Make sure your kit is complete before every ride. I also highly recommend that you check and replace your patch glue every couple of months. That stinky goo has a tendency to dry up just before you need it. And forget that glue less patch. Unless you have latex tubes, they are worthless. A small rag is also a good idea, as well as something to pry foreign objects out of tires.
If your front tire is flat, stand over your top tube and release the brakes so that the pads clear the tire. On a road bike, there should be a lever where the cable is bolted down at the brake arm. Pull this lever up towards you.
For “V” type brakes found on mountain bikes, push both arms in by hand until the pads contact the rim. This will create enough slack in the cable to free the “noodle” from the slotted cable stop on the brake arm. If your rear tire is flat, release the brakes, shift down to the smallest cog on the rear cassette, and turn the bike over so it is standing on the seat and handlebars.
Disk brakes require no tricks when removing a wheel, however, never squeeze the lever on hydraulic systems when the wheel is not installed, the pads will not return all the way – very bad.
Pull your quick release lever into the open position, hold the nut on the other side, and spin the lever counter-clockwise until the hub can clear the dropouts. For a front tire flat, remove the wheel and let the bike stand on the forks. For a rear flat, with your bike upside down, use your small rag to hold the chain out of the way while you pull the wheel straight up out of the dropouts. There should be minimal interference from the derailleur when the chain is on the smallest cog.
Remove the valve cap and the stem nut (presta tubes), open the valve and depress it to release any remaining air. For a shredder valve (car valve), remove the cap and depress the recessed pin with a small allen wrench to release air.
Now, with all the air released, work your way around the tire with your thumbs, pushing the bead (edge) of the tire up and away from the rim. Do this all the way around the tire, and then do the other side. Make sure that the tire is not sticking to the rim anywhere.
What you have done is create slack, which can now be pushed to one area on the rim. Imagine a bus steering wheel, your hands at 9 o’clock and 3 o’clock. Hold your wheel like that with the edge against your thighs. Now work your hands around the tire towards 12 o’clock, pushing the tire inward toward the hub and upward until the bead has enough slack to pop over the top of the rim.
Grasp the tire with both hands at the top of the rim and with your thumbs, push the bead in, up and then roll it forward over the edge of the rim facing you. Now slide your fingers under to loose edge of the tire and pull it away from the rim until one entire side is off. Remove the damaged tube. Save the patch job for home.
Don’t slide your fingers under the loose bead of an old tire. If the rubber is worn away, it could cut you. Use levers on old, sun damaged tires, or tires that are just too stubborn. It will make the levers work that much more smoothly.
With your tire half off the rim, or all the way off if you prefer, inspect the outside of your tire for foreign objects.
Thorns, nails and the like are usually easy to spot and can be flicked away with a pointy tool. Glass can be harder to spot.
Look for cuts in the tire casing, and probe them with the pointy tool, you will often find bits of glass, which if not the cause of this flat, will be the cause of the next. Get them out of there. Once the outside has passed inspection, gingerly run your bare fingers along the inner surface of your tire and remove any offending bits.
At this point you should also inspect your rim tape for any cuts at the spoke holes, or spokes poking through, especially if there is no other apparent reason for the flat. If spoke ends or failing rim tape is to blame, cut a piece of tube patch and put it under the tape where it is damaged.
If you removed the tire completely from the rim, reinstall one side of the tire. This should be relatively easy – just put one edge over the rim and work it around with your thumbs until it pops on. Grab your new tube and inflate it just enough to hold a little shape and close the valve (presta).
Now find the valve stem hole, insert the valve stem and install the stem nut loosely if you have a presta tube. Push the tube up into the tire all the way around. At the valve stem, push the loose bead of the tire back onto the rim and work the tire on with your thumbs.
If you have trouble getting the last bit of edge, or “bead” onto the rim, let the air out of the tube and repeat the slack creating process you mastered earlier. This will allow the tire bead to pop over the rim. Reinstalling a tire without tools eliminates “lever bites” (lever punctures. Now that the tube is installed and the tire is on the rim, you can pump it up and get rolling.
The wheel still has to get back on the bike. The front is fairly easy: just stand over the top tube, lift up the front fork, slide the wheel into the dropouts (with the quick release lever on the left side), tighten it up, and close the lever. The lever should leave an indentation on your hand, but should not be painful to close. Don’t forget to secure the brakes now.
For the rear wheel, lift up the chain with your rag and line the small cassette cog up with the chain where it runs over the top pulley on the derailleur. Since the derailleur was dropped to the smallest cog when the wheel was removed, the axles will line up with the dropouts. Gently work the wheel down and back until it drops in. Make sure that the axles are all the way seated in the dropouts then close the quick release lever. Turn the bike over and secure the brakes.
Give the wheel a spin to make sure there is no brake rub. Watch the tire for even spinning. A wobble or dip in the tire means that the bead of the tire is not seated correctly on the rim. To remedy this, lay the bike on its side, deflate the tire until it is soft, but not flat, push the tire up and away from the rim with your thumbs at the site of the dip, which will cause the tire bead to pop into place. Now re-inflate.
