Bike Tire Basics: How to Fix a Flat
Flat tires on your bicycle, while frustrating, are easily dealt with if you’re prepared. Always carry a spare tube, repair kit, tire levers and a pump and follow these simple directions to get back on the road quickly.
Here are the basic steps to fixing a flat:
- Remove the bike wheel
- Remove the tube
- Find the cause of the flat
- Repair or replace the tube
- Reinstall the bike wheel
Video: Fixing a Flat Tire
Remove the Bike Wheel
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, 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.
Then, Release Your Wheel
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: 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 for details on its particular release-and-retention system. Or consult with a bike pro at your local REI.
Rear wheel: 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 crank the pedals 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).
Video: Removing the Rear Wheel
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.
Remove the Tube
To find the source of a flat tire and fix it, you need to remove the tube from the tire.
Getting Inside Your Bike Tire
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.)
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 should 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
While removing the tube, it's important to look for 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.
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 to feel for air 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 spoke-hole opening.
Once the tube damage has been found, check your tire for damage as well. Use the valve stem to align the tube so you can find the same location on the tire. Look for any embedded objects in the outside tread. Then carefully feel and look inside the tire, making your way slowly around the tire. If you have taken the tire completely off the rim, turn the tire inside out and do a full visual inspection. If you find any cuts, squeeze the ends of the length of the cut to push apart the rubber and look for anything embedded in the tire. Remove any foreign debris.
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: 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.
Typical patching steps:
- 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.
Replacement: You must replace your tube any time the damage is too extensive or severe to patch, when a patch job fails to hold or when the tube’s valve is damaged.
Replacing a tube is simply a matter of using the right size. Size information is sometimes available on the tube itself, on the sidewall of your tire or in your bike owner's manual.
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.
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.
- Starting with the valve stem, lower the tube onto the wheel, inserting the valve into the rim valve hole. Check that the valve stem is straight and not at an angle.
- Then place the rest of the tube inside the tire.
- If you completely removed your tire from the rim while fixing your flat, push one edge (or “bead”) of the tire inside the rim.
- Beginning at a point opposite the valve, push the other tire bead inside the rim.
- Proceed around the wheel (in both directions at the same time), working more of the tire bead inside the rim. 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. Use caution when using a tire lever to avoid pinching the tube.
- 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.
Reinstalling the Bike Wheel
Start by positioning the wheel so the top section of chain is draped over the smallest cog in your cassette. As you move to install the wheel, line up the dropouts on the bike frame with the axle. While lowering the bike into place, pull the derailleur down and back to get it out of the way and reduce resistance. Push down gently on the saddle and make sure the axle is securely seated in the dropouts. If the wheel doesn't slide in easily, remove it and try again.
Now, hold the quick-release lever in place and tighten the bolt on the drive side of the bike. Once the bolt is tight, close the lever. Make sure it's tucked out of the way and not touching the bike's frame. If the lever closes too easily and is touching the frame, it's probably not tight enough. Open the lever and tighten the bolt some more.
If your bike has caliper or cantilever brakes, remember to reconnect them and make sure they're working.
Finish by spinning the pedals and making sure the gears shift normally.
Line up the the dropouts in the fork with the axle of the front wheel and slowly lower the fork onto the axle. Push down gently on the handlebar to make sure the axle is seated in the dropouts.
Hold the quick-release lever in place as you tighten the bolt. When the bolt is tight, close the lever. Make sure it's tucked out of the way and not touching the bike's frame. If the lever closes too easily and is touching the frame, open the lever and tighten the bolt some more.
Reconnect the brakes and make sure they're working.
Learn more in our article, How to Remove a Rear Wheel with a Quick-Release Axle.