Fixing Flats
Tech Center  |  Fixing Flats
Ah yes, everyone's favorite, the flat tire. It happens to us all. Once you've calmed down, stopped jumping up and down and cursing and stopped throwing things around, you'll still need to fix that bad boy. This page will help you do that.


There are 3 ways to fix a flat. Take it to a bike shop, patch the inner tube or install a new tube.

If you're ready to tackle the task yourself, we recommend you install a new tube. Patching tubes is not very reliable. Unlike many years ago when tubes were made of mostly natural rubber, today's tubes are made of synthetic rubber. The glue required to do the job right is harmful to you and to the environment, and it's replacement is lacking in it's ability to always provide a good seal. However, if you don't have a new tube handy, you will have no choice so we explain how to do it below.

Bicycle tube replacement kit

You will need several items to do the job right.

1 - An adjustable wrench to remove the wheel if you don't have quick release wheel
2 - A set of tire irons to remove the tire. They are usually sold in a set of 3
3 - A spare inner tube
4 - A patch kit for tire repair if necessary
5 - A pump or other source of air
6 - An ink pen (yes, an ink pen - you'll see)



Finding the cause of the flat and installing a new tube


Removing the old tube to find the cause of the flat
Step 1 - Let as much of the air out of the tire as possible. The less air in the tube, the easier it is to remove. The tip of a phillips screwdriver works well, or you can use a corner of a tire iron.
Removing the old tube Step 2 photo


Step 2 - Working on the part of the wheel furthest from the valve, hold the tire away from the edge of the rim with your thumb and insert the spoon shaped end of a tire iron with the curved edge facing the tire. Note: if tire sticks to the edge of the rim, it's best to break that 'seal' all the way around the tire on both sides first by pressing the tire away from the side of the rim with your thumbs. Slide the tire iron up under the tire just enough that it won't slip out.
Removing the old tube Step 2a photo



Step 2a - You should now be able to slide the iron around the edge of the rim gradually releasing the tire until you have completely circled the rim. At this point, the half the tire facing you should be off the rim..
Removing the old tube Step 2b photo

Step 2b - If the tire is real tight, you can lock the other end of the tire iron around one of the spokes and repeat this step with a second tire iron starting about 2 or 3 inches from the position of the first tire iron. Make sure that the first one is tucked up under your arm or hold it in place with your other hand so that if it breaks free, it won't fly up into your face.
Removing the old tube Step 3 photo

Step 3 - Hold the wheel so that you're looking at the area where the valve goes through the rim. Starting from the part of the wheel furthest from the valve, start removing the tube. When just the valve remains in the rim, press the tire out of the way with your thumb. Take an ink pen (told ya) and mark a circle on the side of the tire and on the side of the tube itself where the valve goes through the rim. This is an important step in that it will help you locate the cause of the flat. With the tire still pressed out of the way, slide the valve out of the rim.

Step 4 - Now you want to locate the hole in the tube. Fill the tube with air. If the hole is large, it's location will be obvious. If not, keep putting air in until the tube expands beyond it's normal size,within reason, you're not trying to create a blimp. Starting at the valve, hold the outside side of the tube close to your cheek and slowly rotate the tube until you can feel the air leaking from the hole. If you can't find the leak you might have what's called a 'high pressure' leak. It's called this because the hole is so small it won't start leaking enough to find by this method until you have 20 or more pounds of air in the tube. Since you can only put about 5 pounds of air in a tube when it's out of the tire, you may not feel the leak. Fill a sink with water deep enough that you can submerge about 1 foot of the tube at a time. Slowly pass the tube through the water watching closely for air bubbles.Once you find the hole by one of these methods, mark a circle around it with an ink pen. Make the circle fairly large otherwise when you let the air out of the tube, it will be hard to find.
Removing the old tube Step 5 photo

Step 5 - Now that you know where the hole is located on the tube, you can find what caused the flat. At this point most people will tell you to run your finger around the inside of the tire to find it, but that's kind of silly. If the flat was caused by a small nail or most likely a piece of glass, you'll cut your finger. But you were smart enough to mark the position of the tube in the tire with a circle, so let enough air out of the tube that it takes it's normal shape. Lay the wheel on a flat surface with the open side of the tire facing you, making sure the circle you made on the tire lines up with the valve hole. Lay the tube on the wheel with the tube in it's original position as indicated by the circle by the valve.
Removing the old tube Step 5a photo


