. NOTE: There is no need to remove the whole tire from the wheel. Using your hand, pull the old tube out of the tire. Remember to unscrew the collar from the Presta valve stem, if you have one. With the old tube removed, run your hand around the inside of the tire to check for anything sharp or foreign. Once you’re certain it’s clean, you are ready for a the new tube.

What if the Sidewall or Tread is Cut?

If your tire has a cut in either the sidewall or tread, we will need to patch that in order to keep the new tube in place. For this level of repair, you may want to remove the tire completely from the wheel for better access. Clean the area around the cut as best you can and make sure it is dry. Then use tape or the patch kit on theinsideof the tire to cover the whole cut. Once the patch or tape is securely in place, you can proceed as normal.

Installing the New Tube

Get your new tube out and using CO2 or pump, put just enough air into it to give it some shape. Again, going in from the side where you popped the bead off, work the new tube into the tire, making sure to line up the valve stem first. (This is where Presta valves with the threaded valve stem come in really handy.) Once the tube is fully in place, run your hand around to make sure it’s not wrinkled or overlapping itself anywhere.

Reseating the Tire Bead

Most tires will reseat with just your thumbs applying pressure. Starting at the valve stem, squeeze the bead back in place with your thumbs. For more stubborn tires, hold the wheel up in the air and while working both hands up opposite sides, from bottom to top, pinch both beads into the deepest part of the rim. This will give you just enough slack at the top to pop that last bit of bead on over the rim. If you have really stubborn tires, you will need to use your tire lever to muscle it over the edge of the rim.

Ready for inflation!

With everything in place, it’s time for some air. Attach your CO2 inflator or pump and go for it. Use the squeeze method to determine when you have it inflated to your liking, put your wheel back on your bike and resume riding, smug in the knowledge that you can do something on a bike that Lance can’t!

15 thoughts on “Trailside Repairs: Fixing A Flat Tire

  1. Good coverage on the basics. With the right tools and supplies everything will be fine.

    Now, here are two tips in case things go sideways. :)

    1. No spare tube. You have a patch kit and some time to kill, right? If not, I’ve been told it’s possible to cut the tube at the puncture and tie knots in the loose ends. Inflate, stuff into your tire, and wobble back to the trailhead. Word has it Specialized produced a similar “linear” tube that allowed you to replace a tube without removing your wheel from the bike.

    2. No inflator. Your best hope is walking out at this point but I will offer this: It is possible to put air into a Presta tube using your mouth. In fact, this works no problem for the initial inflation as you’re seating the tube in the tire. According to my research, the human lungs and mouth are capable of producing up to 19psi. I don’t dare run pressures that low even on tubeless tires but if the trail is smooth and you tread lightly you might just get away with it.

  2. @spartan, one summer I commuted to work on my mountain bike, so twice a week I swapped both tires between knobbies and slicks. I got really good at changing bike tires. :D

  3. Another tip: for fixing tires/cuts in sidewalls, there’s a few other items I’ve heard of folks using: dollar bills (fold in half) and metallic powerbar wrappers.

    Know how to change a flat BEFORE you get one.

  4. @dgaddis, I forgot about the dollar bill one, I have seen that too. If you have a carbon bike, you have to use a $20 bill… :D

    Being serious though, I always have one tube and one CO2 in my hydration pack, and if I head out on a longer ride, like Monarch Crest or similar, I also bring a seat bag with one more tube and CO2.

    If it’s an epic ride and I’m alone, I also bring the mini pump.

    Also, a 26″ tube will usually work in a 29″ tire, but NOT the other way around.

  5. Nice article and +1 for putting the glove on before using the CO2. Those things get cold!

    Another piece of advice: Check the whole tire even after you find the thorn/sliver/whatever caused the puncture. He might have brought friends!

  6. One more tip: Protect your spare tube. If it holes can easily get rubbed into them. I had one in a saddle bag along with a minitool and CO2 kit, it was all there for a long time (a year or so?) and when I finally needed it there was a hole. Now I keep it in a ziploc bag to keep friction off it.

  7. I use an old sock that has lost its partner to protect te tube but same idea. Also trying to remember if it was mentioned above but it is of utmost importance to make sure that when you are reseating the bead that the tube does no get pinched between the bead and the rim!

  8. I saw a vid somewhere online of a guy who puts long strips of those thin woven fedex evelopes (the ones you cant tear) inside his tire between the tire and the tube. I guess it adds another layer of puncture protection without adding the weight..

  9. Nice post, and comments. I picked up things I hadn’t thought of. Getting spare socks out now. Caught with out a lever, I found that the lever on axle spear worked. :)
    Remember 2 is 1 and ONE is NONE. When I leave civilization, I like multiple redundancies. I’ve got a Bontrager Air Rush (pump w/ CO2 inflater +2 16 grams CO2s) on the frame, and a Inovations mini elite co2 w/ an extra CO2 tucked in my fanny pack w/ wallet. at least 2 tubes, and some more co2′s in the camel back. I’m thinking about a second pump ;)

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