Flat tires on your bicycle, while frustrating, are easily dealt with. The causes are numerous, ranging from a leaky valve to the obvious blowout. But no matter the reason, these simple directions can get back on the road or trail quickly.
It's much easier to fix a flat if you first remove the wheel from your bike. Removing the wheel is a 2-step process:
First, Release Your Brakes
Most brake assemblies sit very close to your wheel rims and use a quick-release system to disconnect and reconnect them. The exact location and design of these release systems will depend on your style of brakes.
● Some have a knob at the end of the pull-cable that catches on a notch in the caliper arm. Squeeze the brake arms together to release the cable.
● Others have a quick-release lever, just like on your axle, which can be opened to release the brakes.
● If your bike has disc brakes—most mountain bikes have these—be careful not to touch the rotor when opening the quick-release mechanism. The rotor is located very close to the quick-release lever and can become hot enough to burn you.
Once you've disengaged the brake assembly, your wheel is still held to the frame or fork (depending on if it's the rear or front wheel) by the wheel axle. To release the axle, check to see if you have a quick-release lever—most bikes have this—or a bolt-on nut and then follow the steps below.
● Front wheel: To remove a front wheel, simply open the quick-release lever and unscrew the securing nut slightly on the opposite side as needed to release the tension holding the wheel in place.
Note: Some bicycles have retention devices designed to hold a wheel in place even when its quick-release lever is open. If your wheel doesn't pop out after you open the quick-release lever, check the owner's manual that came with your bike for details on its particular release-and-retention system. Or consult with a bike pro at your local REI.
● Rear wheel: Removing the rear wheel is almost as easy as removing the front wheel, but the chain presents an added complication. See our video below or follow these instructions.
Before removing your rear wheel, shift your chain onto the smallest rear cog. To do so, adjust the shifter up then raise your bike and spin its wheels until the gear-shift is complete. Turn the bike upside down, then turn the rear axle quick-release lever until it's fully open. You may need to unscrew the nut slightly on the opposite side. Pull back on your rear derailleur to give yourself some slack, then lift out the wheel with your other hand. The wheel should pop free without getting tangled in your chain. If your wheel stays put, it's likely there's a retention device holding it in place (see the note above).
These work just like quick-release axles except that they must be loosened with a wrench instead of a lever, so it takes a bit longer.
To loosen a bolt-on axle, simply grab both ends of the axle with 2 good-fitting wrenches and turn both wrenches a couple of full turns. If you only have one wrench, alternate between ends of the axle bolt, loosening each a half turn or so at a time.
If you're removing a bolted rear wheel, follow the procedure described above to avoid getting it hung up in your chain.
It's important to find the origin of your flat tire. It may be a nail that is now long gone, leaving you with a hole in your tube and tire. Or it may be a thorn or piece of glass that is still stuck in the tire and could damage your newly repaired or replaced tube.
When searching for the cause of a flat, begin on the outside and work your way in.
● First, check the outer surface of the tire for any signs of damage or wear—things like foreign objects lodged in the tread, cuts or tears in the tread or tire sidewall, or worn/cracked tread patterns.
● Next, get inside the tire (see below) and check both the inner tube and the inside surface of the tire for similar damage.
Most bike tires are held inside the rims with a combination of physical grip and air pressure. The grip comes from the edge—or "bead"—of the tire interlocking with the edge of the rim. The pressure comes from the inflated tube pressing the tire against the rim.
First, release all of the remaining air from your flat tire by depressing the small plunger in the center of your tire valve (Presta valves must be opened first. To do so, remove the valve cap and turn the valve counterclockwise.) Next, unseat your tire bead using the following procedure:
● Attempt to unseat your tire by hand by pushing one bead edge in toward the center of the rim. If this doesn't work, use tire levers to get some additional leverage.
● When using tire levers, start on the section of your tire opposite the valve (to avoid damage to the valve stem). Use the longer end of one tire lever to pry the bead of the tire up and over the edge of the rim.
● If you can't unseat the tire with just one lever, place a second one in a similar manner, 2 or 3 spokes to either side of the first. (Tires levers come with a handy notch that can be secured against a spoke, keeping the lever in place.) Some tire manufacturers suggest sliding the second lever along the rim away from the first to unseat more of the tire. Others suggest using a third tire lever instead to avoid possible tire and/or rim damage.
Once a section of the tire bead is free, you should be able to unseat the rest of the bead with your fingers. Remove the inflatable tube from beneath the tire by pulling the valve stem out through the rim first. The rest of the tube slide out easily when pulled. Be careful when pulling the valve out through the rim, as its sharp edge could damage the valve.
Finding the Cause of Your Flat
Tube damage can be difficult to spot. If you don't see any obvious punctures or blowouts, try inflating the tube so you can check for escaping air. To find very small leaks, pass the tube close to your eye or submerge it in water and look for bubbles.