Step 5a - Find the circle you marked around the hole in the tube. Now mark an X on the side of the tire at the location of the hole. Now you know exactly where to look for what caused the flat without causing bodily injury.
Step 6 - If the hole is on the outside of the tube or along one side of it, inspect the tire thoroughly inside and out around the area where you marked the X until you find the culprit or the cut or hole it left. Take your time with this inspection. With today's 'knobby' style tires, small pieces of wire and glass have plenty of places to hide. If the hole was on the inside edge of the tube, inspect the rim for any sharp points or spokes poking through. If you still can't find what caused the flat, check out Other possibilities.
Step 7 - If the hole or cut in the tire is very small, you can skip to If the hole is relatively small, you can put a patch inside the tire and move on. If it's too large to patch effectively, get yourself a new tire and proceed to Part 2. If the problem is on the wheel rim itself, grind down the spoke or file down the imperfection.

Installing the new tube.
Installing the new tube Step 1 photo

Step 1 - If you had to remove the tire, put it back on making sure to leave one side open for the tube. Inflate the new tube just enough that it takes it's normal shape. With the open side of the tire facing you, find the valve hole in the rim and press the tire out of the way just enough to expose the valve hole. Slide the valve through the hole in the rimstrip and all the way down through the valve hole.(if the valve doesn't slide through the rimstrip easily, use a small screwdriver to lift it away from the rim just far enough to let the valve slide all the way through then slide the valve through the valve hole)
Installing the new tube Step 2 photo

Step 2 - Lay the wheel down on a flat surface with the open side of the tire facing you. Starting at the valve hole, gradually work the tube up inside the tire and onto the rim until the whole tube is inside the tire and seated fully on the rim. Make sure to work the tube in from both sides of the valve position using both hands at the same time.
Installing the new tube Step 3 photo

Step 3 - Beginning at the valve position, press the bead of the tire inside the wall of the rim. Do this on both sides of the valve for a good 6 to 8 inches. Important. Grab the tip of the valve and work it in and out of the valve hole a few times until the valve slides in and out easily. This assures you that the part of the tube around the valve isn't stuck between the tire and the rim.
Installing the new tube Step 4-1 photo

Installing the new tube Step 4-2 photo





Step 4 - Continue working the tire onto the rim using both hands at the same time. As it becomes harder to work the tire in, let some of the air out of the tube. If you're working with a mountain bike tire or some of the cross tires you should be able to work the whole tire onto the rim with just your hands. If this is the case, move on to Step 5.
Installing the new tube Step 4a photo

Step 4a - If you're working with a road bike tire or a tighter cross tire, you probably won't be able to get the tire all the way on. Work the tire on as far as you can hopefully leaving only about 8 or 10 inches to go. Holding the tire tight against the rim with your left hand (if you are right handed or right hand if you are left handed) on one side of the remaining portion, place the a tire iron under the exposed lip of the tire about an inch from your hand with the curved side of the iron facing the rim. Pry the tire onto the rim. Gradually move your hand and the tire iron along the rim an inch at a time until the whole tire is on the rim. Important. Make sure that each time you pull the tire iron out that you do it slowly and try to pull it out using a motion just the opposite of the prying motion. This will hopefully prevent you from pinching the tube between the tire and the rim.
Installing the new tube Step 5-1 photo

Installing the new tube Step 5-2 photo







Step 5 - Once the tire is on the rim, put just enough air in that the tire seats itself on the rim. You may have to squeeze the tire at the valve to keep the valve from being pushed inside the tire. Important. Once you have some air in the tire push the valve in and out a few times to make sure it's not stuck in the tire.
Installing the new tube Step 6-1 photo

Installing the new tube Step 6-2 photo







Step 6 - Important. Using any line on the tire that runs parallel to the rim, check both sides of the tire to make sure the tire has seated evenly all the way around. If the tire is not seated properly, it could blow off the rim when you inflate it fully. If you find any 'low' spots, use the heel of your hands to push the tire to it's proper position.
Step 7 - Put some more air in and check both sides of the tire again. If all looks good, inflate the tire to it's full pressure, checking both sides one more time once this is done. Sometimes you might hear the tire 'pop' into place, but that's normal.
Now, you're good to go.
This is a fairly comprehensive tutorial on fixing flats. If you would like a printable copy of the information above without the pictures and extended explanations to take with you on your bike, Click Here.
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Patching a tube
Inner tube patch kit photo



The first thing you'll need is a patch kit. A decent patch kit will run you about 3 or 4 dollars. It should include an assortment of patches, a tube of glue and a piece of sandpaper or some type of scraper.
Once you've located the hole in the tube, you need to use the sandpaper or scraper to rough up the area around the hole. You don't need to rough it up too much, just enough to remove and oils and leave a scored surface. Make sure you rough up an area a little larger than the patch. Put some glue on the tube and smear it around with your finger until it's spread evenly and covers an area slightly larger than the patch.

