How To Fix Your Flat Tire

| June 24, 2014 | 1 Comment
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Pack essentials for fixing a flat: spare tube, pump, and a pair of tire levers. Photo by Tristan Von Duntz

(Ed. note: This is the first in a series covering common bike repairs in a mountain bike trail setting. Many of these repairs can be applied or adapted to road bikes as well.)

You’re riding along on your favorite trail and, all of a sudden, POP! HISS! Or maybe there’s no sound at all, but either way, that wobbly-tired sloppy feeling coming from your wheel is a sure sign: You’ve got a flat.

If you’re like me, you’ve chosen your mountain bike pack for its fabulous color and myriad of compartments for storing everything from lip balm, car keys, snacks, an extra layer, and the earring your forgot to remove at the trailhead. That might sound a little “girly,” but those compartments are also for packing all the essentials to fix that flat yourself, and there’s nothing girly about that.

First and foremost, never ride on a flat tire. Doing this will damage the underlying wheel rim and those are expensive to replace. Next tip: Work off of the trail, so as not to mess up the flow of other riders coming down behind you.

Follow these instructions (and practice a few times at home to be sure). Then you’ll be back on your way.

The Gear

To fix your flat, you’ll need the following in your pack, or you’ll be hiking that bike back to the trailhead:

Portable pump
Spare tube (26-, 27.5- or 29-inch to match your wheel size)
A set of tire levers (having two is helpful, but in a pinch a strong stick will help)
A tube patch kit (for multiple flats)
Stanz NoTubes or other tubeless sealant (for tubeless set-ups only)

Tubeless Wheels

If you’re running a tubeless setup, then your wheels do not have tubes inside the tire. In this case, the tire has been sealed with a special sealant designed to close any punctures to the tire. This setup is preferred by some riders because it keeps flat repair easy. Inspect the wheel for any major gashes and, provided those are absent, simply spin the wheel a few times to get that sealant in motion and give it a few minutes to re-seal. Re-inflate the tire and be sure you’re not still leaking air by listening for hissing or watching for deflation. If you’re re-sealed, you’re good to go. If you’re still leaking air or if your tire has a significant gash, you can repair it by following the instructions below. It is a good idea for tubeless riders to carry a spare tube just in case.

Removing the Wheel

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Use one tire lever to hold the bead outside of the rim while you work the second tire lever around the wheel, removing the bead as you go. Photo by Tristan Von Duntz

To replace or add a tube, you’ll need to first remove the wheel from your bike. This can be relatively easy, provided you have quick release levers and disc brakes, which most modern bikes are equipped with. To remove the wheel, you’ll need to loosen the wheel from its hub and brakes.

Getting the front wheel off is a cinch: Simply flip open and loosen your lever or and pull the wheel from the hub. For cantilever brakes you’ll need to first undo the cable running into the brake by squeezing the two brake arms together to give slack in the cable, and then sliding the cable out of its notch.

The rear wheel can be a pain because here you have the chain, cassette and rear derailleur to contend with. First, shift your bike into the smallest ring of the cassette and flip your bike upside down to rest on the handlebars and seat, with the wheels in the air. To remove the rear wheel, you’ll loosen it the same as the front, and then guide the wheel out of the frame, being careful of the cassette and chain. It is a good idea to practice this at home a few times.

Finding the Culprit

Once your wheel is off, you can do a visual check for the source of your flat. Look for anything noticeably sticking out of your tire—you’ll want to remove any foreign objects to avoid another flat. Then, you’ll loosen one side of the tire from the wheel rim. You’re not taking the tire off, but rather exposing the inside so that you can replace the inner tube. Once the tube is out, you can do a second check for the culprit on the inside of the tire (see “Removing the Tube” below for more details).

Opening the Tire

To open up the tire, hold the wheel in front of your legs while standing and work on the side facing away from you. Pry the skinny end of your tire lever under the bead of the tire and the wheel rim at the top of your wheel and leave it there, with the notched end of the lever secured on a spoke. This lever will help to hold the bead outside of the rim. Pry your second lever under the tire bead right next to the first, then hold this second lever in your fist and guide it downward under the bead and along the rim of the wheel toward the bottom of the tire, pulling the bead out of the rim as you go. From the bottom of the wheel, work your way back up the top of the wheel. Be sure to leave the opposite bead, or the other side of the tire, inside the wheel.