Tip: Leave the tire in its same location on the wheel so you can check for tire damage once the tube leak is discovered.
If you can't find any tube damage, check the valve. If the valve stem or base is cut, cracked or severely worn, it may be leaking. If so, the entire tube will need to be replaced.
If the valve is in good condition, check the thin strip along the inside of your rim. Look for protruding spoke ends or areas where the strip may have come free and pinched the tube against the rim surface.
Once the tube damage has been found, check your tire for damage as well. Use the valve stem to relocate the tube so you can find the same location on the tire. Look for any embedded objects in the outside tread. Then turn the tire inside out and do a full visual inspection of the inner surface, making your way slowly around the tire. If you find any cuts, squeeze them to pull apart the rubber and look for anything embedded in the tire. Use a tweezer to remove any foreign debris.
Step 3: Repair/Replace the Tube
If your tire has sustained little or no permanent damage (as is often the case), your decision will be whether to repair your tube or replace it.
Repair: Repairing a bike tube is easy once you get the hang of it, and it is more inexpensive as well. Most commercial patching kits contain everything you need to create an effective patch in the field, including step-by-step instructions. However, patching a tube should be considered an emergency repair. For maximum reliability and safety, replace a patched tube as soon as possible.
Replacement: This is the best and, in some situations, the only solution to a flat tire. You must replace your tube any time the damage is too extensive or severe to patch, or when a patch job fails to hold.
Note: Replacing tubes is more expensive than patching them. However, the resulting tire/tube combination is generally stronger and longer lasting than a patch job. To repair a bike tube, follow the instructions included in your tube-repair kit.
● Find the damaged area.
● Clean and dry the damaged area.
● Rough up the surface of the damaged area with sandpaper (to help the glue adhere).
● Spread the glue (vulcanizing fluid) and allow it to set until tacky.
● Apply the tube patch and hold it in place with pressure.
● Apply talc to repaired area once the glue has bonded to make the tube easier to reinstall. Talc should also be applied to the inside of your tire.
Replacing a tube is simply a matter of using the right size. Size information is available on the tube itself, on the sidewall of your tire or in your bike owner's manual.
Putting Your Tube and Tire Back On
● Make sure the rim strip is seated properly.
● Partially inflate your new or repaired tube to give it shape and ensure it holds air.
● Then place the tube inside the tire.
● Starting with the valve stem, place the tube and tire onto the wheel.
● Reseat one edge (or "bead") of the tire completely.
● Beginning close to the valve, reseat the other tire bead inside the rim. Check that the valve stem is straight and not at an angle.
● Proceed around the wheel (in both directions at the same time), reseating more of the tire bead. This will get harder as you go.
● Pinch both sides of the tire in towards the center of the rim to make things easier, or carefully use a tire lever to complete the job.
● Once the tire and valve are in place, check along its edges to make sure that the tube is not caught between the rim and the tire bead. This could cause another flat.
Now inflate your tire slowly, checking both sides of the rim to make sure that the tire bead stays firmly seated. Double-check the valve as you go to ensure it remains straight. To make sure your tube doesn't get caught between your tire and the rim, go around the whole tire once and pinch both sides of the tire inward.
Inflate the tire to its recommended pressure (printed on the tire itself or in your owner's manual). If you don't have a gauge, use your thumb as a guide. If your thumb presses in easily, keep pumping.
Step 4: Reinstall the Wheel
Simply reverse the procedure you used to remove it. Reattach the wheel to your frame dropouts, holding the derailleur out of the way if you're reinstalling the rear wheel.
If a bolt-on axle holds the wheel in place, you must tighten it securely. If a quick-release mechanism is involved:
● Make sure the quick-release lever is open before reinstalling the tire in the frame dropouts.
● Make sure that the wheel is installed evenly, centered in the dropouts.
● Turn the quick-release lever to the fully open position, then turn the adjusting nut on the opposite side of the axle clockwise until it resists turning (don't use a tool to tighten this nut).
● Close the quick-release lever. Resistance should begin when the lever is sticking out perpendicular to the bicycle frame, then build until it is fully closed and pointing towards the rear of the bike.
Finally, flip the bike right-side-up. Be sure to reattach your brakes before riding!
Carry a spare tube: It's always wise to carry an extra tube. Just make sure you have the right size. Your tube size is indicated on the sidewall of your tires and in your owner's manual. Also note whether it uses a Schraeder or Presta valve.
Carry a patch kit: This is a compact and economical alternative to a new tube. The downsides? They are more hassle and offer a somewhat less durable solution.
Carry tire levers: These easily fit into even a small underseat bike bag.
Carry a pump: Some flats can be avoided by simply riding on tires that are properly inflated. Check your air pressure before every ride.
Contributors: Karl Schumacher, Novara bike tech rep; Shawn Pedersen, REI Seattle master bike tech.