Let the glue set up for several seconds until it's tacky to the touch. Press the patch onto the tube making sure you press down on the whole patch. Hold the patch in place until the glue dries a bit more. The longer you let the glue dry, the better. It's preferable to let the patch sit overnight with some weight on it, but if you're in a hurry, give it at least 5 minutes or until the glue is opaque and dry to the touch.

Once the glue is dry, bend the patch slightly to crack the plastic film then carefully remove the plastic film from the exposed side of the patch. If the colored outer edge of the patch sticks to the plastic film, you need to let it dry longer. You can also try removing the plastic film from another side of the patch. Once you have removed it, make sure the colored edge is attached to the tube with no bubbles of loose edges. If this is the case, smooth the bubble(s) out and apply a little glue to any part of the edge that didn't stick and let it dry thoroughly.

Put the tube back in the tire, air it up, and hope for the best. You may have to do this a few times to get the hang of it. And again, it's best to let the glue dry for as long as you can.

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Other Possibilities
1 - Broken bead: The part of the tire that sits in the rim and gives the tire it's shape is called the bead. In most cases the bead is made of stranded wire. Once in a while, usually in an older tire, one of the strands can break and poke through the rubber surrounding it. If the flat occurred on the side of then tube, check the bead in that area. Also make sure that the rubber of the tire fully surrounds the bead on both sides of the tire.

2 - High Pressure leak: Basically, a high pressure leak is a hole in the tube that is so small that air does not escape through it until there is a lot of pressure in the tire. A telltale sign of this kind of leak is a tire that loses a lot of air in a short amount of time such as overnight. These kinds of holes are hard, if not impossible to find. If you checked your tube under water and still did not find the hole, your only recourse is to put in a new tube.

3 - Loose spoke: If the hole in your tube is on the inside surface and you've already checked for rough surfaces on the rim and spokes poking through, check for a loose spoke. Sometimes a loose spoke can 'float' around in the rim and can puncture the tube. If you find a loose spoke, tighten it in a counterclockwise direction (while looking at the side of the nipple) with your fingers just enough so it doesn't move around in the rim. If you tighten it too much you could mess up the alignment of the rim. You should also consider bringing your wheel in to a bike shop to have that spoke tightened properly to avoid this problem in the future.

4 - Low air pressure: If you ride your bike with low air pressure in your tires, each time you start and stop, the tire slides on the rim a minute amount. This can cause friction between the tube and the tire or rim gradually wearing a hole in the tube. Telltale signs of this problem are abrasion marks around the hole in the tube. If you ride often, you should check the air pressure in your tires at least once every week or two. If you only ride occasionally you should check it each time you ride.

5 - Debris in the tire: If you see the above mentioned abrasion marks and low air pressure is not your problem, you might have bits of debris floating around inside your tire. This debris can be small particles of sand, dirt or in older tires, pieces of rubber that have broken off from the tire. Hold the tire upright and shake it gently a few times. If you find debris building up on the bottom inside of the tire, this could be your problem. If this is the case, shake the tire roughly to remove the debris and using a slightly damp rag, wipe out the inside of the tire. Make sure the tire dries before putting it back on the wheel.

6 - The base of the air valve: Twist the air valve around in circles watching for any cracks or listening for that hiss of leaking air at it's base. If you find a crack it could mean one of two things. One, you're not riding with enough air pressure in your tire which can cause the valve to rock back and forth slightly each time you start and stop. Over time the metal of the rim around the valve hole can wear through the base of the valve. The solution to this problem is easy, check your air pressure often. Two, if you have a valve that tightens to the rim with a nut or splined fastener, each time you start and stop, since the valve is anchored to the rim, the tube is stressed around the base of the valve. The solution to this problem is to toss the nut or fastener away or to get a second one and lock the two together leaving a slight gap between them and the rim.





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