Removing the Tube

Next you’ll remove the tube, starting at the air valve. Unscrew the valve cover if you have one and remove the washer, and pull the valve out of its hole. Now you can pull the entire tube out of the wheel. Throw the old tube in your pack. Remember: pack it in, pack it out.

An important, and often overlooked, step occurs here: Check your tire for foreign objects like grass, sharp rocks, sticks, or barbs that could have punctured it. By not removing any foreign objects, you’re setting yourself up to pop your spare tube, too. To check, very carefully run your fingers all over the inside of the tire feeling for sharp objects, being careful not to cut yourself on any sharp foreign objects. If you know the exact point of puncture, you can focus your search there, but do inspect the whole tire. Remove any foreign objects.

Fixing a Gash in the Tire

In the case of a gash in the tire, you’ll need to patch the tire itself. This can be done with a variety of things you may have with you: a wrapper, dollar bills, scraps of your old tube, or any other sturdy flat material. The objective here is to cover the gash; otherwise, your new inflated tube will squeeze out of the gash and most likely get popped. This trick will get you out of the woods, but you’ll need to do a proper repair job or replace the tire once you’re back at home.

Installing the Tube

It’s time to install the new tube and pump your tire back up. Start by pumping some air into the tub until it holds a circle shape. Start at the air valve, first removing the cover and washer from the new tube and then feeding the valve through the hole in your wheel. Place the tube

Push the new tube inside the rim and tire. Photo by Tristan Von Duntz

Push the new tube inside the rim and tire. Photo by Tristan Von Duntz

inside the rim all around the wheel. Do not fill the tube all the way until after you reinstall the tire.

To reinstall the tire, use your fingers to put the bead back into the rim. Pinch both sides of bead into the middle where the rim is deeper, giving you more room to work with. Continue working around the wheel adding the bead back in and pinching both sides toward the middle. When the tire starts to get tight around the wheel, this can become too difficult to do with your hands. Though some experts will advise against it, using your tire lever can help to pry the bead back into the wheel. Just be very careful not to pinch or tear the new tube with your lever. This can take some force!

With the tire back in place, roll the wheel around on the ground while applying some weight to it. Pushing down on the wheel forces the air to move around in the new tube and work out any kinks. Roll the wheel around several times, being sure to cover the full circumference of the wheel. Doing this will avoid and folds or pinches that could prevent your new tube from inflating properly. Once you’re sure the new tube is well seated, fill the new tube back up to your preferred pressure.

Reinstalling the Wheel

Now you’re ready to put that wheel back on! Again, the front is a cinch: Just pop it back on to the fork being careful to line your brake rotor on the wheel into the space between the brake pads on the fork, and then tighten and close your quick release lever. If you have cantilever brakes instead of disc brakes, re-attach the brake.

As with taking it off, the rear wheel needs more careful navigation of its association parts. Line the teeth of the smallest cassette ring up with the chain below it, and drape the chain above the cassette. Lift the rear derailleur and move the wheel towards the cranks (forward) so that it can drop into place, guiding the rotor between the brake pads. If you instead have cantilever brakes, re-attach those after the wheel is back in place.

After getting your wheel on, it is a good idea to make sure it’s seated properly in place on the bike frame. To do this, give the wheel a spin. It should spin freely and quietly. Noticeable wiggles from side to side, abrupt slowing or stopping or skipping sounds all indicate that the wheel is not properly installed. In this case, re-do the installation before heading on down the trail.

Ride On

You’re good to go, and you’ve fixed it yourself. Happy trails!

Category: Blog

Sarah Galbraith

About the Author ()

Sarah Galbraith (of Marshfield Vermont) eats, sleeps, and breathes bikes. She strives to inspire others to do the same through teaching, leading, trail building, and writing. She is co-founder of her local mountain bike club, ambassador to her state’s mountain bike association, and will soon be parenting a brand-new mountain biker. Follow her at www.greenmountainlines.blogspot.com.

Comments (1)

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  1. Mary Spence says:

    Thanks! Great article!

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